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Li, Chenzhao, Shengwen Liu, Yachao Zeng, Yadong Liu, David A. Cullen, Gang Wu, and Jian Xie. "Rationally Designed PGM-Free Catalyst MEA with Extraordinary Performance." ECS Meeting Abstracts MA2022-02, no. 40 (October 9, 2022): 1487. http://dx.doi.org/10.1149/ma2022-02401487mtgabs.
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Platinum group metal (PGM) catalysts are the major electrocatalysts for oxygen reduction reaction (ORR) in the polymer electrolyte membrane fuel cells (PEMFCs). However, the high cost of PGM catalysts is the major huddler for the widespread applications of fuel cell electric vehicles. To remove this cost obstacle of fuel cell commercialization, PGM-free catalysts have been considered as the replacement of PGM catalysts for ORR because of the low cost and relatively comparable performance with PGM catalyst. Fe-C-N complex is the one of the most active centers in PGM-Free catalyst groups. This type of catalyst shows excellent activity characterized using the rotation disk electrode (RDE), i.e., the half wave potential (E1/2 ) could reach 0.91 V versus standard hydrogen electrode (SHE). However, in a membrane electrode assembly (MEA), the performance of PGM-Free catalysts cannot achieve the comparable performance to PGM catalyst. Since there are so many differences between PGM-free, and PGM catalysts e.g., activity, stability, surface conditions, particle size etc. The fabrication of PGM-Free catalyst MEA cannot simply borrow the methods from that of making PGM MEA. In addition, the thicknesses of catalyst layers of PFM-free are significantly thicker than that of PGM, i.e., 10 times. Hereby, we proposed a novel method of fabricating PGM-Free catalyst MEA, so that the intrinsic catalyst activity from RDE can be translated into MEA performance. The method is based on the catalyst coated membrane (CCM) method using optimized ionomer to carbon (I/C) ratio and solvent mixture of catalyst ink. Such method pushes PGM-free MEA first ever achieved the current density of 50.8 mA cm-2 at 0.9 V iR-free in H2/O2 and over 150 mA cm-2 at 0.8 V in H2/air, which surpassed the 2025 performance targets of US Department of Energy (DOE) for PGM-Free catalyst MEA. Further, the property (solvent composition, dispersion of catalyst and ionomer in an ink), structure (pore structure) and the MEA performance have been characterized using mercury intrusion porosimetry (MIP), MEA testing. A property-structure-performance relationship has been established.
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Men Truong, Van, Julian Richard Tolchard, Jørgen Svendby, Maidhily Manikandan, Hamish A. Miller, Svein Sunde, Hsiharng Yang, Dario R. Dekel, and Alejandro Oyarce Barnett. "Platinum and Platinum Group Metal-Free Catalysts for Anion Exchange Membrane Fuel Cells." Energies 13, no. 3 (January 27, 2020): 582. http://dx.doi.org/10.3390/en13030582.
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The development of active hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) catalysts for use in anion exchange membrane fuel cells (AEMFCs), which are free from platinum group metals (PGMs), is expected to bring this technology one step closer to commercial applications. This paper reports our recent progress developing HOR Pt-free and PGM-free catalysts (Pd/CeO2 and NiCo/C, respectively), and ORR PGM-free Co3O4 for AEMFCs. The catalysts were prepared by different synthesis techniques and characterized by both physical-chemical and electrochemical methods. A hydrothermally synthesized Co3O4 + C composite ORR catalyst used in combination with Pt/C as HOR catalyst shows good H2/O2 AEMFC performance (peak power density of ~388 mW cm−2), while the same catalyst coupled with our flame spray pyrolysis synthesised Pd/CeO2 anode catalysts reaches peak power densities of ~309 mW cm−2. Changing the anode to nanostructured NiCo/C catalyst, the performance is significantly reduced. This study confirms previous conclusions, that is indeed possible to develop high performing AEMFCs free from Pt; however, the challenge to achieve completely PGM-free AEMFCs still remains.
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Zhang, Hanguang, and Piotr Zelenay. "Platinum Group Metal-Free ORR Catalysts for Anion Exchange Membrane Fuel Cells." ECS Meeting Abstracts MA2022-02, no. 40 (October 9, 2022): 1486. http://dx.doi.org/10.1149/ma2022-02401486mtgabs.
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Platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) have attracted significant attention in the last two decades. These catalysts typically perform better in alkaline aqueous electrolytes than in their acidic counterparts.1, 2 However, the performance of PGM-free ORR catalysts in anion exchange membrane fuels cells (AEMFCs) have been consistently lower than in the acidic polymer electrolyte fuel cells (PEFCs). The most likely reasons for the sub-par behavior of PGM-free catalysts in AEMFCs has been often linked to difficulties in preparing electrodes with anion exchange ionomers and assuring efficient water management. These challenges have been amplified by the high-loading requirement for PGM-free ORR catalysts, resulting in electrodes by as much as an order of magnitude thicker than the PGM-based ones. In this presentation, we will demonstrate AEMFCs with much improved performance of the PGM-free cathode (Fe-N-C catalyst-based). The performance improvement has been achieved by optimizing the electrode fabrication process, including changes to the electrode configuration and catalyst ink preparation. These changes have allowed us to elevate the AEMFC performance, including the peak power density of > 0.8 W cm-2 in H2-O2 cells, to the level comparable to that of the corresponding PEFC, operating with a PGM-free cathode under the same operating conditions. References: 1. Li, X.; Liu, G.; Popov, B. N., Activity and stability of non-precious metal catalysts for oxygen reduction in acid and alkaline electrolytes. Journal of Power Sources 2010, 195 (19), 6373-6378. 2. Choi, C. H.; Lim, H.-K.; Chung, M. W.; Chon, G.; Ranjbar Sahraie, N.; Altin, A.; Sougrati, M.-T.; Stievano, L.; Oh, H. S.; Park, E. S.; Luo, F.; Strasser, P.; Dražić, G.; Mayrhofer, K. J. J.; Kim, H.; Jaouen, F., The Achilles' heel of iron-based catalysts during oxygen reduction in an acidic medium. Energy & Environmental Science 2018, 11 (11), 3176-3182.
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Damjanović, Ana Marija, Burak Koyutürk, Yan-Sheng Li, Davide Menga, Christian Eickes, Hany A. El-Sayed, Hubert A. Gasteiger, Tim-Patrick Fellinger, and Michele Piana. "Loading Impact of a PGM-Free Catalyst on the Mass Activity in Proton Exchange Membrane Fuel Cells." Journal of The Electrochemical Society 168, no. 11 (November 1, 2021): 114518. http://dx.doi.org/10.1149/1945-7111/ac3779.
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Platinum-group-metal-free (PGM-free) catalysts are currently considered as potential oxygen-reduction-reaction (ORR) catalysts to replace costly and supply-limited platinum at the cathode side of proton exchange membrane fuel cells (PEMFCs). Extensive research efforts have led to substantial progress with regards to the ORR activity of PGM-free ORR catalysts, but there is uncertainty about the dependence of the mass activity on the catalyst loading. In this study, the effect of catalyst loading on the mass activity is investigated by means of rotating disk electrode measurements as well as single cell PEMFC tests using a commercial PGM-free ORR catalyst. Single cell tests with a wide range of loadings (0.4–4.0 mgcat cm−2 MEA) are compared to rotating disk electrode measurements with low loadings of 40–600 μgcat cm−2 disk. In contrast to indications in the literature that the ORR activity depends on catalyst loading, our results reveal an independence of the ORR mass activity from the catalysts loading in both RDE and PEMFC tests, if corrections for the voltage losses in H2/O2 single cell tests are considered. Moreover, no clear relation of the stability to the catalyst loading was found in H2/O2 PEMFCs.
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Moschkowitsch, Wenjamin, and Lior Elbaz. "(Digital Presentation) Ternary Nifetiooh Catalyst for the Oxygen Evolution Reaction: Study of the Effect of the Addition of Ti at Different Loadings." ECS Meeting Abstracts MA2022-01, no. 41 (July 7, 2022): 2440. http://dx.doi.org/10.1149/ma2022-01412440mtgabs.
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Ternary NiFeTiOOH Catalyst for the Oxygen Evolution Reaction: Study of the Effect of the Addition of Ti at Different Loadings Wenjamin Moschkowitsch and Lior Elbaz Chemistry Department, Bar-Ilan University, Ramat-Gan 5290002, Israel The demand for energy is expected to grow rapidly in the next decades, but it cannot be solely fulfilled with fossil fuel-based technologies without having a huge impact on the environment. The shift to production of clean energy from alternative sources, such as wind and sun, raise the importance of energy storage technologies. One of the most prominent solutions is storing surplus energy, harvested at peak production times and seasons, in hydrogen. However, the production of hydrogen with methods that require as little energy as possible, as well as being sustainable, environmentally friendly and cheap, are still considered to be a big challenge. Water electrolysis is the simplest industrial process for hydrogen production, and can be linked to fuel cells technology. Among the available electrolyzers, alkaline electrolyzers (ALE) are considered state-of-the-art. Although they can work with platinum-group metal-free (PGM-free) catalysts, unfortunately, this technology still requires the use of PGM catalysts in order to increase the current density, and lower the reaction activation energy. In electrolyzers, water splits into oxygen and hydrogen in two separate reactions, taking place at the anode and cathode. The cathodic reaction is the Hydrogen Evolution Reaction (HER), which is considered to be relatively facile. The anodic, Oxygen Evolution Reaction (OER), is considered to be much more difficult, since it is a four-electron process with very sluggish kinetics. The best known catalysts for this reaction in acidic medium are IrO2 and RuO2, oxides of very rare and precious metals (Ir is the scarcest metal on earth’s crust). In addition, in acidic medium, most PGM-free catalysts, based on earth abundant elements, are considered unstable (these conditions have also shown to be detrimental for Ir and Ru-based catalysts). In contrast, in ALEs, PGM-free catalysts have shown to be a good alternative to PGM catalysts. The most common OER PGM-free catalysts are first-row transition metals in their oxide, hydroxide and oxyhydroxide forms.One such catalyst is nickel oxyhydroxide (NiOOH). The structure of this specific catalyst has been studied in great detail by many different research groups, yet there are several open questions regarding the OER mechanism, i.e. the exact catalytic center and active phase.Recent studies suggest that pure NiOOH is not very active at all, and that all of the activity can be attributed to iron impurities.Indeed, NiFeOOH with iron content of 15-25 %at, has a much higher activity and a much lower overpotential compared to other PGM-free catalysts. It can thus be regarded as a benchmark for this class of OER catalysts.It is well accepted by now that the bimetallic catalyst further increases the intrinsic catalytic activity, and that addition of other transition metals,can further increase it.
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Elbaz, Lior, and Rifael Z. Snitkoff-Sol. "(Invited) Elucidating the Electrochemically Active Site Density of PGM-Free ORR Catalysts in Situ Fuel Cells Using Fourier Transform Alternating Current Voltammetry." ECS Meeting Abstracts MA2022-01, no. 49 (July 7, 2022): 2059. http://dx.doi.org/10.1149/ma2022-01492059mtgabs.
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The rising interest in polymer electrolyte fuel cell (PEFC) technology, part of the global shift in energy production to clean sources, is accompanied by efforts to drive down the cost of this technology, which focus primarily on the cathode catalyst, the most expensive PEFC component. While platinum-group metals (PGMs) continues to be the materials of choice for oxygen reduction reaction (ORR) catalysts, use of these materials in PEFCs must be significantly reduced or eliminated without a penalty in the overall cell performance for PEFC technology to become fully viable. The most promising class ORR catalysts that do not utilize PGMs (i.e., PGM-free catalysts), involve first-row transition metals, such as iron and cobalt incorporated in a nitrogen-doped carbon (M-N-C catalysts). While advancements in M-N-C activity have been impressive, the much sought-after improvement in durability has been impeded by limited information on changes in the PGM-free catalyst active site density, activity and its degradation rate during fuel cell testing. Currently, degradation of PGM-free catalysts during fuel cell operation is often quantified using the low-current region of polarization curves. While this approach is well established, it neglects complications from such factors as catalyst pore structure, membrane conductivity, ionomer content, nature of the support, and the inhomogeneity of active sites. Hence, there exists a critical need for a method with high specificity towards catalytic activity. In this presentation we will report for the first time on the use of Fourier-transform alternating current voltammetry (FTacV) as an electrochemical method for accurately quantifying the electrochemically active site density of PGM-free ORR catalysts and following their degradation in situ during operation of polymer electrolyte fuel cells. Using this method, we were able to detect changes in performance of electrochemically active species (electrocatalytic centers in this case), allowing us to calculate the electrochemical active site density (EASD) for the first time, which is necessary to elucidate the degradation mechanisms of PGM-free ORR catalysts that occur in situ fuel cells. large-amplitude FTacV, a well-established electrochemical method with distinct advantages over dc methods, was utilized to quantify the electrochemically active site density of PGM-free FeNC catalysts in situ in PEFC. First, we will demonstrate that an accurate measurement of the EASD can be made using this method. To further emphasize the strength of the technique, we will present our findings during degradation of commercial FeNC catalysts in operating PEFC. The peak currents from higher harmonics produced by this method are correlated to the fuel cell performance, and decrease after durability tests in a manner that indicates EASD loss may not be the only catalyst degradation mechanism, thus inviting further studies of yet-unknown degradation pathway(s).
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Zhang, Hanguang, Hoon T. Chung, David A. Cullen, Stephan Wagner, Ulrike I. Kramm, Karren L. More, Piotr Zelenay, and Gang Wu. "High-performance fuel cell cathodes exclusively containing atomically dispersed iron active sites." Energy & Environmental Science 12, no. 8 (2019): 2548–58. http://dx.doi.org/10.1039/c9ee00877b.
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Platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) with atomically dispersed FeN4 sites have emerged as a potential replacement for low-PGM catalysts in acidic polymer electrolyte fuel cells (PEFCs).
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Zhong, Sichen, Judith Lattimer, Derek James Strasser, James McKone, Manjodh Kaur, Keda Hu, and Yushan Yan. "PGM-Free AEM Electrolyzer Cell Development for Solar Power Integration." ECS Meeting Abstracts MA2022-02, no. 44 (October 9, 2022): 1688. http://dx.doi.org/10.1149/ma2022-02441688mtgabs.
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The increasing availability of renewable energy sources, especially solar power, coupled with the desire to reduce greenhouse gas emissions, has led to an increased interest in using renewables to satisfy global energy demand. Hydrogen is an attractive alternative to fossil fuels due to its potential for emissions reductions and advantages in storage and transportation. Direct solar-to-hydrogen generation would enable the conversion of renewable energy and water into a storable fuel, thereby drastically reducing carbon emissions. However, current hydrogen production from commercial PEM electrolysis systems requires acidic environment which necessitates the use of expensive platinum group metal (PGM) catalysts and corrosion resistant cell stack components. Thus, a stable, robust, and inexpensive anion exchange membrane and PGM-free catalysts are needed to make alkaline solar water splitting commercially viable as a replacement for the expensive PEM system. We have developed a fully PGM-free electrolyzer using anion exchange membrane (AEM) in an alkaline environment that operates at 80 °C. Using carbon supported NiMo as hydrogen evolution reaction (HER) catalyst and NiFe as oxygen evolution reaction (OER) catalyst, in combination with commercially available AEM from Versogen, we were able to achieve a stable performance of 1.504 V at 100 mA/cm2, compared with baseline PGM cell at 1.508 V, in alkaline environment. At 2 A/cm2, the fully PGM-free cell demonstrated 200 mV higher potential compared to the PGM baseline cell at 2.009 V. Furthermore, we were able to run more than 200-hour at constant current density 2 A/cm2, with 85 mV performance loss. Further developments in catalyst performance and membrane stability, as well as integration with photovoltaics to enable hydrogen production from water, are underway. Acknowledgement: The project is financially supported by the Department of Energy’s Office of Science under the Grant DE-SC0020576
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Du, Lei, Gaixia Zhang, and Shuhui Sun. "Proton Exchange Membrane (PEM) Fuel Cells with Platinum Group Metal (PGM)-Free Cathode." Automotive Innovation 4, no. 2 (April 28, 2021): 131–43. http://dx.doi.org/10.1007/s42154-021-00146-0.
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AbstractProton exchange membrane (PEM) fuel cells have gained increasing interest from academia and industry, due to its remarkable advantages including high efficiency, high energy density, high power density, and fast refueling, also because of the urgent demand for clean and renewable energy. One of the biggest challenges for PEM fuel cell technology is the high cost, attributed to the use of precious platinum group metals (PGM), e.g., Pt, particularly at cathodes where sluggish oxygen reduction reaction takes place. Two primary ways have been paved to address this cost challenge: one named low-loading PGM-based catalysts and another one is non-precious metal-based or PGM-free catalysts. Particularly for the PGM-free catalysts, tremendous efforts have been made to improve the performance and durability—milestones have been achieved in the corresponding PEM fuel cells. Even though the current status is still far from meeting the expectations. More efforts are thus required to further research and develop the desired PGM-free catalysts for cathodes in PEM fuel cells. Herein, this paper discusses the most recent progress of PGM-free catalysts and their applications in the practical membrane electrolyte assembly and PEM fuel cells. The most promising directions for future research and development are pointed out in terms of enhancing the intrinsic activity, reducing the degradation, as well as the study at the level of fuel cell stacks.
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Arman, Tanvir Alam, Aman Uddin, Shuo Ding, Yanghua He, Cankur Cetinbas, Jui kun Peng, Xiaohua Wang, et al. "Patterned Nafion Membranes for Improved Transport in PGM-Free PEMFC Cathodes." ECS Meeting Abstracts MA2022-02, no. 39 (October 9, 2022): 1429. http://dx.doi.org/10.1149/ma2022-02391429mtgabs.
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Substantial cost reduction is needed to commercialize polymer electrolyte fuel cells. As PGM catalysts are projected to account for ~42% cost of a fuel cell stack (1), replacement of PGMs with PGM-free catalysts is an attractive route to cost reduction. Over the past decade, extensive research efforts have led to significant improvements in kinetic activity (2), but conventional PGM-free catalyst continues to have lower volumetric activity than PGM catalysts. The lower volumetric activity requires use of a thicker cathode catalyst layer (CL), resulting in significant proton and oxygen transport losses (3). Therefore, along with kinetic improvements in oxygen reduction reaction, improved transport of H+ and O2 is needed to achieve performance comparable to PGM catalyst. In this study, we adopt a micro-patterning technique to incorporate non-tortuous ionomer channels in the cathode to increase the ionic conductivity of the thick catalyst layer. As shown in Figure 1, cathode ionomer channels enable rapid transportation of H+ throughout the catalyst layer, compared to thin and tortuous ionomer films in the conventional electrode. Polarization curves obtained in H2/air show significantly higher performance for the CL with ionomer channels compared to the conventional cathode. Electrochemical impedance spectroscopy data in H2/N2 also demonstrate a significant decrease in H+ resistance in the catalyst layer. The ionomer channels lead to a reduction in the H+ transport resistance, reducing ohmic overpotential in the catalyst layer. Further improvement in performance in the mass transport region is achieved through implementing optimized design of the dedicated ionomer channel. Acknowledgment This research was supported by the US Department of Energy, the Office of Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office and the LANL LDRD program. References D. Papageorgopoulos, DOE Hydrogen and Fuel Cells Program FY2019 Annual Merit Review Proceedings, https://www.hydrogen.energy.gov/pdfs/review19/plenary_fuel_cell_papageorgopoulos_2019.pdf (2019). H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao and G. Wu, (2017). S. Komini Babu, H. T. Chung, P. Zelenay and S. Litster, ACS Appl Mater Interfaces, 8, 32764-32777 (2016). Figure 1
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Osmieri, Luigi, Yanghua He, Haoran Yu, David A. Cullen, and Piotr Zelenay. "PGM-Free Catalysts and Electrodes for Anion Exchange Membrane Water Electrolyzers." ECS Meeting Abstracts MA2022-02, no. 44 (October 9, 2022): 1674. http://dx.doi.org/10.1149/ma2022-02441674mtgabs.
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Recent progress in the development of anion exchange membranes (AEMs) with improved performance and durability has opened the way for the application of the AEM-based electrolyzers in low-temperature water electrolysis (LTWE),1 an important technology for producing “green” hydrogen.2 AEM-LTWEs can potentially operate on pure water, i.e., without highly concentrated and corrosive supporting electrolyte, and they allow for replacement of electrocatalysts based on platinum group metals (PGMs) with PGM-free ones, thus addressing the main drawbacks of the liquid-alkaline (LA) and proton exchange membrane (PEM) electrolyzers.3 Consequently, the development of PGM-free electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media is of primary importance for the deployment of AEM-LTWEs that has attracted significant attention of researchers.4–6 Besides improving the catalytic activity, the integration of PGM-free HER and OER electrocatalysts into electrodes for operation in AEM electrolyzers is crucial to achieving satisfactory electrolyzer performance and making them competitive with the LA and PEM systems.7,8 In this work, we measured electrocatalytic activity of a series of OER and HER catalysts in a three-electrode cell and then implemented these catalysts in electrodes for testing in an AEM electrolyzer. We investigated different classes of OER catalysts, including commercial IrO2 (a PGM ORR benchmark), LaxSr1-xCoO3-δ oxides, Ni-Fe nanofoam oxides, Ni-Fe aerogel-derived oxides, and MOF-derived Co oxides. In the HER-catalyst part of the study, we compared a commercial PtRu/C (a PGM HER benchmark) with an aerogel NiMo/C catalyst. Catalysts and electrodes before and after testing were characterized by XRD, SEM, EDS, and XPS. In addition to exploring different catalysts, we investigated the impact of several fabrication variables such as the ink deposition method, amount of ionomer, incorporation of a binding agent, and the type of anode porous transport layer on performance. The tests were carried in an electrolyzer operating with pure water and two electrolyte solutions, 0.1 M KOH and 1% K2CO3. The results show that, in addition to the OER and HER electrocatalytic activity, the electrode fabrication is an important factor affecting AEM electrolyzer performance, especially in the pure-water operation mode, in which case assuring an effective transport of the OH– ions within the catalyst layer is especially challenging. References Y. S. Kim, ACS Appl. Polym. Mater. (2021). C. Santoro et al., ChemSusChem, 202200027 (2022). H. A. Miller et al., Sustain. Energy Fuels, 4, 2114–2133 (2020). D. Xu et al., ACS Catal., 9, 7–15 (2019). H. Shi et al., Adv. Funct. Mater., 2102285, 1–10 (2021). H. Doan et al., J. Electrochem. Soc., 168, 084501 (2021). N. U. Hassan, M. Mandal, B. Zulevi, P. A. Kohl, and W. E. Mustain, Electrochim. Acta, 409, 140001 (2022). G. A. Lindquist et al., ACS Appl. Mater. Interfaces (2021).
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Zachman, Michael J., Haoran Yu, Shengwen Liu, Yachao Zeng, Yi Li, Gang Wu, and David A. Cullen. "Advanced Electron Microscopy Techniques for PGM-Free Catalyst Characterization." ECS Meeting Abstracts MA2022-02, no. 39 (October 9, 2022): 1447. http://dx.doi.org/10.1149/ma2022-02391447mtgabs.
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Hydrogen fuel cells currently rely on expensive platinum group metal nanoparticle catalysts [1]. For green hydrogen production and utilization to become widely commercially viable, the cost of the devices that produce and utilize hydrogen must be significantly reduced. Platinum group metal-free (PGM-free) catalysts have the potential to greatly reduce this cost, and materials consisting of single transition metal atoms embedded in a nitrogen-doped graphitic carbon structure have shown particular promise for use as fuel cell cathodes [2]. A better understanding of the active site properties in these materials is still needed, however, to improve their stability and design new active site structures with enhanced properties [3]. Due to the atomic-scale nature of the active sites in these materials, scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) have proven invaluable for demonstrating their atomically dispersed nature and composition [4]. Conventional STEM techniques have limited ability to correlate the local bonding environment and oxidation state of the metal atoms, for example, or track changes in the catalyst structure both during synthesis and as a result of cycling, which would provide a deeper understanding of the relationship between active site and catalyst properties. Here, we demonstrate advanced electron microscopy techniques that provide both enhanced and previously inaccessible information about PGM-free catalysts and their active sites. We show developments in automated identification of metal atom positions, which we use both to generate statistics about interatomic distances and to automatically position the STEM probe on individual atoms for EELS data acquisition. The former allows information about the presence of dual-metal site structures to be extracted, for example, and the latter allows compositional information with improved SNR to be obtained. Rapid automatic probe positioning also presents the opportunity for measuring the effect of local bonding environment on metal atom oxidation state, which cannot be obtained manually since these sites are typically unstable under the beam. In addition, we will show identical-location STEM (IL-STEM) techniques that allow the evolution of catalyst morphology and properties to be tracked at high resolution across synthesis steps and accelerated stress tests [5]. In particular, we use IL-STEM imaging and EELS to track deposition of graphitic material on the surface of a PGM-free catalyst that significantly improves the material’s durability, as well as track the change in the nanoscale graphitic carbon structure of the material as a function of electrochemical cycling. By providing access to enhanced compositional and bonding state information, as well as the ability to track properties as a material evolves, these techniques will advance our knowledge of PGM-free catalysts and enable better control over their properties in the future, accelerating wide-spread use of hydrogen fuel cells [6]. References: [1] D.A. Cullen et al., Nat. Energy 6, 462 (2021). [2] G. Wu, Front. Energy 11, 286 (2017). [3] U. Martinez et al., Adv. Mater. 31, 1806545 (2019). [4] H.T. Chung et al., Science 357, 479 (2017). [5] H. Yu et al., ACS Appl. Mater. Interfaces (2022). [6] This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the Electrocatalysis (ElectroCat) consortium. Electron microscopy research was supported by the Center for Nanophase Materials Sciences (CNMS), which is a US Department of Energy, Office of Science User Facility at Oak Ridge National Laboratory.
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Adabi Firouzjaie, Horie, Abolfazl Shakouri, Christopher Williams, John R. Regalbuto, Alexey Serov, William Earl Mustain, Andrea Zitolo, Tristan Asset, Frederic Jaouen, and Horie Adabi Firouzjaie. "Multi-Atom PGM Based Catalyst for Highly Efficient Oxygen Reduction Reaction(ORR) and Hydrogen Oxidation Reaction (HOR) in Alkaline Environment." ECS Meeting Abstracts MA2022-02, no. 39 (October 9, 2022): 1439. http://dx.doi.org/10.1149/ma2022-02391439mtgabs.
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Anion exchange membrane fuel cells (AEMFCs) have recently seen significant growth in interest as their achievable current density, peak power density, and longevity have been improved dramatically. Though these advances in performance have been important for demonstrating the feasibility of the technology, nearly all AEMFCs reported in the literature have required a relatively high loading of platinum group metal (PGM)-based catalysts at both the anode and cathode electrodes [1]. However, to take command of the low-temperature fuel cell market, AEMFCs cannot simply reach the same performance as incumbent proton exchange membrane fuel cells (PEMFCs), which have had decades of development and investment. AEMFCs must realize their most widely quoted advantage over PEMFCs and be produced at a much lower cost than PEMFCs. The most likely pathway to acceptably low cost will involve reducing the PGM loading in both electrodes. At the cathode, reasonable PGM-free catalysts exist, as will be shown in this work. At the anode; however, there are no practical contenders that exist to replace PGM-based catalysts. Hence, the most practical approach is to create transitional catalysts with ultra-low PGM content until future PGM-free catalysts can be realized. To reduce the platinum group metal (PGM) loading in anion exchange membrane fuel cell (AEMFC) electrodes, it is important to transition to catalysts with very low PGM content, and eventually to create catalysts that are completely PGM-free. One approach that can be used in both cases is to create atomically dispersed metals on a carbon support. In this work, four catalysts were prepared using a new, simple, scalable Controlled Surface Tension (CST) method: Pt/C, Pt/NC, PtRu/C, and PtRu/NC. CST is unique as it allows for a high density of very small multi-atom clusters, facilitated by altering the surface tension in the synthesis medium. The catalysts were physically characterized using a wide array of techniques, including high-resolution Cs aberration-corrected scanning transmission electron microscopy (STEM), extended X-ray absorption fine structure (EXAFS), and X-ray Absorption Near-Edge Structure (XANES). The catalysts were also tested for their oxygen reduction reaction and hydrogen oxidation reaction activity both ex-situ on a rotating ring-disk electrode and in-situ while integrated into the anode (PtRu) and cathode (Pt) of operating AEMFCs. With this new generation of low-PGM materials, it was possible to reduce the PGM loading by a factor of 14 while achieving comparable performance to commercial catalysts with a peak power density approaching 2 W/cm2. AEMFCs were also assembled with ultralow PGM loading (0.05 mgPGM/cm2), where PtRu/NC anodes were paired with Fe–N–C cathodes [2], which allowed for the demonstration of cells with a specific power of 25 W/mgPGM (40 W/mgPt).
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Zeng, Yachao, Qiao Zhi, Chenyu Wang, Chenzhao Li, Hui Xu, David A. Cullen, Deborah J. Myers, Jian Xie, Jacob S. Spendelow, and Gang Wu. "Atomically Dispersed Single Metal Sites for Promoting Pt and Pt3Co Catalysts in Heavy-Duty Meas." ECS Meeting Abstracts MA2022-01, no. 35 (July 7, 2022): 1463. http://dx.doi.org/10.1149/ma2022-01351463mtgabs.
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Significantly reducing platinum group metal (PGM) loading while improving catalytic performance and durability is critical to accelerating proton-exchange membrane fuel cells (PEMFCs) for transportation. Here we report an effective strategy to boost PGM catalysts through integrating PGM-free atomically-dispersed single metal active sites in the carbon support toward the cathode oxygen reduction reaction (ORR). We achieved uniform and fine Pt nanoparticle (NP) (∼2 nm) dispersion on an already highly ORR-active FeN4 site-rich carbon (FeN4–C). Furthermore, we developed an effective approach to preparing a well-dispersed and highly ordered L12 Pt3Co intermetallic nanoparticle catalyst on the FeN4–C support. DFT calculations predicted a synergistic interaction between Pt clusters and surrounding FeN4 sites through weakening O2 adsorption by 0.15 eV on Pt sites and reducing activation energy to break O–O bonds, thereby enhancing the intrinsic activity of Pt. Experimentally, we verified the synergistic effect between Pt or Pt3Co NPs and FeN4 sites, leading to significantly enhanced ORR activity and stability. Especially in a membrane electrode assembly (MEA) with a low cathode Pt loading (0.1 mgPt cm−2), the Pt/FeN4–C catalyst achieved a mass activity of 0.451 A mgPt −1 and retained 80% of the initial values after 30 000 voltage cycles (0.60 to 0.95 V), exceeding DOE 2020 targets. Furthermore, the Pt3Co/FeN4 catalyst achieved significantly enhanced performance and durability concerning initial mass activity (0.72 A mgPt −1), power density (824 mW cm−2 at 0.67 V), and stability (23 mV loss at 1.0 A cm−2). The approach to exploring the synergy between PGM and PGM-free Fe–N–C catalysts provides a new direction to design advanced catalysts for hydrogen fuel cells and various electrocatalysis processes.
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Ul Hassan, Noor, Abolfazl Shakouri, Horie Adabi Firouzjaie, Surachet Duanghathaipornsuk, Barr Zulevi, Paul Kohl, and William Earl Mustain. "High Performance AEM Water Electrolysis with PGM-Free Electrocatalysts." ECS Meeting Abstracts MA2022-02, no. 43 (October 9, 2022): 1620. http://dx.doi.org/10.1149/ma2022-02431620mtgabs.
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Water electrolysis technologies for hydrogen production are getting much attention due to drastic cost reduction in renewable energy sources, like solar, wind, tidal etc. Traditional alkaline water electrolysis has limitations of low current density operation, slow system response and low hydrogen discharge pressure. Proton exchange membrane (PEM) water electrolysis offers compact design, high current density operation, fast system response and pressurized discharge hydrogen. However, PEM electrolyzers require the use of Platinum Group Metal (PGM) based electrocatalysts, expensive perfluorinated membranes and specialized component materials due to its acidic environment. These are all hurdles to its widespread commercial adoption. A relatively new technology, the anion exchange membrane (AEM) electrolyzer can potentially combine benefits from PEM and traditional alkaline electrolyzers, offering high current density operation, pressurized discharge gas and low cost – by utilizing PGM-free electrocatalysts and inexpensive component materials due to the less corrosive alkaline operating environment. However, modern AEM electrolyzers have continued to use high loadings of PGM catalysts in both the cathode and anode. Given the magnitude and recent volatility in the market price of many PGM-group metal catalysts (e.g. Ru, Ir, etc.), it is now even more important for AEM electrolyzers to be realized with significantly lower PGM content – and eventually approaching the complete elimination of PGMs. In this study, we evaluate the performance of several low-PGM and PGM-free electrocatalysts for the oxygen evolution (OER) and hydrogen evolution (HER) reactions for high performance and durability. Here, PGM-free Lanthanum Strontium Cobalt (LSC), Nickel Ferrite (NiFeOx) and low PGM Lead Ruthenate (PbRuOx) were used at the anode for the OER. For the HER cathode, PGM-free Nickel Molybdenum (NiMo) and low-PGM PtNi electrocatalysts were evaluated for their in-situ activity and durability. It will be shown that LSC and NiFeOx show comparable performance to IrOx, with a typical steady-state operating voltage at 60oC and 1.0 A/cm2 (with 0.3 M KOH fed to the anode only) below 1.80 V. Cells with PGM-free anode catalysts were operated stably for over 100 hours. At the cathode, NiMo showed relatively higher overpotentials compared to Pt black, PtNi or Pt/C for the HER. Because of this, various strategies were adopted to reduce the PGM loading while achieving high performance and durable AEM electrolyzer operation. The achieved experimental results provide important insights for the development of AEM based water electrolyzer systems and represent an active step towards its commercial viability.
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Shigapov, A., A. Dubkov, R. Ukropec, B. Carberry, G. Graham, W. Chun, and R. McCabe. "Development of PGM-free catalysts for automotive applications." Kinetics and Catalysis 49, no. 5 (September 2008): 756–64. http://dx.doi.org/10.1134/s0023158408050224.
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Wang, Xiaoping, Magali Ferrandon, Jaehyung Park, Evan C. Wegener, A. Jeremy Kropf, and Deborah J. Myers. "Optimization of Synthesis Variables Towards Improved Activity and Stability of Fe-N-C PGM-Free Catalysts." ECS Meeting Abstracts MA2022-01, no. 35 (July 7, 2022): 1447. http://dx.doi.org/10.1149/ma2022-01351447mtgabs.
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Materials in the Fe-N-C family are the most promising platinum group metal-free (PGM-free) catalysts for the oxygen reduction reaction (ORR) in polymer electrolyte fuel cells (PEFCs).1-3 Although significant progress has been made in recent years in improving both the ORR activity and durability of the Fe-N-C catalysts, further improvements are needed, especially in long-term performance durability in hydrogen-air PEFCs, to enable their use in applications such as propulsion power for light-duty vehicles.3 The most active ORR catalysts in the Fe-N-C family were synthesized by heat treating iron salts or other iron-containing compounds with zinc-based zeolitic imidazolate frameworks (ZIFs) and/or phenanthroline (as carbon and nitrogen sources), or by heat treating iron-substituted ZIFs. For this family of PGM-free materials, it has been shown that many synthesis variables, such as the metal and carbon-nitrogen macrocycle content, the heat treatment temperature, atmosphere, and temperature profile all affect the activity and durability of the resulting catalysts.4-7 Optimization of these variables and testing the resulting catalyst properties is not a trivial task, and only a limited portion of the composite composition and temperature space has been explored for this family of catalysts. To accelerate optimization of the synthesis variables to obtain improved ORR activity and stability for the Fe-N-C catalysts, high-throughput synthesis and characterization methods were developed and utilized. An automation platform, a multi-port ball-mill, and parallel fixed bed reactors in Argonne’s High-throughput Research Laboratory were used to rapidly synthesize the PGM-free catalysts with systematically-varied synthesis conditions. A multi-channel flow double electrode (m-CFDE) cell and other cells were designed and constructed for the simultaneous testing the ORR activity and stability of the multiple catalysts synthesized. The ORR activity and stability of the catalysts were correlated with their Fe speciation, as determined using Fe K-edge X-ray absorption spectroscopy (XAFS), electrochemically-determined surface areas, and other variables, which is beneficial for the further improved catalyst activity and stability. References B. Pivovar, Nature Catalysis, 2 (2019) 562. S. Thompson and D. Papageorgopoulos, Nature Catalysis, 2 (2019) 558. L. Osmieri, J. Park, D.A. Cullen, P. Zelenay, D.J. Myers, and K.C. Neyerlin, Curr. Opin. Electrochem., 25 (2021) 100627. X. Wang, H. Zhang, H. Lin, S. Gupta, C. Wang, Z. Tao, H. Fu, T. Wang, J. Zheng, G. Wu, and X. Li, Nano Energy, 25 (2016) 110. H. Zhang, S. Hwang, M. Wang, Z. Feng, S. Karakalos, L. Luo, Z. Qiao, X. Xie, C. Wang, D. Su, Y. Shao, and G. Wu, J. Am. Chem. Soc., 139 (2017) 14143-14149. E. Proietti, F. Jaouen, M. Lefevre, N. Larouche, J. Tian, J. Herranz, and J.-P. Dodelet, Nature Comm. 2 (2011) 1. A. Zitolo, V. Goellner, V. Armel, M.-T. Sougrati, T. Mineva, L. Stievano, E. Fonda, and F. Jaouen, Nature Materials, 14 (2015) 937. This work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat). This work utilized the resources of the Advanced Photon Source, a U.S. DOE Office of Science user facility operated by Argonne National Laboratory for DOE Office and was authored by Argonne, a U.S. Department of Energy (DOE) Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.
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Osmieri, Luigi, Tanvir Alam Arman, Guanxiong Wang, Hao Wang, Kenneth C. Neyerlin, Siddharth Komini Babu, and Jacob S. Spendelow. "Electrochemical Diagnostics and Innovative Electrode Architectures to Investigate and Improve Mass Transport in Platinum Group Metal-Free Catalyst Layers." ECS Meeting Abstracts MA2022-02, no. 39 (October 9, 2022): 1424. http://dx.doi.org/10.1149/ma2022-02391424mtgabs.
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To efficiently and extensively utilize hydrogen for transportation and stationary power generation, the development of low-cost and efficient proton exchange membrane fuel cells (PEMFC) is essential.1 Platinum (Pt) is used as catalyst in PEMFC due to its high performance, but its high cost has been one of the major barriers to the extensive use of PEMFC systems for transportation. In particular, high loadings of Pt are required at the PEMFC cathode due to the sluggish kinetics of the oxygen reduction reaction (ORR).2 One of the strategies adopted to overcome this barrier, is the development of low-cost platinum group metal (PGM)-free catalysts.3 Both the ORR activity and durability of PGM-free catalysts has improved considerably in recent years,4 but the mass activity of these materials remains much lower compared to Pt-based catalysts, requiring the use of higher catalyst loadings on the electrode. As a direct consequence, typical PGM-free catalyst layers (CL) are about 1 order of magnitude thicker than Pt-based ones (~100 µm vs. ~10 µm), creating more challenging conditions for transport of O2 and H+ to the active sites and removal of liquid water within the CL.5 A series of in-situ electrochemical diagnostics methods to measure the mass transport resistance in PGM-fee CLs based on H2 and O2 limiting currents have been developed within the DOE-sponsored ElectroCat consortium.4,6 We will show the application of these methods, in conjunction to other well-established in-situ and ex-situ characterizations (cyclic voltammetry, impedance spectroscopy, SEM, X-ray tomography), to explain the performance trend observed in different PGM-free CLs. We examined the impact of different CL fabrication variables like the ionomer-to-catalyst (I/C) ratio, the ink solvent composition, and the ionomer equivalent weight (EW), evidencing the ones providing harsher conditions for mass transport. The results show the importance achieving optimal transport conditions by selecting a proper combination of these fabrication parameters.7,8 With the aim of improving mass transport and ionic conductivity and expanding the CL operational robustness over a broader range of operating conditions, we developed an innovative electrode architecture having differentiated and ordered domains.9 In particular, we designed a CL divided into alternated catalyst and void domains (grooves). We investigated the fabrication of the groovy CL using different methods and tested the performance under different relative humidity conditions. The results show how the groovy CL structure provides performance enhancements compared to a traditional planar CL in conditions more challenging for mass transport, e.g., at high relative humidity and for electrodes prepared with high I/C and low EW ionomer. In addition, we demonstrated that filling the grooves with a material more hydrophobic than the main catalyst domain (e.g., catalyst mixed with ionomer with high EW and low I/C, or carbon mixed with PTFE) we can largely expand the operational robustness in oversaturated conditions. References D. A. Cullen et al., Nat. Energy (2021). D. Banham et al., Sci. Adv., 4, 1–7 (2018). L. Osmieri et al., Curr. Opin. Electrochem., 25, 100627 (2020). P. Zelenay and D. J. Myers, DOE Annual Merit Review - ElectroCat 2.0 (Electrocatalysis Consortium) (2021). L. Osmieri and Q. Meyer, Curr. Opin. Electrochem., 31, 100847 (2021). A. G. Star, G. Wang, S. Medina, S. Pylypenko, and K. C. Neyerlin, J. Power Sources, 450, 227655 (2020). L. Osmieri et al., Nano Energy, 75, 104943 (2020). G. Wang, L. Osmieri, A. G. Star, J. Pfeilsticker, and K. C. Neyerlin, J. Electrochem. Soc., 167, 044519 (2020). J. S. Spendelow, DOE Annual Merit Review - Accessible PGM-free Catalysts and Electrodes (2021).
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Chung, Hoon T., Hanguang Zhang, Jaehyung Park, David A. Cullen, Karren L. More, Deborah J. Myers, Esen E. Alp, and Piotr Zelenay. "Fuel Cell Durability Study of PGM-Free ORR Catalysts." ECS Meeting Abstracts MA2020-01, no. 38 (May 1, 2020): 1680. http://dx.doi.org/10.1149/ma2020-01381680mtgabs.
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Liu, Di-Jia. "(Invited) Understanding the Electrocatalytic Mechanisms of Oxygen and Carbon Dioxide Reduction Reactions." ECS Meeting Abstracts MA2022-01, no. 35 (July 7, 2022): 1468. http://dx.doi.org/10.1149/ma2022-01351468mtgabs.
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Oxygen reduction reaction (ORR) is one of the most important reactions in the field of electrocatalysis today. ORR represents a key cathodic reaction in hydrogen fuel cell, which typically needs to be promoted by the platinum group metals (PGMs), particularly Pt. The high cost of Pt adds significant barrier to the widespread implementation of the fuel cell technology. During the last two decades, substantially amount of effort has been invested in searching for low-cost replacements, or PGM-free catalysts for ORR. Although significant progress has been made, such catalysts still face major challenge in durability. By adding small amount of Pt over PGM-free catalytic substrate, we have found that both activity and stability will be significantly improved through synergistic interaction. [1] To better define synergistic effect in ORR catalysis, however, requires a carefully designed experiment that can separates multiple factors during the catalyst synthesis that can potentially influence the overall activity. In this report, we will discuss our recent study in understanding of the ORR catalysis synergy between Pt/PGM-free components in rationally designed catalyst systems. Another fast developing area of electrocatalysis is CO2 reduction reaction (CO2RR), which promises to electrochemically convert CO2 to fuels and chemicals using renewable electricity. While CO2RR via 2-electron transfer, such as the conversion to CO or formate, has been proven high selective with fast kinetics, conversions to C2+ chemicals require significantly stronger binding between the catalytic site and CO2 to complete multiple electron transfers (8 to 16) and C-C bond coupling steps, therefore are more challenging. More recently, we develop a new amalgamated lithium metal (ALM) synthesis method to preparing highly selective and active CO2RR catalyst for C2+ chemicals such as ethanol production. [2] In this presentation, we will discuss the hypothesis driven CO2RR catalyst design, combined with the mechanistic study for preparing effective catalysts. We will also share some critical insight on CO2RR mechanism through advanced structural characterization and computational modelling. Acknowledgement: This work is supported by U. S. Department of Energy, Hydrogen and Fuel Cell Technologies Office through Office of Energy Efficiency and Renewable Energy and by Office of Science, U.S. Department of Energy under Contract DE-AC02-06CH11357. [1] L. Chong, J. Wen, J. Kubal, F. G. Sen, J. Zou, J. Greeley, M. Chan, H. Barkholtz, W. Ding, and D.-J. Liu, “Ultralow-loading Platinum-Cobalt Fuel Cell Catalysts Derived from Imidazolate Frameworks,” Science (2018) 362, 1276 [2] “Highly selective electrocatalytic CO2 reduction to ethanol by metallic clusters dynamically formed from atomically dispersed copper” Haiping Xu, Dominic Rebollar, Haiying He, Lina Chong, Yuzi Liu, Cong Liu, Cheng-Jun Sun, Tao Li, John V. Muntean, Randall E. Winans, Di-Jia Liu and Tao Xu, (2020) Nature Energy, 5, 623–632
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Ueda, Kakuya, Cheen Aik Ang, Yoshihiro Ito, Junya Ohyama, and Atsushi Satsuma. "NiFe2O4 as an active component of a platinum group metal-free automotive three-way catalyst." Catalysis Science & Technology 6, no. 15 (2016): 5797–800. http://dx.doi.org/10.1039/c6cy00795c.
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To develop a platinum group metal (PGM)-free automotive three-way catalyst (TWC), we investigated the structure–activity relationship for Fe–Ni oxide catalysts and found NiFe2O4 with a spinel structure is an active component of the three-way catalytic reaction (NO–C3H6–CO–O2).
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Adabi Firouzjaie, Horie, Abolfazl Shakouri, Christopher Williams, John R. Regalbuto, and William Earl Mustain. "Highly Efficient Multi-Atom Pt and PtRu Catalysts for Anion Exchange Membrane Fuel Cells." ECS Meeting Abstracts MA2022-01, no. 45 (July 7, 2022): 1895. http://dx.doi.org/10.1149/ma2022-01451895mtgabs.
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During the last decade, anion exchange membrane fuel cells (AEMFCs) have gained popularity due to their promise to provide low cost, high efficiency, high power density, and zero-emissions. Recent years have seen a significant increase in the achievable peak power density and lifetime of AEMFCs, though that performance has come with high loadings of Pt and PtRu catalysts at the cathode and anode, respectively1,2 . However, to displace incumbent proton exchange membrane fuel cells (PEMFCs), AEMFCs must be able to offer much lower cost3,4. Therefore, the U.S. Department of Energy (DOE) recently set some challenging activity targets for AEMFCs5; including a near-term target platinum group metal (PGM) loading of 0.2 mg/cm2 by 2023, 0.125 mg/cm2 by 2024 and zero PGM by 2030. Recently, various efforts have sought to reduce the PGM loading in operating AEMFCs. Some efforts have focused on developing completely PGM-free catalysts, such as Fe-N-C at the cathode6 . However, the nearterm DOE targets can be met by reducing the loading of existing catalysts, which can be accomplished by maximizing metal utilization7. One effective strategy is to improve the mass activity of Pt by increasing the number of active sites through catalyst size or structure control or improving the intrinsic activity of Pt through the manipulation of its electronic structure. One approach that can be used to reduce the PGM loading is to create atomically-dispersed catalysts. This can include single atoms or small multi-atom clusters 8,9 . Therefore, in this work, Pt/C, Pt/NC, PtRu/C and PtRu/NC were fabricated using a simple, and scalable Switch Solvent Synthesis (SWISS) method. This method synthesizes a high density of multi-atom catalysts. It is able to do so by limiting the amount of water that is hydrating the synthesis precursors, which allows for agglomeration to be limited. The catalysts were physically characterized using a wide array of techniques including x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution Cs aberration-corrected scanning transmission electron microscopy (STEM). The catalysts were also tested for their oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) activity in a rotating disk electrode setup. Their in-situ behavior was also investigated operating AEMFCs. With this new generation of low-PGM materials, it was possible to reduce the PGM loading by factor of 12 while achieving comparable performance to commercial catalysts. Also, to assemble a cell with ultralow PGM loading, our previously developed Fe–N–C cathodes6 were paired with a low-loading PtRu/NC anodes (0.05 mg PtRu per cm2, 0.08 mg Pt per cm2), which allowed for the demonstration of a specific power of 25 W per mg PGM (40 W per mg Pt).
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He, Yanghua, Sooyeon Hwang, David A. Cullen, M. Aman Uddin, Lisa Langhorst, Boyang Li, Stavros Karakalos, et al. "Highly active atomically dispersed CoN4 fuel cell cathode catalysts derived from surfactant-assisted MOFs: carbon-shell confinement strategy." Energy & Environmental Science 12, no. 1 (2019): 250–60. http://dx.doi.org/10.1039/c8ee02694g.
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Primbs, Mathias, Yanyan Sun, Aaron Roy, Daniel Malko, Asad Mehmood, Moulay-Tahar Sougrati, Pierre-Yves Blanchard, et al. "Establishing reactivity descriptors for platinum group metal (PGM)-free Fe–N–C catalysts for PEM fuel cells." Energy & Environmental Science 13, no. 8 (2020): 2480–500. http://dx.doi.org/10.1039/d0ee01013h.
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Chong, Lina, Jianguo Wen, Joseph Kubal, Fatih G. Sen, Jianxin Zou, Jeffery Greeley, Maria Chan, Heather Barkholtz, Wenjiang Ding, and Di-Jia Liu. "Ultralow-loading platinum-cobalt fuel cell catalysts derived from imidazolate frameworks." Science 362, no. 6420 (November 8, 2018): 1276–81. http://dx.doi.org/10.1126/science.aau0630.
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Achieving high catalytic performance with the lowest possible amount of platinum is critical for fuel cell cost reduction. Here we describe a method of preparing highly active yet stable electrocatalysts containing ultralow-loading platinum content by using cobalt or bimetallic cobalt and zinc zeolitic imidazolate frameworks as precursors. Synergistic catalysis between strained platinum-cobalt core-shell nanoparticles over a platinum-group metal (PGM)–free catalytic substrate led to excellent fuel cell performance under 1 atmosphere of O2 or air at both high-voltage and high-current domains. Two catalysts achieved oxygen reduction reaction (ORR) mass activities of 1.08 amperes per milligram of platinum (A mgPt−1) and 1.77 A mgPt−1 and retained 64% and 15% of initial values after 30,000 voltage cycles in a fuel cell. Computational modeling reveals that the interaction between platinum-cobalt nanoparticles and PGM-free sites improves ORR activity and durability.
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Barkholtz, Heather M., and Di-Jia Liu. "Advancements in rationally designed PGM-free fuel cell catalysts derived from metal–organic frameworks." Materials Horizons 4, no. 1 (2017): 20–37. http://dx.doi.org/10.1039/c6mh00344c.
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Stariha, Sarah, Kateryna Artyushkova, Michael J. Workman, Alexey Serov, Sam Mckinney, Barr Halevi, and Plamen Atanassov. "PGM-free Fe-N-C catalysts for oxygen reduction reaction: Catalyst layer design." Journal of Power Sources 326 (September 2016): 43–49. http://dx.doi.org/10.1016/j.jpowsour.2016.06.098.
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Liu, Di-Jia. "(Invited) On the Structural and Mechanistic Studies of PGM-Free Oer Catalysts for PEM Electrolyzer." ECS Meeting Abstracts MA2022-01, no. 39 (July 7, 2022): 1755. http://dx.doi.org/10.1149/ma2022-01391755mtgabs.
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Low temperature water electrolysis represents a critical technology for green hydrogen production. Low temperature electrolysis can be operated using either proton exchange or alkaline membrane electrolyte. Compared to alkaline electrolyzer, proton exchange membrane (PEM) electrolyzer offers advantages of significantly higher current density and higher H2 purity, rendering it a preferred technology when high energy efficiency and low footprint are essential. Working in the oxidative and acidic environment under high polarization voltage, however, adds substantial demand to the electrode catalyst and the support. This is particularly the case at anode where the oxygen evolution reaction (OER) takes place. At present, the PGM materials such as Ir black or Ir oxide are catalysts of choice. Their high cost and limited reserve, however, adds a significant cost to PEM electrolyzer, which contributes to the overall expense of hydrogen production next only to the cost of electricity. Replacing Ir with earth-abundant transition metal oxides could help to reduce the electrolyzer system cost. These materials are known to be applicable in the alkaline electrolyte but not in acid due to dissolution. Since the traditional porous carbon cannot be used as the support under the oxidative potential during OER, their stand-alone conductivity represents another critical consideration. Argonne National Laboratory has recently designed and prepared a new class of PGM-free OER catalyst for PEM electrolyzer. The new catalysts are consisted of highly porous yet stable transition metal oxide derived from the metal-organic-frameworks (MOFs). Two catalyst series, ANL-Cat-A and ANL-Cat-B, were developed and investigated. The OER catalyst activity and durability were first measured by rotating disk electrode (RDE) method and in half-cell in the acidic media. Very promising OER activities were achieved. The catalyst durability was also measured through the multiple potential cycling from the voltage of 1.2 V to 2.0 V (vs. RHE) in the acidic electrolyte. Both ANL catalysts demonstrated promising activity and durability in the acidic medium. These PGM-free OER catalysts were also integrated into the membrane electrode assemblies and tested in PEM water electrolyzer under operating condition (60 °C to 80 °C and ambient pressure). Several MEAs demonstrated promising OER current density of 2000 mA/cm2 at 2.2 V iR-corrected . Extensive structural characterizations were carried out, both in static state and under the reaction condition using various tools such as high resolution electron microscopy and in situ X-ray absorption spectroscopy. Interesting correlation between the structure and property relationship was found. Computational modeling was also performed to understand the fundamental mechanism behind electron conductivity and the acid tolerance behind this new class of OER catalysts. Acknowledgement: This work is supported by U. S. Department of Energy, Hydrogen and Fuel Cell Technologies Office through Office of Energy Efficiency and Renewable Energy and by Office of Science, U.S. Department of Energy under Contract DE-AC02-06CH11357.
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Wang, Qianqian, and Liping Ma. "NO oxidative activity of mesoporous LaMnO3 and LaCoO3 perovskite nanoparticles by facile molten-salt synthesis." New Journal of Chemistry 43, no. 7 (2019): 2974–80. http://dx.doi.org/10.1039/c8nj04590a.
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Osmieri, Luigi. "Transition Metal–Nitrogen–Carbon (M–N–C) Catalysts for Oxygen Reduction Reaction. Insights on Synthesis and Performance in Polymer Electrolyte Fuel Cells." ChemEngineering 3, no. 1 (February 11, 2019): 16. http://dx.doi.org/10.3390/chemengineering3010016.
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Platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) have attracted increasing interest as potential candidates to replace Pt, in the view of a future widespread commercialization of polymer electrolyte fuel cell (PEFC) devices, especially for automotive applications. Among different types of PGM-free catalysts, M–N–C materials appear to be the most promising ones in terms of activity. These catalysts can be produced using a wide variety of precursors containing C, N, and one (or more) active transition metal (mostly Fe or Co). The catalysts synthesis methods can be very different, even though they usually involve at least one pyrolysis step. In this review, five different synthesis methods are proposed, and described in detail. Several catalysts, produced approximately in the last decade, were analyzed in terms of performance in rotating disc electrode (RDE), and in H2/O2 or H2/air PEFC. The catalysts are subdivided in five different categories corresponding to the five synthesis methods described, and the RDE and PEFC performance is put in relation with the synthesis method.
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Jiang, Qiongqiong, Yunfei Gao, Vasudev Pralhad Haribal, He Qi, Xingbo Liu, Hui Hong, Hongguang Jin, and Fanxing Li. "Mixed conductive composites for ‘Low-Temperature’ thermo-chemical CO2 splitting and syngas generation." Journal of Materials Chemistry A 8, no. 26 (2020): 13173–82. http://dx.doi.org/10.1039/d0ta03232h.
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Peng, Xiong, Varchaswal Kashyap, Benjamin Ng, Sreekumar Kurungot, Lianqin Wang, John Varcoe, and William Mustain. "High-Performing PGM-Free AEMFC Cathodes from Carbon-Supported Cobalt Ferrite Nanoparticles." Catalysts 9, no. 3 (March 15, 2019): 264. http://dx.doi.org/10.3390/catal9030264.
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Efficient and durable non-precious metal electrocatalysts for the oxygen reduction reaction (ORR) are highly desirable for several electrochemical devices, including anion exchange membrane fuel cells (AEMFCs). Here, cobalt ferrite (CF) nanoparticles supported on Vulcan XC-72 carbon (CF-VC) were created through a facile, scalable solvothermal method. The nano-sized CF particles were spherical with a narrow particle size distribution. The CF-VC catalyst showed good ORR activity, possessing a half-wave potential of 0.71 V. Although the intrinsic activity of the CF-VC catalyst was not as high as some other platinum group metal (PGM)-free catalysts in the literature, where this catalyst really shined was in operating AEMFCs. When used as the cathode in a single cell 5 cm−2 AEMFC, the CF-VC containing electrode was able to achieve a peak power density of 1350 mW cm−2 (iR-corrected: 1660 mW cm−2) and a mass transport limited current density of more than 4 A cm−2 operating on H2/O2. Operating on H2/Air (CO2-free), the same cathode was able to achieve a peak power density of 670 mW cm−2 (iR-corrected: 730 mW cm−2) and a mass transport limited current density of more than 2 A cm−2. These peak power and achievable current densities are among the highest reported values in the literature to date.
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Myers, Deborah J., Ahmed A. Farghaly, Magali Ferrandon, A. Jeremy Kropf, and David A. Cullen. "Platinum Group Metal-Free Oxygen Evolution Electrocatalysts for Alkaline Water Electrolysis." ECS Meeting Abstracts MA2022-02, no. 44 (October 9, 2022): 1672. http://dx.doi.org/10.1149/ma2022-02441672mtgabs.
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The sluggish kinetics of oxygen electrocatalysis and the resulting high overpotentials necessary to achieve useful current densities limit the development of promising technologies, such as fuel cells, water, and carbon dioxide electrolyzers, and metal-oxygen batteries.1 The best catalysts for both the oxygen reduction and oxygen evolution reactions (ORR and OER, respectively) are based on precious, platinum group metals (PGMs), such as platinum and iridium, leading to limitations in the cost-effective implementation of these technologies.2,3 The development of alternative catalysts, with comparable or higher activity and durability to the PGM catalysts and derived from earth-abundant materials has thus been an active research area for decades. Incredible progress has been made in developing PGM-free electrocatalysts for the OER in alkaline environments, with perovskite oxides showing activities comparable to PGM-based catalysts.4,5 Perovskite oxides are a very broad class of materials with the general formula of ABO3, where the B site is occupied by smaller transition metal ions and the A site by larger cations which have 12-fold coordination with O.4 Both the A sites and B sites can be occupied by multiple metal ions, leading to an even more expansive design space for this class of materials. Another interesting class of catalysts is Fe and Ni oxides derived from the electrochemical oxidation of metal-organic frameworks (MOFs), with the advantages of this material over the perovskites being high electronic conductivity and high surface area. This presentation will describe the development and application of a high-throughput methodology to accelerate the exploration of the effects of composition and synthesis parameters on the activity of perovskite oxide and metal-organic framework-derived alkaline electrolyte OER catalysts. The evolution of the oxidation state and atomic structure of the MOF materials in the electrochemical environment, as determined using in situ X-ray absorption spectroscopy (XAS), as well as the evolution of the morphology of the catalyst, as determined using electron microscopy, will be described. References Yang, X. Han, A.I. Douka, L. Huang, L. Gong, C. Xia, H.S. Park, and B.Y. Xia, Adv. Func. Mater., 31 (2021) 2007602. Pivovar, Nature Catalysis, 2 (2019) 562. Thompson and D. Papageorgopoulos, Nature Catalysis, 2 (2019) 558. Hwang, R.R. Rao, L. Giordano, Y. Katayama, Y. Yu, and Y. Shao-Horn, Science 358 (2017) 751. Suntivich, K.J. May, H.A. Gasteiger, J.B. Goodenough, Y. Shao-Horn, Science, 334 (2011) 1383. Acknowledgements This work was supported by the U.S. Department of Energy (DOE), Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office (HFTO) under the auspices of the Electrocatalysis Consortium (ElectroCat 2.0). This work was also supported by DOE, Advanced Research Projects Agency-Energy (ARPA-E) under the DIFFERENTIATE program. This work utilized the resources of the Advanced Photon Source, a DOE Office of Science user facility operated by Argonne National Laboratory for DOE Office and was authored by Argonne, a DOE Office of Science laboratory operated for DOE by UChicago Argonne, LLC under contract no. DE-AC02-06CH11357.
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Banham, Dustin, Ja‐Yeon Choi, Takeaki Kishimoto, and Siyu Ye. "Integrating PGM‐Free Catalysts into Catalyst Layers and Proton Exchange Membrane Fuel Cell Devices." Advanced Materials 31, no. 31 (January 3, 2019): 1804846. http://dx.doi.org/10.1002/adma.201804846.
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Strasser, Derek James, Max Pupucevski, Natalia Macauley, Judith Lattimer, Sichen Zhong, and Hui Xu. "(Invited) Progress and Perspective Towards Low-Cost High-Performance Anion Exchange Membrane Water Electrolysis." ECS Meeting Abstracts MA2022-02, no. 44 (October 9, 2022): 1675. http://dx.doi.org/10.1149/ma2022-02441675mtgabs.
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Hydrogen is at the forefront of clean energy use and storage in the goal to drastically reduce anthropogenic carbon dioxide and combat global climate change. However, hydrogen production to-date is accomplished via steam methane reforming which, for every ton of hydrogen produced 5.5 tons of CO2 is liberated. One viable technical solution for production of clean hydrogen is water electrolysis. To this end DOE has implemented the Hydrogen Earthshot initiative to cleanly produce hydrogen at 2 $/kg by 2025 and 1 $/kg by 2030. Of the several commercial water electrolysis technologies available, proton exchange membrane water electrolysis (PEMWE) currently offers the most benefits including operations at low temperature, differential pressure, and high current density (≥3 A/cm2). Commercialization of PEMWE has advanced rapidly despite several significant disadvantages which include the necessity of scarce expensive platinum-group metal (PGM) catalysts, expensive perfluorinated membranes, and significant environmental impacts of perfluorinated alkyl substances (PFAS) used in membrane production. The solution to these challenges is the development of alkaline exchange membrane water electrolysis (AEMWE) which retains the advantageous characteristics of PEMWE without the need for PGM catalysts or perfluorinated membranes. Here in, we report on our current progress of AEMWEs, which covers PGM-free catalyst development, low-cost and durable AEM development and electrode design development. From a commercial point of view, given a high-performance durable membrane, manufacturing MEAs is a critical next step toward commercialization. Therefore, development of an AEM with accessible thermal transitions prior to the onset of quaternary ammonium degradation is key to enabling proven MEA fabrication techniques such as hot-pressing and decal transfer of electrodes. Through a novel synthetic approach, we will describe the preparation of functionalized copolymers and terpolymers containing latent cross-linking functionality. Ultimately, we will demonstrate the manufacturability of MEAs from our PGM-free catalysts and membrane materials employing hot-pressing and decal transfer of electrodes along with single cell evaluations. We will also discuss factors that affect the degradation of AEMWEs and solutions to address these challenges.
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Maxwell, Derrick, Ian Kendrick, and Sanjeev Mukerjee. "(Digital Presentation) Interfacial Durability of Anion Exchange Membrane Water Electrolyzers (AEMWEs)." ECS Meeting Abstracts MA2022-02, no. 44 (October 9, 2022): 1685. http://dx.doi.org/10.1149/ma2022-02441685mtgabs.
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There is a growing industrial appeal of anion exchange membrane water electrolyzers (AEMWEs) to produce hydrogen. This is spurred by the recent advancements in high current density operation capability with relatively low overvoltage performance. Cost reduction has been pursued by reducing the reliance on expensive platinum group metal (PGM) catalysts while still achieving long-term, continuous operation conditions most relevant to the industry: high current densities above 2 A/cm2 while retaining overvoltage performance so that overall cell potential is less than 2V. Along with a selection of appropriate PGM-free catalysts, other approaches exist that drive down the associated cost to produce hydrogen from water splitting. Sources of water are extended to brackish and even seawater to further drive down costs due to the removal of costly water purification requirements. The introduction of salt to the water source may improve overvoltage performance in an AEMWE by raising electrolyte conductivity, however, it may also lead to some unknown instability within more severe high current operating conditions. The challenge remains that AEMWE durability testing is not standardized, and more minute interfacial degradation mechanisms between ionomer, catalyst, membrane, and electrolyte are not well characterized for many industrially relevant materials. When approaching AEMWE performance improvements with PGM-free and variable electrolyte content in water solution sources, the long-term performance needs to be demonstrated in a stable and reliable manner. A series of in-situ Raman experiments are presented in coordination with ex-situ spectroscopic and physical analysis of components in PGM-free AEMWEs that are expected to contribute to overall degradation of electrolyzer performance. Interfacial durability improvements are sought by providing insight into the main sources of failure during high current and long-term operations. Electrochemical testing protocols are also developed and presented in order to seek standardization of testing procedures. In-line gas chromatography (GC) analysis is also presented in tandem with other analytical methods to confirm product gas purity and corroborate hypotheses on possible degradation mechanisms.
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Osmieri, Luigi, and Piotr Zelenay. "(Invited) Towards Entirely Platinum Group Metal-Free Water Electrolyzers: Innovative Electrocatalysts for Oxygen Evolution and Hydrogen Evolution Reactions." ECS Meeting Abstracts MA2022-01, no. 34 (July 7, 2022): 1379. http://dx.doi.org/10.1149/ma2022-01341379mtgabs.
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Making the production of “green” hydrogen (H2) cost-effective requires the development of high-performance and affordable low-temperature water electrolyzers (LTWE).1 Currently, the most mature technology for H2 production using renewable electricity is the liquid alkaline electrolysis (AE). This technology suffers several major drawbacks such as gas crossover, relatively low current density, and the use of highly corrosive concentrated alkaline solutions (20-40% KOH). Proton exchange membrane (PEM) electrolysis, a valid alternative to AE technology, already commercialized on a large scale, enables operation on pure water thus eliminating corrosion, reducing gas crossover and allowing higher current density. However, the main drawback of PEM electrolyzers is the need of very expensive and rare platinum group metals (PGMs) such as Ir and Pt as catalysts for oxygen evolution reaction (OER) at the anode and hydrogen evolution reaction (HER) at the cathode, respectively.2 Recent advancements in performance and stability of anion exchange membranes (AEMs) have enabled a new type of alkaline membrane-based LTWE operating on pure water and with PGM-free catalysts.3,4 If successful, this new AEM-LTWE technology will allow to overcome the drawbacks of AEs and PEM-LTWEs while benefiting from their respective advantages in a major breakthrough in the production of “green” H2 at a low cost. In this scenario crucial is the development of high-performance PGM-free electrocatalysts for both OER and HER. Due to the operation at high potentials, carbon-based catalysts and supports cannot be used at the anode. Therefore, the most common PGM-free anode catalysts are based on transition metal oxides, which suffer, however, from low surface area and electronic conductivity, limiting the electrocatalytic performance.5,6 The catalysts with the most promising OER activity in alkaline environment are Ni-based alloys, oxides, and (oxy)hydroxides.7 The combination of Ni with other first-row transition metals such as Fe and Co was found to increase the OER catalytic activity.8,9 In this work, we present a new method for synthesizing NiFe OER catalysts. The catalyst was synthesized via a sol-gel method, followed by a thermal treatment. The impact on the OER activity in alkaline liquid electrolyte of different synthesis parameters such as the Ni-to-Fe atomic ratio, the addition of a third transition metal (e.g., Co, Mn), the thermal treatment temperature and atmosphere were investigated. Then, the most promising electrocatalysts were tested in an AEM-LTWE operating with pure water and supporting electrolyte solution. Bimetallic HER PGM-free catalysts were also developed by combining one a first-row transition metal, e.g. Ni, with a second-row transition metal, e.g. Mo. These HER catalysts were synthesized by either (i) using the sol-gel approach described above or (ii) via a metal organic framework (MOF) method similar to the one used in the synthesis of “atomically dispersed” M-N-C catalysts for oxygen reduction reaction.10 References A. M. Oliveira, R. R. Beswick, and Y. Yan, Curr. Opin. Chem. Eng., 33, 100701 (2021). H. A. Miller et al., Sustain. Energy Fuels, 4, 2114–2133 (2020). J. Xiao et al., ACS Catal., 11, 264–270 (2021). D. Li et al., Nat. Energy, 5, 378–385 (2020). Q. Gao et al., Chem. Eng. J., 331, 185–193 (2018). D. Xu et al., ACS Catal., 9, 7–15 (2019). S. Fu et al., Nano Energy, 44, 319–326 (2018). G. Zhang et al., Appl. Catal. B Environ., 286, 119902 (2021). P. Chen and X. Hu, Adv. Energy Mater., 10, 1–6 (2020). Y. He et al., Energy Environ. Sci., 12, 250–260 (2019).
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Osmieri, Luigi, Tanvir Alam Arman, Siddharth Komini Babu, and Jacob S. Spendelow. "Grooved Electrodes to Enhance Mass Transport in Thick Platinum Group Metal-Free Fuel Cell Cathodes." ECS Meeting Abstracts MA2022-01, no. 35 (July 7, 2022): 1459. http://dx.doi.org/10.1149/ma2022-01351459mtgabs.
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Producing “green” hydrogen at a low cost is one of the main strategies adopted by several countries to reduce their greenhouse gas emissions.1 To enable the hydrogen utilization for transportation and stationary power generation, developing low-cost and efficient proton exchange membrane fuel cells (PEMFC) is essential.2 To date, platinum (Pt) is used as the preferred catalyst in PEMFCs due to its high catalytic activity for both hydrogen oxidation and oxygen reduction reaction (ORR).3 Due to high cost and scarcity of Pt, research has extensively focused on developing low-cost platinum group metal (PGM)-free electrocatalysts for ORR, with impressive performance improvements recently achieved.4,5 However, the lower mass activity of PGM-free catalysts compared to Pt requires much higher loadings in the cathode, resulting in ca. 10 times thicker catalyst layers (i.e., ~100 vs. ~10 µm), with consequent negative impact on mass transport.6 In the fuel cell group at Los Alamos National Laboratory, a series of structured electrodes with differentiated and ordered segments have been developed, enabling a faster transport of ORR reactants (O2, H+) and products (H2O).7 To enhance the O2 gas transport towards the active sites and improve the catalyst utilization, we developed an electrode structure with alternated catalyst and void (or grooves) domains, aiming to improve the electrodes operational robustness. The grooved structure provides a more direct and less tortuous path for O2 diffusion within the catalyst layer, enabling at the same time a faster removal of the liquid H2O. Using a commercial Fe-N-C PGM-free catalyst, we fabricated a series of grooved electrodes and corresponding flat electrodes with the same catalyst loading and ink composition. From tests under different relative humidity (RH) conditions, we found that the grooved electrodes outperform the flat baseline electrodes at high RH and in oversaturated conditions, where the mass transport is more hindered by the massive presence of liquid water and ionomer swelling.8,9 The grooves improved the O2 mass transport by facilitating a fast removal of the liquid water, without negatively affecting the H+ conductivity. In addition, we showed that filling the grooves with a hydrophobic carbon-based material further improved the water removal from the catalyst layer, increasing the performance at high RH. References A. M. Oliveira, R. R. Beswick, and Y. Yan, Curr. Opin. Chem. Eng., 33, 100701 (2021). D. A. Cullen et al., Nat. Energy (2021). D. Banham et al., Sci. Adv., 4, 1–7 (2018). H. Zhang et al., Energy Environ. Sci., 12, 2548–2558 (2019). A. Uddin et al., ACS Appl. Mater. Interfaces, 12, 2216–2224 (2020). L. Osmieri and Q. Meyer, Curr. Opin. Electrochem., 31, 100847 (2021). J. S. Spendelow, DOE Annual Merit Review - Accessible PGM-free Catalysts and Electrodes (2021). A. Kusoglu, T. J. Dursch, and A. Z. Weber, Adv. Funct. Mater., 26, 4961–4975 (2016). G. Wang, L. Osmieri, A. G. Star, J. Pfeilsticker, and K. C. Neyerlin, J. Electrochem. Soc., 167, 044519 (2020).
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Beltran, Diana, Yachao Zeng, Gang Wu, Xianglin Li, and Shawn Litster. "Degradation Acceleration-Factor Analysis for Platinum Group Metal (PGM)-Free Polymer Electrolyte Fuel Cell Cathodes." ECS Meeting Abstracts MA2022-02, no. 42 (October 9, 2022): 1602. http://dx.doi.org/10.1149/ma2022-02421602mtgabs.
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This work explores designs and methods that can mitigate degradation and can be used to expand models to predict PGM-free fuel cell degradation due to voltage cycling during accelerated stress tests (AST) and constant potential holds, specifically current density loss over time. The motivation behind investigating degradation mechanisms is that most of the recent advances have mostly focused on enhancing initial electrocatalytic activity, and not on catalyst stability. Advancements in catalyst stability are less substantial and are well below the level for commercialization. The objective is to determine the impact of the operating point on degradation rate in membrane electrode assemblies (MEAs) and to perform time-efficient evaluation of degradation acceleration factors on a single MEA. The preliminary AST cycling results show that reducing temperature and upper potential cycling limit considerably reduces degradation rates. This work can help identify operating points that optimize between performance and durability using empirical data. Ultimately, the correlations extracted from this work can be applied into drive-cycle models for PGM-free catalysts for simulation-based lifetime performance forecasting. This work was partially supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy under grant DE-0008440 (Prime: University of Kansas).
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Sun, Mingze, Shuyan Gong, Yu-Xiao Zhang, and Zhiqiang Niu. "A perspective on the PGM-free metal–nitrogen–carbon catalysts for PEMFC." Journal of Energy Chemistry 67 (April 2022): 250–54. http://dx.doi.org/10.1016/j.jechem.2021.10.014.
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Yin, Xi, and Piotr Zelenay. "(Invited)Kinetic Models for the Degradation Mechanisms of PGM-Free ORR Catalysts." ECS Transactions 85, no. 13 (June 19, 2018): 1239–50. http://dx.doi.org/10.1149/08513.1239ecst.
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Bevilacqua, Nico, Rohan Rajeev Gokhale, Alexey Serov, Rupak Banerjee, Michael A. Schmid, Plamen Atanassov, and Roswitha Zeis. "Comparing Novel PGM-Free, Platinum, and Alloyed Platinum Catalysts for HT-PEMFCs." ECS Transactions 86, no. 13 (July 23, 2018): 221–29. http://dx.doi.org/10.1149/08613.0221ecst.
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Wan, Xin, Xiaofang Liu, and Jianglan Shui. "Stability of PGM-free fuel cell catalysts: Degradation mechanisms and mitigation strategies." Progress in Natural Science: Materials International 30, no. 6 (December 2020): 721–31. http://dx.doi.org/10.1016/j.pnsc.2020.08.010.
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Zhang, Hanguang, Hannah Osgood, Xiaohong Xie, Yuyan Shao, and Gang Wu. "Engineering nanostructures of PGM-free oxygen-reduction catalysts using metal-organic frameworks." Nano Energy 31 (January 2017): 331–50. http://dx.doi.org/10.1016/j.nanoen.2016.11.033.
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Sgarbi, Ricardo, Huong Doan, and Marian Chatenet. "Carbon-Capped Monometallic and Bimetallic Catalysts for Hydrogen Oxidation Reaction (HOR) and Their Positive Features on Durability in Alkaline Conditions." ECS Meeting Abstracts MA2022-01, no. 45 (July 7, 2022): 1902. http://dx.doi.org/10.1149/ma2022-01451902mtgabs.
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Alkaline fuel cells (AFC) and anion exchange membrane fuel cells (AEMFC) have exhibited attractive advantages versus their acid counterparts, including the strategical possibility of using PGM-free catalysts in the electrode composition.[1,2] PGM-free catalysts remain a challenge regarding the hydrogen oxidation reaction (HOR) catalysis, due to the reduced initial and long-term performance so far.[3,4] PGM-based materials have the highest HOR performances,[5] but Pt- and Pd-based catalysts undergo detrimental metallic nanoparticles detachment from the carbon support and agglomeration (in minor extent) upon extended potential cycling in the alkaline environments.[6,7] In this work, we explore the effect of long-term durability on the nanoparticles wrapped by a carbon layer, labeled here as capped catalysts; two different types of carbon-capped catalysts are evaluated, such as monometallic (PdG2/C) and bimetallic (PdNiG2/C) against their commercial ones (Pd/C and PdNi/C from Premetek). All the catalysts were evaluated in RDE set-up, in couple with IL-TEM, XPS and ICP-MS techniques for before and after accelerated stress test (0.1 – 1.23 V vs. RHE – 3s each potential), up to 6000 cycles. The durability enhancement is achieved when: i) there is a carbon-cap and ii) there is a second metal (i.e. Ni) on the surface of Pd. Thus, in the case of carbon-capped bimetallic (PdNiG2/C), there is a double protection of the Pd nanoparticles (from the carbon-cap and the presence of nickel). In the same time, the HOR activity is high. In the end, the best compromise of durability follows the trend: PdNiG2/C > PdNi/C > PdG2/C > Pd/C. These positive features of the carbon-capped bimetallic material open the way to the design of robust catalysts for highly-durable anodes for alkaline fuel cell systems. [1] D. R. Dekel, J. Power Sources 2018, 375, 158–169. [2] E. Wagner, H. ‐J. Kohnke, Fuel Cells 2020, 1–12. [3] A. G. Oshchepkov, G. Braesch, A. Bonnefont, E. R. Savinova, M. Chatenet, ACS Catal. 2020, 10, 7043–7068. [4] W. E. Mustain, M. Chatenet, M. Page, Y. S. Kim, Energy Environ. Sci. 2020, 13, 2805–2838. [5] W. Sheng, M. Myint, J. G. Chen, Y. Yan, Energy Environ. Sci. 2013, 6, 1509–1512. [6] C. Lafforgue, F. Maillard, V. Martin, L. Dubau, M. Chatenet, ACS Catal. 2019, 9, 5613–5622. [7] A. Zadick, L. Dubau, N. Sergent, G. Berthomé, M. Chatenet, ACS Catal. 2015, 5, 4819–4824.
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Costa de Oliveira, Maida Aysla, Alessandra D’Epifanio, Hitoshi Ohnuki, and Barbara Mecheri. "Platinum Group Metal-Free Catalysts for Oxygen Reduction Reaction: Applications in Microbial Fuel Cells." Catalysts 10, no. 5 (April 26, 2020): 475. http://dx.doi.org/10.3390/catal10050475.
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Scientific and technological innovation is increasingly playing a role for promoting the transition towards a circular economy and sustainable development. Thanks to its dual function of harvesting energy from waste and cleaning up waste from organic pollutants, microbial fuel cells (MFCs) provide a revolutionary answer to the global environmental challenges. Yet, one key factor that limits the implementation of larger scale MFCs is the high cost and low durability of current electrode materials, owing to the use of platinum at the cathode side. To address this issue, the scientific community has devoted its research efforts for identifying innovative and low cost materials and components to assemble lab-scale MFC prototypes, fed with wastewaters of different nature. This review work summarizes the state-of the-art of developing platinum group metal-free (PGM-free) catalysts for applications at the cathode side of MFCs. We address how different catalyst families boost oxygen reduction reaction (ORR) in neutral pH, as result of an interplay between surface chemistry and morphology on the efficiency of ORR active sites. We particularly review the properties, performance, and applicability of metal-free carbon-based materials, molecular catalysts based on metal macrocycles supported on carbon nanostructures, M-N-C catalysts activated via pyrolysis, metal oxide-based catalysts, and enzyme catalysts. We finally discuss recent progress on MFC cathode design, providing a guidance for improving cathode activity and stability under MFC operating conditions.
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Seeberger, Dominik, David McLaughlin, Pascal Hauenstein, and Simon Thiele. "Bipolar-interface fuel cells – an underestimated membrane electrode assembly concept for PGM-free ORR catalysts." Sustainable Energy & Fuels 4, no. 5 (2020): 2508–18. http://dx.doi.org/10.1039/d0se00288g.
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We present the first combination of a bipolar interface fuel cell with a commercial Fe–N/C catalyst as an alkaline cathode and a PGM-based, acidic anode, both separated by a proton exchange membrane (PEM).
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Osmieri, Luigi, Yanghua He, and Piotr Zelenay. "(Invited, Digital Presentation) La-Sr-Co Oxide Catalysts for Oxygen Evolution Reaction in Anion Exchange Membrane Water Electrolyzers: The Role of Electrode Fabrication on Performance and Durability." ECS Meeting Abstracts MA2022-01, no. 39 (July 7, 2022): 1718. http://dx.doi.org/10.1149/ma2022-01391718mtgabs.
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The low temperature water electrolysis technology is essential to allow the production of “green” hydrogen at an affordable cost. Recently, successful development and commercialization of anion exchange membranes (AEMs) with improved performance and durability has accelerated progress in low-temperature water electrolyzers (LTWEs) with AEM acting as a solid polymer electrolyte.1 Although still at an R&D stage, AEM-LTWEs are attracting a lot of interest as a promising alternative to liquid-alkaline and proton exchange membrane (PEM) devices thanks to the promise of operating with pure water feed and using inexpensive platinum group metal-free (PGM-free) electrocatalysts.2 Among different catalysts for oxygen evolution reaction (OER), La-Co perovskite oxides have been extensively investigated in liquid alkaline electrolytes, showing promising OER activity and stability.3–6 A series of La-Sr-Co oxides were recently developed by a joint research effort of Los Alamos National Laboratory and Pajarito Powder LLC, showing promising performance in an AEM-LTWE.7 In this work, we investigated the application of a LaxSr1-xCoO3-δ oxide at the AEM-LTWE anode. As first step, we prepared and tested a series of membrane electrode assemblies (MEA) using different commercial AEMs and ionomers, as well as standard commercial PGM catalysts (PtRu/C on the cathode and IrO2 on the anode). This first set of experiments served to establish a performance baseline and to validate the MEA fabrication method and testing procedure. For testing the LaxSr1-xCoO3-δ PGM-free OER catalyst, we fabricated a series of three electrodes using the same procedure but varying the ink formulation. We demonstrated how the anode catalyst ink composition is improving the AEM-LTWE performance and durability when using a PGM-free catalyst. In particular, we investigated the electrolyzer operation with pure water and with 0.1 M KOH and 1% K2CO3 aqueous electrolyte solutions feed. The electrolyzer performance was much less sensitive to the electrode composition when operated with a supporting electrolyte than when operated on pure water. In the latter case, achieving an optimum interface between the AEM, ionomer, and catalyst particles is essential to ensure good OH- ionic conductivity within the electrode. On the other hand, when a supporting electrolyte solution is used, the abundance of OH- ions within the electrode volume enables a faster ionic OH- transport, making the electrolyzer operation less sensitive to electrode optimization parameters. References H. A. Miller et al., Sustain. Energy Fuels, 4, 2114–2133 (2020). G. A. Lindquist et al., ACS Appl. Mater. Interfaces (2021). C. E. Beall, E. Fabbri, and T. J. Schmidt, ACS Catal., 11, 3094–3114 (2021). J. Suntivich, K. J. May, H. A. Gasteiger, J. B. Goodenough, and Y. Shao-horn, Science (80-. )., 334, 2010–2012 (2011) http://www.sciencemag.org/cgi/doi/10.1126/science.1212858. J. Suntivich et al., Nat. Chem., 3, 546–550 (2011) http://www.nature.com/doifinder/10.1038/nchem.1069. J. Kim, X. Chen, P. C. Shih, and H. Yang, ACS Sustain. Chem. Eng., 5, 10910–10917 (2017). H. T. Chung, 2020 DOE Annu. Merit Rev. - Proj. ID p185 (2020).
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Liu, Di-Jia. "(Invited) ORR, OER and CO2RR – the Promises and Challenges in PGM-Free Catalysts." ECS Meeting Abstracts MA2021-02, no. 42 (October 19, 2021): 1286. http://dx.doi.org/10.1149/ma2021-02421286mtgabs.
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Wu, Gang. "Current challenge and perspective of PGM-free cathode catalysts for PEM fuel cells." Frontiers in Energy 11, no. 3 (June 16, 2017): 286–98. http://dx.doi.org/10.1007/s11708-017-0477-3.
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