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Author: Grafiati
Published: 10 December 2022
Last updated: 9 March 2023

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1

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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2

Jang, Kil Nam, Kwang Seon Han, Ji Sook Hong, Young-Woo You, and Taek Sung Hwang. "Basic Research to Develop PGM-free DeNOx Catalyst for LNT." Clean Technology 21, no. 2 (June 30, 2015): 117–23. http://dx.doi.org/10.7464/ksct.2015.21.2.117.

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3

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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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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5

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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6

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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7

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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8

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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9

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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10

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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11

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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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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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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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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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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Yin, Xi, Edward F. Holby, and Piotr Zelenay. "Comment on “Non-PGM electrocatalysts for PEM fuel cells: effect of fluorination on the activity and stability of a highly active NC_Ar + NH3 catalyst” by Gaixia Zhang, Xiaohua Yang, Marc Dubois, Michael Herraiz, Régis Chenitz, Michel Lefèvre, Mohamed Cherif, François Vidal, Vassili P. Glibin, Shuhui Sun and Jean-Pol Dodelet, Energy Environ. Sci., 2019, 12, 3015–3037, 10.1039/C9EE00867E." Energy & Environmental Science 14, no. 2 (2021): 1029–33. http://dx.doi.org/10.1039/d0ee02069a.

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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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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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20

Peterson, David, Dimitrios Papageorgopoulos, Piotr Zelenay, and Deborah J. Myers. "(Invited) Electrocat 2.0: Accelerating PGM-Free Catalyst and Electrode Development." ECS Meeting Abstracts MA2021-02, no. 44 (October 19, 2021): 1331. http://dx.doi.org/10.1149/ma2021-02441331mtgabs.

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21

Shi, Qiurong, Yanghua He, and Gang Wu. "High‐Performance Direct Methanol Fuel Cells with PGM‐Free Cathode." ECS Meeting Abstracts MA2020-01, no. 38 (May 1, 2020): 1679. http://dx.doi.org/10.1149/ma2020-01381679mtgabs.

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22

Pacella, M., A. Garbujo, J. Fabro, M. Guiotto, Q. Xin, M. M. Natile, P. Canu, P. Cool, and A. Glisenti. "PGM-free CuO/LaCoO3 nanocomposites: New opportunities for TWC application." Applied Catalysis B: Environmental 227 (July 2018): 446–58. http://dx.doi.org/10.1016/j.apcatb.2018.01.053.

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23

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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24

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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25

Roy, Aaron, Morteza R. Talarposhti, Stanley J. Normile, Iryna V. Zenyuk, Vincent De Andrade, Kateryna Artyushkova, Alexey Serov, and Plamen Atanassov. "Nickel–copper supported on a carbon black hydrogen oxidation catalyst integrated into an anion-exchange membrane fuel cell." Sustainable Energy & Fuels 2, no. 10 (2018): 2268–75. http://dx.doi.org/10.1039/c8se00261d.

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This work introduces the first practical platinum group metal-free (PGM-free) electrocatalyst for the hydrogen oxidation reaction (HOR) in alkaline membrane fuel cells (AMFC), based on nickel-rich Ni95Cu5-alloy nanoparticles.
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26

Chander, Monica, Barbara Setlow, and Peter Setlow. "The enzymatic activity of phosphoglycerate mutase from gram-positive endospore-forming bacteria requires Mn2+ and is pH sensitive." Canadian Journal of Microbiology 44, no. 8 (August 1, 1998): 759–67. http://dx.doi.org/10.1139/w98-060.

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The enzymatic activity of phosphoglycerate mutase (Pgm) from three gram-positive endospore-forming bacteria (Bacillus subtilis, Clostridium perfringens, and Sporosarcina ureae) requires Mn2+ and is very sensitive to pH; at low concentrations of Mn2+, a pH change from 8 to 6 resulted in greater than 30- to 200-fold decreases in the activity of these Pgms. However, Pgm deactivation at pH 6 was reversed by shifting the enzyme to pH 7 or 8. Free Mn2+ was not directly involved in Pgm catalysis, although enzyme-bound Mn2+ may be involved. The rate of catalysis by Mn2+-containing Pgm was also slightly pH dependent, although the Km for 3-phosphoglyceric acid appeared to be the same at pH 6, 7, and 8. These findings suggest that Mn2+ binds to catalytically inactive Pgm and converts it to a catalytically competent form, and further, that pH influences the efficiency with which the enzyme binds Mn2+. The extreme pH sensitivity of the Mn2+-dependent Pgms supports a model in which this enzyme is inhibited during sporulation by acidification of the forespore, thus allowing accumulation of the spore's large depot of 3-phospho-glyceric acid. The activity of Pgm from two closely related gram-positive bacteria that do not form spores (Planococcus citreus and Staphylococcus saprophyticus) also requires Mn2+ and is pH sensitive. In contrast, the Pgm activities from two more distantly related non-endospore-forming gram-positive bacteria (Micrococcus luteus and Streptomyces coelicolor) are neither dependent on metal ions nor particularly sensitive to pH.Key words: Bacillus, Clostridium, Mn2+, phosphoglycerate mutase, sporulation.
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27

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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28

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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29

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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30

Olivotos, Spiros, and Maria Economou-Eliopoulos. "Gibbs Free Energy of Formation for Selected Platinum Group Minerals (PGM)." Geosciences 6, no. 1 (January 6, 2016): 2. http://dx.doi.org/10.3390/geosciences6010002.

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31

Anandha Ganesh, P., A. N. Prakrthi, S. Selva Chandrasekaran, and D. Jeyakumar. "Shape-tuned, surface-active and support-free silver oxygen reduction electrocatalyst enabled high performance fully non-PGM alkaline fuel cell." RSC Advances 11, no. 40 (2021): 24872–82. http://dx.doi.org/10.1039/d1ra02718b.

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A fully non-PGM alkaline membrane fuel cell with “highest fuel cell activity” was achieved using a hierarchically shape-tuned, small, surface-active, support-free, worm-shaped nano-structured silver oxygen reduction reaction electro-catalyst.
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32

Toudret, Pierre, Jean-François Blachot, Marie Heitzmann, and Pierre-André Jacques. "Impact of the Cathode Layer Printing Process on the Performance of MEA Integrating PGM Free Catalyst." Catalysts 11, no. 6 (May 24, 2021): 669. http://dx.doi.org/10.3390/catal11060669.

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In this work, platinum group metal (PGM) free-based cathode active layers were prepared using different printing techniques. The membrane electrode assemblies (MEAs) integrate a PGM free catalyst based on Fe, N and C atoms at the cathode side. Scanning electron microscopy (SEM) images of MEA cross sections showed the strong impact of the fabrication process on the cathode structure, the porosity and the ionomer repartition. The MEAs were characterized in a 25 cm2 single cell using cyclic voltammetry under H2/N2. The performance of the MEAs and the double layer capacity of the cathodes were also shown to be linked to the process used. The comparison of the electrochemical accessible surface of the catalyst and of its surface area (SBET) led to the determination of a utilization factor. The coated membrane (CCM) made using the decal transfer process gives the best performances.
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33

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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34

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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35

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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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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37

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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38

Nakayama, Hiroki, Yasuharu Kanno, Makoto Nagata, and Xiaolai Zheng. "Development of TWC and PGM Free Catalyst Combination as Gasoline Exhaust Aftertreatment." SAE International Journal of Engines 9, no. 4 (October 17, 2016): 2194–200. http://dx.doi.org/10.4271/2016-01-2323.

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39

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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40

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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41

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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42

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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43

Thompson, Simon T., Adria R. Wilson, Piotr Zelenay, Deborah J. Myers, Karren L. More, K. C. Neyerlin, and Dimitrios Papageorgopoulos. "ElectroCat: DOE's approach to PGM-free catalyst and electrode R&D." Solid State Ionics 319 (June 2018): 68–76. http://dx.doi.org/10.1016/j.ssi.2018.01.030.

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44

Costa de Oliveira, Maida Aysla, Barbara Mecheri, Alessandra D’Epifanio, Francesca Zurlo, and Silvia Licoccia. "Optimization of PGM-free cathodes for oxygen reduction in microbial fuel cells." Electrochimica Acta 334 (February 2020): 135650. http://dx.doi.org/10.1016/j.electacta.2020.135650.

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45

Gokhale, Rohan, Tristan Asset, Guoqing Qian, Alexey Serov, Kateryna Artyushkova, Brian C. Benicewicz, and Plamen Atanassov. "Implementing PGM-free electrocatalysts in high-temperature polymer electrolyte membrane fuel cells." Electrochemistry Communications 93 (August 2018): 91–94. http://dx.doi.org/10.1016/j.elecom.2018.06.019.

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46

Reshetenko, Tatyana V., Guenter Randolf, Madeleine Odgaard, Barr Zulevi, Alexey Serov, and Andrei Kulikovsky. "Effect of Cathode Proton Conductivity on PGM-free PEM Fuel Cell Performance." ECS Meeting Abstracts MA2020-02, no. 41 (November 23, 2020): 2686. http://dx.doi.org/10.1149/ma2020-02412686mtgabs.

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47

Alipour Moghadam Esfahani, Reza, Fanqi Kong, Keenan Black-Araujo, Levi J. Easton, Iraklii I. Ebralidze, and E. Bradley Easton. "A doped metal oxide PGM-free electrocatalyst for the oxygen reduction reaction." Electrochimica Acta 438 (January 2023): 141564. http://dx.doi.org/10.1016/j.electacta.2022.141564.

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48

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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49

Levander, Fredrik, Ulrika Andersson, and Peter Rådström. "Physiological Role of β-Phosphoglucomutase inLactococcus lactis." Applied and Environmental Microbiology 67, no. 10 (October 1, 2001): 4546–53. http://dx.doi.org/10.1128/aem.67.10.4546-4553.2001.

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ABSTRACT A β-phosphoglucomutase (β-PGM) mutant of Lactococcus lactis subsp. lactis ATCC 19435 was constructed using a minimal integration vector and double-crossover recombination. The mutant and the wild-type strain were grown under controlled conditions with different sugars to elucidate the role of β-PGM in carbohydrate catabolism and anabolism. The mutation did not significantly affect growth, product formation, or cell composition when glucose or lactose was used as the carbon source. With maltose or trehalose as the carbon source the wild-type strain had a maximum specific growth rate of 0.5 h−1, while the deletion of β-PGM resulted in a maximum specific growth rate of 0.05 h−1 on maltose and no growth at all on trehalose. Growth of the mutant strain on maltose resulted in smaller amounts of lactate but more formate, acetate, and ethanol, and approximately 1/10 of the maltose was found as β-glucose 1-phosphate in the medium. Furthermore, the β-PGM mutant cells grown on maltose were considerably larger and accumulated polysaccharides which consisted of α-1,4-bound glucose units. When the cells were grown at a low dilution rate in a glucose and maltose mixture, the wild-type strain exhibited a higher carbohydrate content than when grown at higher growth rates, but still this content was lower than that in the β-PGM mutant. In addition, significant differences in the initial metabolism of maltose and trehalose were found, and cell extracts did not digest free trehalose but only trehalose 6-phosphate, which yielded β-glucose 1-phosphate and glucose 6-phosphate. This demonstrates the presence of a novel enzymatic pathway for trehalose different from that of maltose metabolism in L. lactis.
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50

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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