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Maumau, Thandiwe Rebecca, Nobanathi Wendy Maxakato e Phumlani Fortune Msomi. "The Development of Anion Exchange Ionomer for Electrocatalysts in Application of Anion Exchange Membrane Fuel Cells". ECS Meeting Abstracts MA2022-02, n. 43 (9 ottobre 2022): 1613. http://dx.doi.org/10.1149/ma2022-02431613mtgabs.
Abstract (sommario):
Anion exchange membrane fuel cells (AEMFCs) are known to be able to address the use of expensive platinum catalyst by employing non-PGMs (Platinum Group Metal) metal catalysts, affordable ionomers, and greater fuel flexibility. All that provides AEMFCs with advantages over PEMFCs. However, AEMFCs have not been reported to achieve high current density as desired at fault by the lack of understanding of ionomer-catalyst interaction. For stable operation of AEM-based devices, water sorption and swelling of the thin anion exchange ionomer (AEI) layer are coupled to its catalyst binding ability. Unfortunately for AEM fuel cell field there exists no commercial material as Nafion® exists for the PEM fuel cell field. The development of a high performance and durable anionic catalyst binders also referred to as anion exchange ionomers (AEIs) is the major challenge for AEMFCs. This study aims to develop an improved AEI to be tested in both in-house and commercial electrocatalysts. Electrocatalytic activity using cyclic voltammetry (CV), linear sweep voltammetry (LSV), and chronoamperometry (CA) will be carried out for all the electrocatalysts with the use on the developed AEI instead of the usually used nafion ionomer. Characterization techniques will include transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) for particle size, crystal structure and morphology respectively of the electrocatalysts. For the developed AEI dynamic light scattering (DLS) (with an ELS-Z Zeta-potential and particle size analyzer), nuclear magnetic resonance (NMR), and Fourier-transform infrared spectroscopy (FTIR) for size distribution profile, material molecular structure and composition.
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Nallayagari, Ashwini Reddy, Frédéric Murphy, Maria Luisa Di Vona e Elena Baranova. "Investigation of Electrocatalyst and Ionomer Interaction in Anion Exchange Membrane Water Electrolysis". ECS Meeting Abstracts MA2023-02, n. 42 (22 dicembre 2023): 2067. http://dx.doi.org/10.1149/ma2023-02422067mtgabs.
Abstract (sommario):
Anion exchange membrane water electrolysis (AEMWE) is a type of electrolysis that involves the use of an anion exchange membrane (AEM) to separate the anode and cathode compartments. During the electrolysis process, water is split into hydrogen gas (H2) at the cathode and oxygen gas (O2) at the anode. AEMWE is an emerging technology that has the potential to play a significant role in the production of green hydrogen, which is a promising energy carrier for a variety of applications, including fuel cells and transportation. One of the benefits of AEMWE is that it can be used with a variety of water sources, including seawater and wastewater. Additionally, AEMWE has the potential to be more energy-efficient and cost-effective than other types of water electrolysis because it can operate at lower voltages and use cheap Ni-based materials [1]. Recently, there has been a significant amount of interest in the development of anion exchange ionomers (AEI) that conduct hydroxide ions [2]. We recently investigated the PPO-LC-TMA ionomer (poly(2,6-dimethyl-1,4-phenylene oxide) [3] backbone with amine-functionalized by trimethyl amine) [4] as an ionomer for Ni-based catalysts in AEMWE. Commercial Aemion, Fumion, and Nafion AEI were compared to the lab-synthesized ammonium-enriched anion exchange ionomer PPO-LC-TMA as an anode catalyst layer for oxygen evolution reaction (OER). Cyclic voltammetry results showed that the NiFe catalyst layer with PPO-LC-TMA AEI showed higher Ni(OH)2/NiOOH peak current density, while current density obtained over Ni90Fe10 catalysts was 11%, 17%, and 39% for Nafion, Fumion, and Aemion AEI, respectively [5]. This resulted in increased OER activity of Ni90Fe10 with PPO-LC-TMA AEI and a lower overpotential of 151 mV at 10 mA cm-2 in 1 M KOH. Ex-situ Raman spectroscopy of as prepared and spent catalytic layer confirmed that the electrode transitioned to the Ni-OOH phase after polarization. NiFe anode catalytic layers were tested in a 5 cm2 single-cell alkaline membrane water electrolysis (AEMWE) with varying amounts of PPO-LC-TMA (7, 15, and 25 wt %). AEMWE results revealed that 25 wt% PPO-LC-TMA is the best ionomer loading, achieving a cell voltage of 1.941 V at 600 mA cm-2 in 1 M KOH at 50°C. Both three-electrode electrochemical cell and alkaline membrane water electrolysis (AEMWE) tests revealed that the PPO-LC-TMA ionomer stabilized NiFe catalyst and improved its performance compared to Fumion and Nafion ionomers. These results will be presented and discussed, along with details of electrochemical and physical characterizations. References E. Cossar, F. Murphy, E.A. Baranova, J Chem Technol Biotechnol, 97 (2022) 1611–1624. Wright, A. G.; Fan, J.; Britton, B.; Weissbach, T.; Lee, H.-F.; Kitching, E. A.; Peckham, T. J.; Holdcroft, S. Energy Environ. Sci. 9 (2016) 2130−2142. A.R. Nallayagari, E. Sgreccia, L. Pasquini, M Sette, P. Knauth and M. L. Di Vona ACS Appl. Mater. Interfaces, 14, 41 (2022) 46537–46547. R.-A. Becerra-Arciniegas, R. Narducci, G. Ercolani, E. Sgreccia, L. Pasquini, M. L. Di Vona, and P. Knauth, J. Phys. Chem. C, 124, 2 (2020) 1309–1316. E. Cossar, F. Murphy, J. Walia, A. Weck, E.A. Baranova, ACS Applied Energy Materials, 5 (2022) 9938−9951.
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Kwen, Jiyun, Juan Herranz e Thomas J. Schmidt. "Forward-Bias 3D-Junction Bipolar Membranes for Electrochemical CO2 Reduction to CO". ECS Meeting Abstracts MA2023-02, n. 48 (22 dicembre 2023): 2438. http://dx.doi.org/10.1149/ma2023-02482438mtgabs.
Abstract (sommario):
The ongoing, rapid increase in atmospheric CO2 concentration has led to a growing interest in the electrochemical reduction of CO2 to value-added products like CO. To attain high current densities, the latter reaction is often performed using an anion exchange membrane(AEM) electrolyte that is well known to operate through the transport of (bi)carbonate ions from cathode to anode. This can in turn result in a CO2 pumping effect that decreases the device’s net CO2-consumption, and that can be prevented by using a bipolar membrane in a so-called forward-bias configuration (i.e., with the anion vs. cation exchange layers (AEL, CEL) contacting the cathode vs. anode electrodes, respectively). However, the recombination of protons and (bi)carbonate and concomitant production of H2O and CO2 at the AEL-CEL interface in this operative mode can also lead to the delamination of the membrane and cell failure. In order to prevent such a delamination, this study proposes the introduction of a three-dimensional (3D) AEL-CEL junction, utilizing Nafion® as the cation exchange layer and PiperION as the anion exchange one. Two different methods were applied to fabricate the 3D junction bipolar membrane. The first method involves the fabrication of a 3D interlocking layer using polystyrene (PS) beads that are sprayed (along with Nafion ionomer) onto a Nafion membrane, and removed using toluene. This results in an inverse-opal structure atop the Nafion membrane whose pores can be filled with anion exchange ionomer (AEI). Complementarily, the second method involves the introduction of a layer, consisting of a mixture of AEI and cation exchange ionomer (CEI) between the AEM and CEM. Additionally, a non-conductive oxide material is added to this ionomer layer to increase the contact area of AEI and CEI. Finally, the electrochemical CO2 reduction performance and durability of the resulting, 3D junction bipolar membranes are evaluated and compared to those of an equivalent, 2D junction bipolar membrane, in all cases in a forward bias configuration.
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Hyun, Jonghyun, e Hee-Tak Kim. "Ionomer Distribution Strategy of Anion Exchange Membrane Fuel Cell Catalyst Layer in Terms of Interaction between Catalyst Slurry Components". ECS Meeting Abstracts MA2022-01, n. 35 (7 luglio 2022): 1414. http://dx.doi.org/10.1149/ma2022-01351414mtgabs.
Abstract (sommario):
Anion exchange membrane fuel cells (AEMFCs) have been intensively studied in recent years to replace proton exchange membrane fuel cells (PEMFCs). The acid-to-alkali transitions have the potential to lower overall system costs because it allows the non-precious metal catalysts and inexpensive metal stack hardware. Significant strides have been made in materials science in the last few decades, particularly the development of high IEC-containing anion exchange membrane (AEM) and ionomer (AEI) possessing high OH- conductivity, enabling comparable cell performance to that of PEMFC. In addition, the discovery of high HOR activity of PtRu by oxophilic and/or electronic effects, and reducing ionomer poisoning, provided an opportunity to further advance the cell performance of AEMFC. However, despite the remarkable development of materials, modest AEMFCs still have inadequate power performance (< 0.5 W cm-2) even using the precious catalysts, which stems from a lack of understanding of the catalyst layer (CL) design. CL consists of a catalyst and an ionomer, where the chemical energy of the fuel is converted into electrical energy in triple-phase-boundaries (TPBs). TPB is an electrochemically active site where catalyst (electrons), ionomer (H+ or OH-), and reactant gases were concurrent. In order to realize a high-performance fuel cell, the TPB should be high enough to utilize the capabilities of the catalyst, and the ideal state would be to maximize the contact area between the ionomer and the catalyst while minimizing the loss of CL porosity. Accordingly, the structure of the CL is one of the key factors that directly affect the performance of the fuel cell and is in great account. CL is fabricated from a slurry containing a catalyst, ionomer, and dispersing solvent, whose structure is determined by the complex interactions between slurry components. Therefore, fine-tuning of comprehensive interaction (catalyst/ionomer, catalyst/solvent, and ionomer/solvent) is the core technology in CL design, and an in-depth understanding of each interaction is also essential. In this regard, we recently presented the rational design of the CL by controlling AEI size, distribution via a solvent selection of the catalyst slurry. Specifically, the larger the solubility parameter (excluding the hydrogen bonding term) of the organic solvent mixed with water, the smaller the dispersed AEI size, leading to an even distribution of the AEI in the CL. This induces a high electrochemical surface area of the CL, making it possible to achieve high performance AEMFC from the low current region. However, nevertheless, we found that the distribution of AEI in the AEMFC catalyst layer was still not completely uniform through various types of electron microscopy analysis. In particular, when the morphology of the AEMFC CL was compared with the Nafion ionomer (commonly used in PEMFC field) as a reference, AEI caused lower porosity by clogging the pores of Pt/C nanoparticles. For this reason, we found that AEMFCs had lower performance than Nafion-based PEMFCs, despite their high ORR activity under alkaline conditions. Molecular dynamics (MD) and density functional theory (DFT) simulation analyzes show that AEI has a particularly low interaction with carbon compared to Nafion, and for this reason, we found that AEI aggregates with each other rather than evenly distributed on the Pt/C surface. We used QPC-TMA as AEI in this study and confirmed that commercialized AEI (FAA-3 and XA-9) also form low CL porosity and pore-closing characteristics. This result suggests that low interaction between AEI/carbon is a universal property of current levels of AEI. Therefore, when designing an ionomer to improve the performance of AEMFC, high interaction with carbon should be considered as another important variable.
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Leonard, Daniel, Michelle Lehmann, Ivana Matanovic, Cy Fujimoto, Tomonori Saito e Yu Seung Kim. "Fundamental Insight into Phenyl-Free Polynorbornene Ionomers Enables High Performance Anion Exchange Membrane Fuel Cells". ECS Meeting Abstracts MA2023-01, n. 38 (28 agosto 2023): 2254. http://dx.doi.org/10.1149/ma2023-01382254mtgabs.
Abstract (sommario):
Anion exchange membrane fuel cells (AEMFCs) are seen as a possible successor to proton exchange membrane fuel cell technologies. A major motivation behind AEMFC development is the potential to use less costly materials, such as non-platinum group metal catalysts, thus reducing the stack cost. Anion exchange ionomers (AEIs) are polymers that facilitate ion transport in the catalyst layer play and a critical role in the performance of fuel cells. In fact, cell performance is profoundly affected by fundamental interactions between the catalyst surface and the AEI. Two such interactions are of particular importance: phenyl adsorption on hydrogen oxidation catalysts and electrochemical oxidation of phenyl moieties on oxygen evolution catalysts. Both are detrimental to an alkaline device’s performance and durability. We compared the adsorption energy of phenyl-containing ionomers for implementing phenyl-free ionomers. Density functional theory calculations indicated that the norbornane fragment has minimal adsorption energy on Pt(111) due to the absence of aromatic electrons. A soluble quaternized polynorbornene ionomer was prepared by vinyl addition polymerization. This ionomer enables high performance in fuel cells, (peak power density > 2 W cm-2), proving the advantage of the phenyl-free structure. This study establishes the phenyl adsorption energy-electrode performance relationship, highlighting the importance of material interactions between the catalysts and ionomers.
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Turtayeva, Zarina, Feina Xu, Régis Peignier, Alain Celzard e Gael Maranzana. "Optimization of Ionomer Content in Membrane Electrode Assemblies and Its Impact on the Performance in Anion Exchange Membrane Fuel Cells". ECS Meeting Abstracts MA2022-02, n. 43 (9 ottobre 2022): 1624. http://dx.doi.org/10.1149/ma2022-02431624mtgabs.
Abstract (sommario):
Anion exchange membrane fuel cells (AEMFCs) have recently attracted significant attention as low-cost alternative fuel cells to traditional proton exchange membrane fuel cells due to the possible use of platinum-group metal-free electrocatalysts [1]. Over the past decade, new materials dedicated to the alkaline medium, such as anion exchange membranes (AEMs) and anion exchange ionomers (AEIs), have been developed and studied in AEMFCs [2, 3]. However, only a few AEMs and AEIs are commercially available, and there are not ready to use catalyst coated membranes (CCMs) and/or gas diffusion electrodes (GDEs) with the wished AEMs or AEIs. In order to manufacture CCMs and/or GDEs on the basis of commercial materials, catalyst inks need to be prepared before testing them in AEMFC. It is well known that the composition of catalytic ink and the way to deposit it can influence the interaction between solvent, ionomer and catalyst particles during solvent evaporation and thus on the final structure and morphology of the catalyst layer. However, there are only a few papers dealing with catalyst layer compositions and structures for AEMFCs [4, 5], probably due to the recent development of alkaline fuel cells and new dedicated materials such as AEM and AEI. Since the ionomer/catalyst particle interface plays a crucial role in electrochemical reactions, it is essential to understand the impact of ionomer content on AEMFC performance as well as on water management. For this purpose, catalytic inks were prepared with different amounts of ionomer, ranging from 13 to 33 % in ratio. During this work, Pt / C (40 % in wt) catalyst as well as Aemion® membranes and ionomers were used. Different CCMs and GDEs were manufactured at 60 °C using a commercial ultrasonic spray coating bench. The morphology of the catalyst layers was characterized by scanning electron microscopy, and the thickness of the deposition was measured by a profilometer. Before testing in AEMFC, all prepared samples and membranes were converted to OH- form for 48 h in KOH 3M (the solution was changed every 12h). The performance of the prepared CCMs and GDEs was studied in a home-made AEMFC bench after an activation step. The results shown in Fig.1 highlight that: (i) the ionomer content in the catalyst layers affects the performance of the fuel cell, regardless of the coated support (membrane or GDL), (ii) concerning CCMs-based MEAs, the lower the ionomer content, the better the performance via the polarization curve, (iii) CCMs and GDEs-based MEAs do not behave similarly, (iv) GDEs-based MEAs show high OCV and high voltage for a given current density in comparison with CCMs-based MEAs, (v) concerning GDEs-based MEAs, the variation of the ionomer content in catalyst layer affects less the OCV value than the water management, and (vi) the water management of GDEs-based MEAs seems depend on the relative humidity of both gases and ionomer content in catalyst layers. This work is still under investigation. We will attempt to understand the relationship between the membrane/ionomer under different relative humidity and gas flow rates. [1] H. A. Firouzjaie and W. E. Mustain, “Catalytic Advantages, Challenges, and Priorities in Alkaline Membrane Fuel Cells,” ACS Catal., pp. 225–234, 2019, doi: 10.1021/acscatal.9b03892. [2] J. R. Varcoe et al., “Anion-exchange membranes in electrochemical energy systems †,” 2014, doi: 10.1039/c4ee01303d. [3] N. Chen and Y. M. Lee, “Anion exchange polyelectrolytes for membranes and ionomers,” Prog. Polym. Sci., vol. 113, p. 101345, Feb. 2021, doi: 10.1016/j.progpolymsci.2020.101345. [4] J. Hyun et al., “Tailoring catalyst layer structures for anion exchange membrane fuel cells by controlling the size of ionomer aggreates in dispersion,” Chem. Eng. J., vol. 427, no. August 2021, 2022, doi: 10.1016/j.cej.2021.131737. [5] P. Santori, A. Mondal, D. Dekel, and F. Jaouen, “The critical importance of ionomers on the electrochemical activity of platinum and platinum-free catalysts for anion-exchange membrane fuel cells,” R. Soc. Chem., vol. 2020, no. 7, pp. 3300–3307, doi: 10.1039/d0se00483aï. Figure 1
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Reddy, Nallayagari Ashwini. "Novel Metal-Free Composite Electrodes with Carbon Quantum Dots and Anion-Conducting Ionomers for the Oxygen Reduction Reaction". ECS Meeting Abstracts MA2022-02, n. 57 (9 ottobre 2022): 2172. http://dx.doi.org/10.1149/ma2022-02572172mtgabs.
Abstract (sommario):
The oxygen reduction reaction (ORR) is one of the bottlenecks in many electrochemical applications and plays an important role in commercial fuel cell systems. Platinum is highly used as a catalyzer especially in proton exchange membrane fuel cells. Given its rarity and cost, platinum, is not a viable choice as a catalyst, so there is a need to shift to alternative materials such as a metal-free catalyst possible in anion exchange membrane fuel cells. There were several theoretical and experimental studies to address this issue and a direction toward metal-free catalysts is of great interest. In this study, we focus on the oxygen reduction reaction in alkaline medium using a novel metal-free catalyst composite with carbon quantum dots and anion exchange ionomer (AEI). Doped carbon quantum dots were synthesized by a hydrothermal method and an AEI was integrated to improve the hydroxide ion transport and have a composite of desired functionality. These composites showed significant electrochemical activity with a good current response and four-electron ORR. The characterization comprised various microscopic, spectroscopic and electrochemical techniques. Figure 1
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Eriksson, Björn, Pietro Giovanni Santori, Nicolas Bibent, Frederic Lecoeur, Marc Dupont e Frederic Jaouen. "Shedding Light on Water Management during Operation of AEMFC with Humidity Sensors". ECS Meeting Abstracts MA2022-01, n. 35 (7 luglio 2022): 1462. http://dx.doi.org/10.1149/ma2022-01351462mtgabs.
Abstract (sommario):
The performance of anion exchange membrane fuel cells (AEMFC) has dramatically progressed in the past few years, with initial power performance matching, if not exceeding, those of proton exchange membrane fuel cells (PEMFC). The remaining challenges are i) the replacement of platinum-group-metal catalysts by catalysts based on Earth-abundant elements, ii) improved durability, and iii) the carbonatation issue when the cathode is fed with natural air. Compared to PEMFCs, the water management of AEMFC is more challenging, due to higher flux of water transported from one electrode to the other for a given current density, but also due to the high swelling of anion exchange ionomer (AEI) [1]. An optimized water management was shown to be not only critical for AEMFC power performance [2], but also for the cell stability. The chemical stability of AEM and AEI was recently shown to decrease dramatically with decreasing relative humidity [3]. During AEMFC operation, low humidity is expected on the cathode due to water consumption by the oxygen reduction reaction and due to electroosmotic drag from cathode to anode. While the water management of AEMFC is a recognized challenge, only few works have hitherto investigated it with operando techniques [4-5]. In this presentation, we will discuss the application of humidity sensors to measure on-line the relative humidity of the gas outlets of a single-cell AEMFC, allowing us to derive the water balance at each electrode (Figure 1a). The setup was applied to study the water balance and understand how it affects the AEMC power performance, focusing on one type of membrane-electrode assembly, comprising of a state-of-art anode (PtRu/C), cathode (Fe-N-C) and AEM/AEI (low density polyethylene/ethylenetetrafluoroethylene). The effect of dew point, backpressure and flow rates on cell performance and water transport were investigated. As an example of the type of results that can be obtained, Figure 1b shows the water balance at the anode and cathode as a function of time (blue and red curves, respectively), for different galvanostatic holds of 5 min each, from 0.2 to 1.2 A cm-2, at otherwise fixed conditions. As expected, the water balance is positive at the anode, and increases fairly linearly with the current density. Importantly, the water balance at the anode is always lower than the anode water balance expected if all the produced water (through the hydrogen oxidation reaction) would stay in the anode. This implies that the electroosmotic drag effect of water transport from cathode to anode is minor, and that the transport of water from anode to cathode (via back-diffusion, or other mechanism) is significant. As a result, the water balance is also positive at the cathode. Figure 1b shows also the total water balance (green curve), and that it matches with the theoretical total simply derived from the cell current density (black curve). In fact, for all operating conditions tested, the water balance was positive at the cathode, implying that the so-called cathode dry-out seldom occurs in AEMFC. The results also generally show that anode flooding is strongly connected with the maximum current density at which an AEMFC can stably operate. In conclusion, the use of humidity sensors can provide quantified insights on water dynamics in operating AEMFC, providing a tool for understanding optimized operating conditions, or for optimizing materials and components when they are designed to improve water management. References [1] J. R. Varcoe et al, Anion-exchange membrane in electrochemical energy systems, Energy & Environ. Science 7 (2014) 3135-3191 [2] N. Ul Hassan, M. Mandal, G. Huang, H. A. Firouzjaie, P. A. Kohl, W. E. Mustain, Achieving high performance and 200 h stability in anion exchange membrane fuel cells by manipulating ionomer properties and electrode optimization, Adv. Energy Materials 10 (2020) 2001986. [3] D. R. Dekel, M. Amar, S. Willdorf, M. Kosa, S. Dhara, C. E. Diesendruck, Effect of water on the stability of quaternary ammonium groups for anion exchange membrane fuel cell applications, Chem. Mater. 29 (2017) 4425-4431. [4] X. Peng et al, Using operando techniques to understand and design high performance and stable alkaline membrane fuel cells, Nature Commun. 11 (2020) 3561. [5] B. Eriksson, H. Grimler, A. Carlson, H. Ekström, R. Wreland Lindström, G. Lindbergh, C. Lagergren, Quantifying water transport in anion exchange membrane fuel cells, Int. J. Hydrogen Energy 44 (2019) 4930-4939. Acknowledgments This study was supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement CREATE [721065]. We are grateful to Prof. John R. Varcoe (Univ. Surrey, UK) for providing the ionomer and membrane Figure 1
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Varcoe, John, Rachida Bance-Souahli, Arup Chakraborty, Mehdi Choolaei, Carol Crean, Carlos Giron Rodriguez, Bjørt Óladóttir Joensen et al. "The Latest Developments in Radiation-Grafted Anion-Exchange Polymer Electrolytes for Low Temperature Electrochemical Systems". ECS Meeting Abstracts MA2022-01, n. 35 (7 luglio 2022): 1443. http://dx.doi.org/10.1149/ma2022-01351443mtgabs.
Abstract (sommario):
Anion-exchange membranes (AEM) are being developed for use in electrochemical technologies including fuel cells (AEMFC),water electrolysis (AEMWE for green hydrogen), electrolysers for CO2 reduction (CO2RR), and reverse electrodialysis (RED). Radiation-grafted AEMs (RG-AEM) represent a promising class of AEM that can exhibit high conductivities (OH- conductivities of > 200 mS cm-1 at temperatures above 60 °C) and favourable in situ water transport characteristics). Hence, RG-AEMs have shown significant promise when tested in AEMFCs alongside powdered radiation-grafted anion-exchange ionomers (RG-AEI), producing high performances and promising durabilities [Energy Environ. Sci., 12, 1575 (2019) and Nature Commun., 11, 3561 (2020)], even at temperatures above 100 °C [Dekel et al., J. Power Sources Adv., 5, 100023 (2020)]. An Achilles heel with RG-AEM types is that they can swell excessively in water and have large dimensional changes between the dehydrated and hydrated states. This limits the ion-exchange capacities (IEC) that can be used: excessive IECs in RG-AEM will cause excessive swelling and poorer robustness. This clearly indicates that additional crosslinking is needed. As Kohl et al. have highlighted, optimised crosslinking can lead to production of high-IEC AEMs that are both robust enough to be < 20 µm in thickness and also low swelling [e.g. J. Electrochem. Soc., 166, F637 (2019)], allowing truly world-leading AEMFC performances. RG-AEMs are also being used as a screening platform for down-selecting different (cationic) head-group chemistries for use in RED cells (a salinity gradient power technology), where different head-groups may lead to different AEM characteristics such as: in-cell resistance (when in contact with aqueous electrolytes), permselectivity, and fouling characteristics (when real world waters such as industrial brines, seawater and freshwater are used). It was evident very early on in these studies that RG-AEMs (desirably) exhibit extremely low resistances but also (undesirably) very low permselectivities when un-crosslinked (less than the required 90%+ permselectivity). Our work on RG-type cation-exchange membranes [Sustainable Energy Fuels, 3, 1682 (2019)] clearly shows that introduction of crosslinking can improve permselectivity. Crosslinking always involves a compromise, where its introduction can improve a membrane characteristic (e.g. reduced swelling or improved permselectivity) but also leads to lower conductivities or poorer transport of chemical species through the membranes. Hence, crosslinking types and levels need to be carefully controlled. With RG-AEMs (made by electron-beam activation (peroxidation) of inert polymer films, followed by grafting of monomers and post-graft amination), we have a choice of introducing crosslinking at various stages. The figure below summarises the two different approaches to crosslinking that will be discussed in the presentation: adding a divinyl-type crosslinker into the grafting mixture or adding a diamine-type crosslinker into the amination step. This presentation will present a selection of recent RG-AEM and RG-AEI developments from a number of projects: (1) REDAEM: AEMs for RED cells [EPSRC Grant EP/R044163/1]; (2) CARAEM: Novel RG-AEMs for AEMFCs and AEMWE [EPSRC Grant EP/T009233/1]; (3) SELECTCO2: RG-AEMs being tested in CO2RR cells [EU Horizon 2020 grant agreement 851441]. This presentation will show: (a) RG-AEMs made from thin high density polyethylene (HDPE) precursors appear better for application in AEMFCs, while RG-AEMs from made from thicker ETFE precursors appear to be better for CO2RR cells and RED; (b) RG-AEMs can be made using a variety of crosslinking strategies; (c) RG-AEIs can be made using ETFE powders and give optimal performance after cryogrinding down to micrometer sizes; Figure 1
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Osmieri, Luigi, Wilton Kort-Kamp, Haoran Yu, Deborah J. Myers, Raphael P. Hermann, David A. Cullen, Edward F. Holby e Piotr Zelenay. "Nickel Oxide-Aerogel Electrocatalysts for Oxygen Evolution Reaction in Alkaline Media: Experimental Approaches and Modeling-Assisted Strategies for Improving Performance and Durability". ECS Meeting Abstracts MA2023-02, n. 42 (22 dicembre 2023): 2149. http://dx.doi.org/10.1149/ma2023-02422149mtgabs.
Abstract (sommario):
Anion exchange membrane water electrolyzers (AEMWEs) represent an attractive technology for producing “green” hydrogen that enables operation on pure water using platinum group metal (PGM)-free electrocatalysts at both anode and cathode. Also, AEMWEs do not require the use of highly concentrated and corrosive alkaline electrolytes and PGM-based catalysts, which are the major drawbacks of the incumbent low-temperature liquid-alkaline and proton exchange membrane electrolyzers, respectively.1,2 In this context, the development of PGM-free electrocatalysts for oxygen evolution reaction (OER) in alkaline media has attracted considerable research interest. Among different types of transition metal-based oxides, Ni oxides doped with Fe have shown the highest OER activity in alkaline media.3,4 Recently, we have developed at Los Alamos National Laboratory (LANL) a series of Ni oxide-based aerogel materials that, primarily in combination with Fe in different proportions, have shown respectable OER performance in the electrochemical cell and at the AEMWE anode operating on either neat deionized water or with a supporting electrolyte, 0.1 M KOH or K2CO3.5 For application at the AEMWE anode, the catalyst integration into the electrode catalyst layer, i.e., combining the catalyst with anion exchange ionomer (AEI) and binding agents, is crucial to prevent catalyst layer delamination and to create a good catalyst/electrolyte interface, which in turn enables high OH- conductivity within the catalyst layer.6 This latter aspect is especially important for achieving high AEMWE performance in pure water operation. In this work, we investigate the impact of combining our Ni-Fe oxide aerogel catalysts with different AEIs (various backbone chemistries, OH- functional groups) and different binding agents (e.g., Nafion ionomer) on the AEMWE performance. We will show that full activation of the catalyst by phase transformation from the original Ni oxide-like structure to the active layered (oxy)hydroxide is essential for achieving high OER activity, and it can be influenced by the catalyst layer composition. By advanced characterization techniques such as high-resolution scanning transmission electron microscopy, X-ray absorption spectroscopy, and Mössbauer spectroscopy, we will shed light onto the phase transformation process that results in superior OER activity of these materials in alkaline media. Following our prior machine learning studies aimed at optimizing for the synthesis of oxygen reduction electrocatalysts,7,8 we will also show how to improve the synthesis of Ni oxide aerogel-based OER catalysts to maximize activity and stability. This work is further supported by density functional theory (DFT) modeling studies to better understand reaction mechanisms, active sites, and ultimately what role transition metal dopants (Fe and Co) play in modifying OER activity. Studies of in situ dissolution of these dopants using DFT-generated, phase-constrained Pourbaix diagrams9 will guide synthesis through understanding this likely materials degradation pathway. References H. A. Miller et al., Sustain. Energy Fuels, 4, 2114–2133 (2020). C. Santoro et al., ChemSusChem, 202200027 (2022). S. Fu et al., Nano Energy, 44, 319–326 (2018) D. Xu et al., ACS Catal., 9, 7–15 (2019). P. Zelenay and D. Myers, "ElectroCat (Electrocatalysis Consortium);” U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Program, 2022 Annual Merit Review and Peer Evaluation Meeting, June 6-8, 2022. https://www.hydrogen.energy.gov/pdfs/review22/fc160_myers_zelenay_2022_o.pdf L. Osmieri et al., J. Power Sources, 556, 232484 (2023). M. R. Karim et al., ACS Appl. Energy Mater., 3, 9083–9088 (2020). W. J. M. Kort-Kamp et al., J. Power Sources, 559 (2023). E. F. Holby, G. Wang, and P. Zelenay, ACS Catal., 10, 14527–14539 (2020).
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Gao, Xueqiang, Hongmei Yu, Jia Jia, Jinkai Hao, Feng Xie, Jun Chi, Bowen Qin, Li Fu, Wei Song e Zhigang Shao. "High performance anion exchange ionomer for anion exchange membrane fuel cells". RSC Advances 7, n. 31 (2017): 19153–61. http://dx.doi.org/10.1039/c7ra01980g.
Abstract (sommario):
The anion exchange ionomer incorporated into the electrodes of an anion exchange membrane fuel cell (AEMFC) enhances anion transport in the catalyst layer of the electrode, and thus improves performance and durability of the AEMFC.
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Kwak, Minkyoung, Kasinath Ojha e Shannon W. Boettcher. "(Invited) Passivated Anodes in Anion-Exchange Membrane Water Electrolyzers". ECS Meeting Abstracts MA2023-01, n. 36 (28 agosto 2023): 2052. http://dx.doi.org/10.1149/ma2023-01362052mtgabs.
Abstract (sommario):
Understanding and engineering the catalyst-electrolyte interface are important for many electrochemical devices. In anion exchange membrane water electrolysis (AEMWE) specifically, the durability of the system is limited by substantial oxidative ionomer degradation at the anodic potentials for oxygen evolution reaction (OER) at the anode. We understand that oxidative ionomer degradation at the anodes is due to the electron transfer from ionomer to the electrode as there is electrical contact between catalysts and ionomers. Here a thin layer of transition metal oxide coating is applied as a passivation (insulating) layer at the catalyst-ionomer interface at the anodes to suppress ionomer degradation and enhance the durability of AEMWE. We investigate the optimal thickness of the metal oxide coatings in Ir- and Co-based electrode systems and observe that the thin layer of metal oxide films on top of the catalyst layers improves the voltage degradation and protects ionomer from oxidative degradation. This work helps us understand the interaction between catalysts and ionomers and solve the durability problems in AEMWE systems using interfacial engineering.
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Gonçalves Biancolli, Ana Laura, Daniel Herranz, Lianqin Wang, Gabriela Stehlíková, Rachida Bance-Soualhi, Julia Ponce-González, Pilar Ocón et al. "ETFE-based anion-exchange membrane ionomer powders for alkaline membrane fuel cells: a first performance comparison of head-group chemistry". Journal of Materials Chemistry A 6, n. 47 (2018): 24330–41. http://dx.doi.org/10.1039/c8ta08309f.
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Sebastián, David, Giovanni Lemes, José M. Luque-Centeno, María V. Martínez-Huerta, Juan I. Pardo e María J. Lázaro. "Optimization of the Catalytic Layer for Alkaline Fuel Cells Based on Fumatech Membranes and Ionomer". Catalysts 10, n. 11 (20 novembre 2020): 1353. http://dx.doi.org/10.3390/catal10111353.
Abstract (sommario):
Polymer electrolyte fuel cells with alkaline anion exchange membranes (AAEMs) have gained increasing attention because of the faster reaction kinetics associated with the alkaline environment compared to acidic media. While the development of anion exchange polymer membranes is increasing, the catalytic layer structure and composition of electrodes is of paramount importance to maximize fuel cell performance. In this work, we examine the preparation procedures for electrodes by catalyst-coated substrate to be used with a well-known commercial AAEM, Fumasep® FAA-3, and a commercial ionomer of the same nature (Fumion), both from Fumatech GmbH. The anion exchange procedure, the ionomer concentration in the catalytic layer and also the effect of membrane thickness, are investigated as they are very relevant parameters conditioning the cell behavior. The best power density was achieved upon ion exchange of the ionomer by submerging the electrodes in KCl (isopropyl alcohol/water solution) for at least one hour, two exchange steps, followed by treatment in KOH for 30 min. The optimum ionomer (Fumion) concentration was found to be close to 50 wt%, with a relatively narrow interval of functioning ionomer percentages. These results provide a practical guide for electrode preparation in AAEM-based fuel cell research.
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Rossini, Matteo, Burak Koyuturk, Björn Eriksson, Amirreza Khataee, Göran Lindbergh e Ann Cornell. "Rational Design of Membrane Electrode Assembly for Anion Exchange Water Electrolysis". ECS Meeting Abstracts MA2023-01, n. 36 (28 agosto 2023): 2059. http://dx.doi.org/10.1149/ma2023-01362059mtgabs.
Abstract (sommario):
In the framework of an increased interest for green hydrogen production, Anion Exchange Membrane Water Electrolysis (AEMWE) systems have attracted tremendous attention. Platinum group metal-free (PGM-free) catalysts can be effectively exploited with this technology to reach higher current densities compared to traditional alkaline electrolysis [1]. However, challenges are posed by the stability of the anion conducting polymer in the membrane and in the catalyst layers (CLs). Furthermore, the scarcity of works showing devices with stable performance which can work without a supporting electrolyte raises the question of whether or not it is possible to rely on ionomer conductivity for CL. Here, we focus on a method for the fabrication of catalyst coated membranes (CCMs). This strategy has the benefit of enhancing the interfacial contact between the CL and the membrane, reducing the cell resistance when low conducting electrolytes or pure water are used. Inspired by the industrial approach for proton exchange membrane (PEM) fuel cell fabrication, we applied the “decal transfer” method to AEMWE. In this approach, the CL is first coated on a substrate and then transferred on the membrane surface to fabricate the so-called MEA. This method is easy to scale up and allows for fine control of catalyst loading. In our work, we investigated the effect of ionomer content on the electrode performance. After optimizing the ionomer weight fraction for both anode and cathode, we studied the stability of MEAs at 200 mA/cm2 in 1 M KOH. It was found that when the anion conducting ionomer (AP-1-HNN8-00-X) in the anode CLs was replaced with Nafion, the electrode performance (Figure 1a) and stability were significantly improved (Figure 1b). Additionally, the electrode utilization was increased due to the higher density and lower water uptake of Nafion which reduces the volume fraction of Nafion in the CL. Reduced electrode resistance was also observed using Nafion when compared to the anion exchange ionomer (figure 1a). Since Nafion is chemically stable and does not suffer from excessive water uptake and dissolution, contrary to anion exchange ionomers [2], it can be easily used as a binder in AEMWE. These findings point out that MEAs for AEMWE can be manufactured with the “decal” method, however, their performance is limited by the catalyst surface area and ionomer stability. These two elements are fundamental towards pure water AEMWE. References [1] Miller, Hamish Andrew, Karel Bouzek, Jaromir Hnat, Stefan Loos, Christian Immanuel Bernäcker, Thomas Weißgärber, Lars Röntzsch, and Jochen Meier-Haack. “Green Hydrogen from Anion Exchange Membrane Water Electrolysis: A Review of Recent Developments in Critical Materials and Operating Conditions.” Sustainable Energy & Fuels 4, no. 5 (2020). [2] Chen, Binyu, Peter Mardle, and Steven Holdcroft. “Probing the Effect of Ionomer Swelling on the Stability of Anion Exchange Membrane Water Electrolyzers.” Journal of Power Sources 550 (December 2022). Figure 1 A) Polarization curve of MEAs with anion exchanging ionomer (AP-1-HNN8-00-X) (red) in the anode CL and with Nafion (blue). B) Stability test of the MEAs at 200 mA/cm2. The cathode catalyst layer has the same composition in both cases and contains 20% anion exchange ionomer. The measurements are conducted in 1 M KOH at 60 °C. Figure 1
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Park, Habin, Hui Min Tee, Parin Shah, Chandler Dietrich e Paul Kohl. "Durability and Performance of Poly(norbornene) Membranes and Ionomers in Alkaline Electrolyzers". ECS Transactions 111, n. 4 (19 maggio 2023): 13–19. http://dx.doi.org/10.1149/11104.0013ecst.
Abstract (sommario):
The anion conductive ionomer in the oxygen-producing anode is a critical part of the three-dimensional electrode in the anion exchange membrane alkaline electrolysis. In this study, self-adhesive anode ionomers were designed to chemical bond the anode catalyst particles to the porous transport layer and to the ionomer. It was found that high ion exchange capacity ionomers were not needed for effective electrode polarization because the anode was fed with alkaline electrolyte through the flow channel. The hydrophobic nature of anode ionomer and intimate contact with the catalyst by chemical bonding to the catalyst was key to improving anodic polarization and cell durability. The catalyst and self-adhesive ionomer contents of anode were optimized for the mechanically durable and energy-efficient alkaline water electrolysis.
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Shang, Zhihao, Ryszard Wycisk e Peter Pintauro. "Electrospun Composite Proton-Exchange and Anion-Exchange Membranes for Fuel Cells". Energies 14, n. 20 (15 ottobre 2021): 6709. http://dx.doi.org/10.3390/en14206709.
Abstract (sommario):
A fuel cell is an electrochemical device that converts the chemical energy of a fuel and oxidant into electricity. Cation-exchange and anion-exchange membranes play an important role in hydrogen fed proton-exchange membrane (PEM) and anion-exchange membrane (AEM) fuel cells, respectively. Over the past 10 years, there has been growing interest in using nanofiber electrospinning to fabricate fuel cell PEMs and AEMs with improved properties, e.g., a high ion conductivity with low in-plane water swelling and good mechanical strength under wet and dry conditions. Electrospinning is used to create either reinforcing scaffolds that can be pore-filled with an ionomer or precursor mats of interwoven ionomer and reinforcing polymers, which after suitable processing (densification) form a functional membrane. In this review paper, methods of nanofiber composite PEMs and AEMs fabrication are reviewed and the properties of these membranes are discussed and contrasted with the properties of fuel cell membranes prepared using conventional methods. The information and discussions contained herein are intended to provide inspiration for the design of high-performance next-generation fuel cell ion-exchange membranes.
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Lee, Ji-Min, e Moon-Sung Kang. "Heterogeneous Anion-Exchange Membranes with Enhanced Ion Conductivity for Continuous Electrodeionization". Membranes 13, n. 12 (27 novembre 2023): 888. http://dx.doi.org/10.3390/membranes13120888.
Abstract (sommario):
In this study, the optimal fabrication parameters of a heterogeneous anion-exchange membrane (AEM) using an ionomer binder are investigated to improve the performance of continuous electrodeionization (CEDI) for producing ultrapure water. Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) is selected as the base material for preparing the ionomer binder and quaternized to have various ion exchange capacities (IECs). The optimal content of ion-exchange resin (IER) powder according to the IEC of the ionomer binder is then determined through systematic analyses. In conclusion, it is revealed that a heterogeneous AEM with optimal performance can be fabricated when the IEC of the ionomer binder is lowered and the content of IER powder is also lower than that of conventional heterogeneous membranes. Moreover, crosslinked quaternized PPO (QPPO) nanofiber powder is used as an additive to improve ion conductivity without deteriorating the mechanical properties of the membrane. The membrane fabricated under optimal conditions exhibits significantly lower electrical resistance (4.6 Ω cm2) despite a low IER content (30 wt%) compared to the commercial membrane (IONAC MA-3475, 13.6 Ω cm2) while also demonstrating moderate tensile strength (9.7 MPa) and a high transport number (ca. 0.97). Furthermore, it is proven that the prepared membrane exhibits a superior ion removal rate (99.86%) and lower energy consumption (0.35 kWh) compared to the commercial membrane (99.76% and 0.4 kWh, respectively) in CEDI experiments.
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Poynton, Simon D., Robert C. T. Slade, Travis J. Omasta, William E. Mustain, Ricardo Escudero-Cid, Pilar Ocón e John R. Varcoe. "Preparation of radiation-grafted powders for use as anion exchange ionomers in alkaline polymer electrolyte fuel cells". J. Mater. Chem. A 2, n. 14 (2014): 5124–30. http://dx.doi.org/10.1039/c4ta00558a.
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Klein, Jeffrey Michael, Ivana Matanovic, Michelle Lehmann, Tomonori Saito e Yu Seung Kim. "(Invited) Impact of Phenyl Adsorption of Various Ionomers on the Performance of Anion Exchange Membrane Water Electrolyzers". ECS Meeting Abstracts MA2023-01, n. 36 (28 agosto 2023): 2033. http://dx.doi.org/10.1149/ma2023-01362033mtgabs.
Abstract (sommario):
In this presentation, design principals of ionomeric binders for anion exchange membrane water electrolysis (AEMWE) will be discussed. The crucial impact of phenyl adsorption on AEMWE performance is highlighted with poly(terphenylene), poly(fluorene), poly(aryl piperidinium), or polynorbonene ionomers. Adsorption energies to hydrogen oxidation catalyst surfaces, calculated by density functional theory, demonstrate the utility in the phenyl free ionomer structure wherein lower adsorption energies yield improved AEMWE performance.1,2 Polarization curves with higher adsorption energy ionomers show a nonlinear transition to mass transport limited behavior at cell potentials above 1.68 V. Alternatively, mass transport limitations are absent when using the phenyl free ionomer, polynorbonene.3 Furthermore, polarization curves in 1 M NaOH of all studied systems begin to overlap suggesting that the phenyl oxidation on the oxygen evolution catalyst may be a primary influence on the transition to mass transport limits in AEMWE. Recent progress in both ionomer and AEM development at LANL for improved performance and durability of AEMWE, specifically with regard to limiting phenyl oxidation, will be discussed. 1 Matanovic, I. et al. Adsorption of Polyaromatic Backbone Impacts the Performance of Anion Exchange Membrane Fuel Cells. Chemistry of Materials 31, 4195-4204, doi:10.1021/acs.chemmater.9b01092 (2019). 2 Motz, A. R. et al. Performance and durability of anion exchange membrane water electrolyzers using down-selected polymer electrolytes. Journal of Materials Chemistry A 9, 22670-22683, doi:10.1039/D1TA06869E (2021). 3 Huang, G. et al. Ionomer Optimization for Water Uptake and Swelling in Anion Exchange Membrane Electrolyzer: Oxygen Evolution Electrode. Journal of The Electrochemical Society 167, 164514, doi:10.1149/1945-7111/abcde3 (2020).
21
He, Cheng, Ami C. Yang-Neyerlin e Bryan S. Pivovar. "Probing Anion Exchange Membrane Fuel Cell Cathodes by Varying Electrocatalysts and Electrode Processing". Journal of The Electrochemical Society 169, n. 2 (1 febbraio 2022): 024507. http://dx.doi.org/10.1149/1945-7111/ac4daa.
Abstract (sommario):
To date, several high-performing anion exchange membrane fuel cells (AEMFCs) have been demonstrated, but most these studies have focused on Pt containing cathodes with high loadings. Here, we explore and compare the performance and perform electrochemical diagnostics on three leading AEMFC cathode electrocatalysts: Pt/C, Ag/C, and Fe–N–C with electrodes that have been processed with either powder or dispersion-based ionomers using perfluorinated anion exchange polymers. Pt/C had the highest performance but also showed a strong dependence on ionomer type, with powder ionomer exhibiting much higher performance. These results were consistent with the observations for Ag/C but did not hold for the Fe–N–C catalyst where almost no change was observed between powder and dispersion-based ionomers. This is the first-time the impact of powder and dispersion ionomer with different classes of cathode electrocatalysts on the fuel cell performance have been compared, and the results have strong implications for the ability to achieve high performance at low loadings and for better understanding catalyst-ionomer interactions within AEMFCs.
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Koch, Susanne, Philipp A. Heizmann, Sophia K. Kilian, Benjamin Britton, Steven Holdcroft, Matthias Breitwieser e Severin Vierrath. "The effect of ionomer content in catalyst layers in anion-exchange membrane water electrolyzers prepared with reinforced membranes (Aemion+™)". Journal of Materials Chemistry A 9, n. 28 (2021): 15744–54. http://dx.doi.org/10.1039/d1ta01861b.
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Koch, Susanne, Joey Disch, Sophia K. Kilian, Yiyong Han, Lukas Metzler, Alessandro Tengattini, Lukas Helfen, Michael Schulz, Matthias Breitwieser e Severin Vierrath. "Water management in anion-exchange membrane water electrolyzers under dry cathode operation". RSC Advances 12, n. 32 (2022): 20778–84. http://dx.doi.org/10.1039/d2ra03846c.
Abstract (sommario):
Dry cathode operation is a desired operation mode in anion-exchange membrane water electrolyzers, but water management is crucial. This is visualized using high-resolution neutron radiography and the ion-exchange capacity of the cathode ionomer is varied.
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Mayerhöfer, Britta, Konrad Ehelebe, Florian D. Speck, Markus Bierling, Johannes Bender, Jochen A. Kerres, Karl J. J. Mayrhofer, Serhiy Cherevko, Retha Peach e Simon Thiele. "On the effect of anion exchange ionomer binders in bipolar electrode membrane interface water electrolysis". Journal of Materials Chemistry A 9, n. 25 (2021): 14285–95. http://dx.doi.org/10.1039/d1ta00747e.
Abstract (sommario):
Bipolar interfaces located directly between a proton conducting membrane and an anion exchange ionomer based anode catalyst layer are investigated in membrane electrode assemblies for water electrolysis.
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Veh, Philipp, Benjamin Britton, Steven Holdcroft, Roland Zengerle, Severin Vierrath e Matthias Breitwieser. "Improving the water management in anion-exchange membrane fuel cells via ultra-thin, directly deposited solid polymer electrolyte". RSC Advances 10, n. 15 (2020): 8645–52. http://dx.doi.org/10.1039/c9ra09628k.
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Li, Xiuhua, Jinxiong Tao, Guanghui Nie, Liuchan Wang, Liuhong Li e Shijun Liao. "Cross-linked multiblock copoly(arylene ether sulfone) ionomer/nano-ZrO2 composite anion exchange membranes for alkaline fuel cells". RSC Adv. 4, n. 78 (2014): 41398–410. http://dx.doi.org/10.1039/c4ra06519k.
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Park, Yoo Sei, Myeong Je Jang, Jae-Yeop Jeong, Jooyoung Lee, Jaehoon Jeong, Chiho Kim, Juchan Yang e Sung Mook Choi. "Optimization of Ionomer Content in Anode Catalyst Layer for Improving Performance of Anion Exchange Membrane Water Electrolyzer". International Journal of Energy Research 2023 (8 novembre 2023): 1–10. http://dx.doi.org/10.1155/2023/3764096.
Abstract (sommario):
Anion exchange membrane (AEM) water electrolyzers, which are considered next-generation hydrogen production energy devices, generate hydrogen using a nonprecious metal as the electrocatalyst. However, most current studies tend to focus on the development of highly active electrocatalysts based on nonprecious metals, and there have been few attempts to develop improved electrodes for these devices. In particular, the catalyst layer of the electrode is the key component that directly affects the performance of AEM electrolyzers. In this study, we developed a high-performance anode for the AEM water electrolyzer by optimizing the ionomer content of the anode catalyst layer. In particular, the electrochemical behavior of the AEM electrolyzer was systematically analyzed while varying the amount of ionomer present within the anode catalyst layer. The ionomer content significantly affects the ohmic and mass transport losses of the AEM electrolyzer and consequently plays an important role in determining its performance. Upon employing the optimized ionomer, a current density of 1.44 A/cm2 was achieved at 1.8 V, representing a 25% improvement compared to using a nonoptimized ionomer. In addition, the ionomer content also significantly affects the durability of the system. Thus, this study highlights the importance of developing improved electrodes for the realization of high-performance AEM water electrolyzers.
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Yang, Zhengjin, Yazhi Liu, Rui Guo, Jianqiu Hou, Liang Wu e Tongwen Xu. "Highly hydroxide conductive ionomers with fullerene functionalities". Chemical Communications 52, n. 13 (2016): 2788–91. http://dx.doi.org/10.1039/c5cc09024e.
Abstract (sommario):
A novel ionomer was designed that will not poison the catalyst in alkaline fuel cells, by incorporating for the first time N-methyl pyrrolidine-C60 cation in polymeric anion exchange ionomers.
29
Li, Yan, Jujia Zhang, Hua Yang, Shanzhong Yang, Shanfu Lu, Haibing Wei e Yunsheng Ding. "Boosting the performance of an anion exchange membrane by the formation of well-connected ion conducting channels". Polymer Chemistry 10, n. 22 (2019): 2822–31. http://dx.doi.org/10.1039/c9py00011a.
Abstract (sommario):
Enlarging the discrepancies between hydrophilic/hydrophobic segments in the chemical structure of an ionomer proved to be an efficient strategy to induce the formation of a microphase-separated morphology of the resulting anion exchange membrane.
30
Narducci, Riccardo. "(Invited) Anion Exchange Membrane Fuel Cells in LIME Laboratory: From Commercial Polymers Towards Biomass Based Materials". ECS Meeting Abstracts MA2022-02, n. 41 (9 ottobre 2022): 1505. http://dx.doi.org/10.1149/ma2022-02411505mtgabs.
Abstract (sommario):
Anion exchange membrane fuel cells (AEMFCs) are clean energy conversion devices that are an attractive alternative to the more common proton exchange membrane fuel cells, because they present the advantage of not using noble metals as catalysts for the oxygen reduction reaction (ORR). Unfortunately the low durability of anion exchange membranes (AEMs) in basic conditions limits their use on a large scale. The International Laboratory "Ionomer Materials for Energy" (LIME) group has extensively worked on synthesis of ionomers applying different strategies to mitigate the damaging effect of alkaline media on anion exchange membranes: the delocalization of the positive charge, the introduction of a long chain to separate the charge and the backbone [1], the introduction of a second phase, backbone without ether groups, and recently the use of biomass to prepare more sustainable materials for fuel cells. In this presentation, after a short overview on the progress made on anionic membranes based on commercial polymers, such as polysulfone (PSU) and poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) [2], I will focalize on the synthesis of the new ionomer poly(alkylene biphenyl butyltrimethyl ammonium) (ABBA) with a backbone devoid of alkaline-labile C-O-C bonds and with quaternary ammonium groups grafted on long side chains [3]. The ionomer was achieved by metalation reaction on 2-bromobiphenyl, followed by the introduction of the long chain with 1,4-dibromobutane. The precursor was polycondensed and then quaternized using trimethylamine (TMA). The reaction is efficient, well controllable and easy to modulate. The ability to form stable solutions over several months, combined with the spacing of the positive charge from the backbone, the flexibility due to the quaternary carbon in the matrix and the high IEC values such as 2.5 meq/g, allows us to consider this ionomer a good candidate as an electrode binder and AEM. Other synthesis of backbones without ether linkage was explored e.g. a crosslinked poly(vinylbenzylchloride-co-hexene) copolymer grafted with N,N-dimethylhexylammonium groups [4]. The copolymerization was achieved by the Ziegler–Natta method, employing the complex ZrCl4 (THF)2 as a catalyst. The resulting aliphatic ionomer showed good alkaline stability, after 72 h of treatment in 2M KOH at 80 °C the remaining IEC of 76% confirmed that ionomers without ether bonds are less sensitive to a SN2 attack. The ionic conductivity of blended membrane with polyvinyl alcohol (PVA) at 25 °C in the OH− form was 29.5 mS/cm. The last part of presentation will be focus on a more sustainable fuel cell, based on heterocycle building blocks exploiting biomass resources. References [1] R.A. Becerra-Arciniegas, R. Narducci, G. Ercolani, E. Sgreccia, L. Pasquini, M.L. Di Vona, P. Knauth, Model Long Side-Chain PPO-Based Anion Exchange Ionomers: Properties and Alkaline Stability, Journal of Physical Chemistry C 124(2) (2020) 1309-1316. [2] P. Knauth, L. Pasquini, R. Narducci, E. Sgreccia, R.A. Becerra-Arciniegas, M.L. Di Vona, Effective ion mobility in anion exchange ionomers: Relations with hydration, porosity, tortuosity, and percolation, Journal of Membrane Science 617 (2021) 118622. [3] R. Narducci, R.A. Becerra-Arciniegas, L. Pasquini, G. Ercolani, P. Knauth, M.L. Di Vona, Anion-Conducting Polymer Electrolyte without Ether Linkages and with Ionic Groups Grafted on Long Side Chains: Poly(Alkylene Biphenyl Butyltrimethyl Ammonium) (ABBA), Membranes 12(3) (2022) 337. [4] R.A. Becerra-Arciniegas, R. Narducci, G. Ercolani, L. Pasquini, P. Knauth, M.L. Di Vona, Aliphatic Anion Exchange Ionomers with Long Spacers and No Ether Links by Ziegler-Natta Polymerization: Properties and Alkaline Stability, Molecules 27(2) (2022) 395.
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Yanagi, Hiroyuki, e Kenji Fukuta. "Anion Exchange Membrane and Ionomer for Alkaline Membrane Fuel Cells (AMFCs)". ECS Transactions 16, n. 2 (18 dicembre 2019): 257–62. http://dx.doi.org/10.1149/1.2981860.
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Khadke, Prashant Subhas, e Ulrike Krewer. "Mass-Transport Characteristics of Oxygen at Pt/Anion Exchange Ionomer Interface". Journal of Physical Chemistry C 118, n. 21 (19 maggio 2014): 11215–23. http://dx.doi.org/10.1021/jp5011549.
33
Yassin, Karam, Igal G. Rasin, Simon Brandon e Dario R. Dekel. "Elucidating the role of anion-exchange ionomer conductivity within the cathode catalytic layer of anion-exchange membrane fuel cells". Journal of Power Sources 524 (marzo 2022): 231083. http://dx.doi.org/10.1016/j.jpowsour.2022.231083.
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Yassin, Karam, Igal Rasin, Simon Brandon e Dario R. Dekel. "Elucidating the Role of Anion-Exchange Ionomer Conductivity within the Cathode Catalytic Layer of Anion Exchange Membrane Fuel Cells". ECS Meeting Abstracts MA2021-02, n. 40 (19 ottobre 2021): 1204. http://dx.doi.org/10.1149/ma2021-02401204mtgabs.
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Akter, Mahamuda, Jiyun Shin, Jong-Hyeok Park, Soryong Chae e Jin Soo Park. "Alkaline-Stable Anion Conducting Ionomers for Anion Exchange Membrane Water Electrolyzers". ECS Meeting Abstracts MA2023-01, n. 36 (28 agosto 2023): 2000. http://dx.doi.org/10.1149/ma2023-01362000mtgabs.
Abstract (sommario):
Water electrolysis is a process that uses renewable energy to decompose water into oxygen and hydrogen. It is one of the most promising alternatives to produce and store new energy from renewable energy resources. In this study, pore-filled anion exchange membranes (PFAEMs) were prepared by using quaternary ammonia groups along with various cross-linker groups with different chain lengths and using porous polyethylene substrates which were pretreated from hydrophobic into hydrophilic using surfactants. The conductivity of the anion exchange membranes was measured by the in-plane cell and through-plane at room temperature or 60 ℃. In addition, the characterizations of anion exchange membranes such as water uptake, swelling ratio, mechanical strength, contact angle and TGA were carried out. As a result, the PFAEM exhibited remarkably high ion conductivity at extremely low areal swelling ratio and excellent chemical stability in a NaOH solution for 500 h. As an essential component of anion exchange membrane water electrolyzers, catalyst layers prepared by the catalyst inks comprising of ionomer binder and electrocatalysts are sandwiched between the anion exchange membrane to form a membrane electrode assembly in order to evaluate its impedance and I-V polarization curves. Acknowledgment This research was supported in part by the New and Renewable Energy of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) granted financial resource from the Ministry of Trade, Industry & Energy, Republic of Korea (No. 20213030040520) and by 2021 Green Convergence Professional Manpower Training Program of the Korea Environmental Industry and Technology Institute funded by the Ministry of Environment.
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Lo Vecchio, Carmelo, Alessandra Carbone, Stefano Trocino, Irene Gatto, Assunta Patti, Vincenzo Baglio e Antonino Salvatore Aricò. "Anionic Exchange Membrane for Photo-Electrolysis Application". Polymers 12, n. 12 (15 dicembre 2020): 2991. http://dx.doi.org/10.3390/polym12122991.
Abstract (sommario):
Tandem photo-electro-chemical cells composed of an assembly of a solid electrolyte membrane and two low-cost photoelectrodes have been developed to generate green solar fuel from water-splitting. In this regard, an anion-exchange polymer–electrolyte membrane, able to separate H2 evolved at the photocathode from O2 at the photoanode, was investigated in terms of ionic conductivity, corrosion mitigation, and light transmission for a tandem photo-electro-chemical configuration. The designed anionic membranes, based on polysulfone polymer, contained positive fixed functionalities on the side chains of the polymeric network, particularly quaternary ammonium species counterbalanced by hydroxide anions. The membrane was first investigated in alkaline solution, KOH or NaOH at different concentrations, to optimize the ion-exchange process. Exchange in 1M KOH solution provided high conversion of the groups, a high ion-exchange capacity (IEC) value of 1.59 meq/g and a hydroxide conductivity of 25 mS/cm at 60 °C for anionic membrane. Another important characteristic, verified for hydroxide membrane, was its transparency above 600 nm, thus making it a good candidate for tandem cell applications in which the illuminated photoanode absorbs the highest-energy photons (< 600 nm), and photocathode absorbs the lowest-energy photons. Furthermore, hydrogen crossover tests showed a permeation of H2 through the membrane of less than 0.1%. Finally, low-cost tandem photo-electro-chemical cells, formed by titanium-doped hematite and ionomer at the photoanode and cupric oxide and ionomer at the photocathode, separated by a solid membrane in OH form, were assembled to optimize the influence of ionomer-loading dispersion. Maximum enthalpy (1.7%), throughput (2.9%), and Gibbs energy efficiencies (1.3%) were reached by using n-propanol/ethanol (1:1 wt.) as solvent for ionomer dispersion and with a 25 µL cm−2 ionomer loading for both the photoanode and the photocathode.
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Leonard, Daniel P., Sandip Maurya, Eun Joo Park, Luis Delfin Manriquez, Sangtaik Noh, Xiaofeng Wang, Chulsung Bae, Ehren D. Baca, Cy Fujimoto e Yu Seung Kim. "Asymmetric electrode ionomer for low relative humidity operation of anion exchange membrane fuel cells". Journal of Materials Chemistry A 8, n. 28 (2020): 14135–44. http://dx.doi.org/10.1039/d0ta05807f.
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Kanaan, Riham, Pedro Henrique Affonso Nóbrega e Christian Beauger. "Hydrogen Reconversion from Ammonia through Anion Exchange Membrane Electrolysis". ECS Meeting Abstracts MA2023-01, n. 38 (28 agosto 2023): 2272. http://dx.doi.org/10.1149/ma2023-01382272mtgabs.
Abstract (sommario):
Nitrogen-based compounds, especially ammonia, is a promising alternative for the storage and transport of renewable hydrogen over long distances [1]. Considering ammonia as a hydrogen carrier will require studying the conversion (ammonia to hydrogen) and reconversion steps (hydrogen to ammonia). The reconversion of ammonia can take place through electrolysis under alkaline conditions [2] and needs the development of more efficient catalysts. For this, we started studying the electro-oxidation of ammonia in an anion exchange membrane electrolyser over platinum-based and PGM free electrodes with KOH as electrolyte. We have prepared several catalysts, carbon supported platinum, platinum-iridium, and nickel nanoparticles using the polyol technique. Commercial carbon supported platinum nanoparticles was used as catalyst for the cathodes. Catalyst coated substrates (CCS) were then prepared by spraying a catalytic ink over stainless-steel fiber paper for the anode side. The formulation of the ink requires optimizing parameters such as the type of ionomer (nafion, sustanion) and the ratio of ionomer to carbon. Anodes obtained have been assembled with anion exchange membranes and commercial cathodes for ammonia electro-oxidation in single cell. We have compared the performance of these different membrane electrodes assemblies (MEAs) to commercially available ones integrating nickel-iron-cobalt based anodes. The performance of MEAs was analyzed based on polarization curves, cyclic voltammograms and impedance spectroscopy data. Different testing conditions were investigated by varying the ammonia concentration from 0.1 to 1 M, the temperature from 25 °C to 60°C, and the KOH concentration from 0.1 to 5 M. References: [1] N. Morlanés et al., “A technological roadmap to the ammonia energy economy: Current state and missing technologies,” Chem. Eng. J., vol. 408, 2021, doi: 10.1016/j.cej.2020.127310. [2] N. M. Adli, H. Zhang, S. Mukherjee, and G. Wu, “Review—Ammonia Oxidation Electrocatalysis for Hydrogen Generation and Fuel Cells,” Journal of the Electrochemical Society, vol. 165, no. 15. pp. J3130–J3147, 2018, doi: 10.1149/2.0191815jes.
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Kusoglu, Ahmet. "(Invited) Electrochemical Characterization of Catalyst/Ionomer Interfaces". ECS Meeting Abstracts MA2023-02, n. 57 (22 dicembre 2023): 2747. http://dx.doi.org/10.1149/ma2023-02572747mtgabs.
Abstract (sommario):
Electrochemical energy conversion devices such as polymer-electrolyte fuel cells, water-splitting or carbon dioxide reduction electrolyzers, utilize ionically-conductive polymers (ionomers) in their electrode structure where an ionomer forms interfaces with the catalysts. The ionomers exist as nanometer-thick film to cover the catalyst particles and act as a binder while enabling the transport of active species necessary for the reactions. While the nature of species and operational environment differs across these devices, their overall efficiency and performance is influenced by the electrode architecture, where the interfaces and interactions between the ionomers and catalysts play an important role. In hydrogen technologies, for example, ionomer thin films bind the catalyst sites and carbon supports to facilitate transport of ionic (e.g. protons), liquid (water) and gaseous (e.g., oxygen) species under a nano-confined environment. Such confinement effects not only change the ionomer structure and properties, usually with a tendency to increase transport resistances, but also amplify the impact of the electrocatalyst-ionomer interactions in the electrodes, thereby reducing the catalyst activity. Thus, understanding the behavior of nano-confined ionomers and their interactions with the catalyst surfaces is key for mitigating the transport resistances in catalyst ionomers and improving the electrode performance and cell efficiency.This talk will provide insights into electrochemical characterization of catalyst ionomers by focusing on varying chemistries of perfluorosulfonated cation-exchange ionomers with additional examples of anion-exchange ionomers for emerging technologies. The hydration and transport properties of proton-exchange catalyst-ionomers will be examined with the effects of chemistry, processing and thickness (degree of confinement), along with their impact on the morphological changes governing the film function. Through a systematic variation of material chemistries and environmental parameters, primary factors impacting the structure-property relationship of catalyst ionomers are described along with a discussion of secondary factors altering the cation-anion interactions. Then, the interplay between the effects of chemistry and ion exchange (capacity) on modifying the transport function and the strength of ionomer-catalyst interactions will be presented. The results will be collated to elucidate the underlying origins of the transport resistances occurring in electrodes, and to develop materials and processing strategies for their mitigation for improved performance and efficiency in electrochemical energy devices.
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Moon, Ha-Neul, Hyeon-Bee Song e Moon-Sung Kang. "Thin Reinforced Ion-Exchange Membranes Containing Fluorine Moiety for All-Vanadium Redox Flow Battery". Membranes 11, n. 11 (11 novembre 2021): 867. http://dx.doi.org/10.3390/membranes11110867.
Abstract (sommario):
In this work, we developed pore-filled ion-exchange membranes (PFIEMs) fabricated for the application to an all-vanadium redox flow battery (VRFB) by filling a hydrocarbon-based ionomer containing a fluorine moiety into the pores of a porous polyethylene (PE) substrate having excellent physical and chemical stabilities. The prepared PFIEMs were shown to possess superior tensile strength (i.e., 136.6 MPa for anion-exchange membrane; 129.9 MPa for cation-exchange membrane) and lower electrical resistance compared with commercial membranes by employing a thin porous PE substrate as a reinforcing material. In addition, by introducing a fluorine moiety into the filling ionomer along with the use of the porous PE substrate, the oxidation stability of the PFIEMs could be greatly improved, and the permeability of vanadium ions could also be significantly reduced. As a result of the evaluation of the charge–discharge performance in the VRFB, it was revealed that the higher the fluorine content in the PFIEMs was, the higher the current efficiency was. Moreover, the voltage efficiency of the PFIEMs was shown to be higher than those of the commercial membranes due to the lower electrical resistance. Consequently, both of the pore-filled anion- and cation-exchange membranes showed superior charge–discharge performances in the VRFB compared with those of hydrocarbon-based commercial membranes.
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Narducci, Riccardo, Gianfranco Ercolani, Raul Andres Becerra-Arciniegas, Luca Pasquini, Philippe Knauth e Maria Luisa Di Vona. "“Intrinsic” Anion Exchange Polymers through the Dissociation of Strong Basic Groups: PPO with Grafted Bicyclic Guanidines". Membranes 9, n. 5 (29 aprile 2019): 57. http://dx.doi.org/10.3390/membranes9050057.
Abstract (sommario):
We synthesized anion exchange polymers by a reaction of chloromethylated poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) with strongly basic 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD). TBD contains secondary and tertiary amine groups in the guanidine portion. To favor the functionalization with the secondary amine, TBD was activated with butyl lithium. The yield of amine formation via the reaction of the benzyl chloride moiety with TBD was 85%. Furthermore, we prepared polymers with quaternary ammonium groups by the reaction of PPO-TBD with CH3I. The synthesis pathways and ionomer structure were investigated by NMR spectroscopy. The thermal decomposition of both ionomers, studied by thermogravimetry, started above 200 °C, corresponding to the loss of the basic group. The ion exchange capacities, water uptake and volumetric swelling are also reported. The “intrinsic” anion conductivity of PPO-TBD due to the dissociation of grafted TBD was in the order of 1 mS/cm (Cl form). The quaternized ionomer (PPO-TBD-Me) showed an even larger ionic conductivity, above 10 mS/cm at 80 °C in fully humidified conditions.
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Kim, Sungjun, Jiwoo Choi, Yung-Eun Sung, Mansoo Choi e Segeun Jang. "Fabrication of an Ionomer-Free Electrode Containing Vertically Aligned One-Dimensional Nanostructures for Alkaline Membrane Fuel Cells". Journal of The Electrochemical Society 168, n. 11 (1 novembre 2021): 114505. http://dx.doi.org/10.1149/1945-7111/ac3595.
Abstract (sommario):
An ionomer-free electrode containing vertically aligned one-dimensional nanostructures was designed and fabricated for anion exchange membrane fuel cells (AEMFCs) by hydrothermal and vapor deposition processes. The silver-coated zinc oxide (ZnO) nanorod arrays (diameter = ca. 100 nm) were directly aligned with the gas diffusion layer (GDL), and these one-dimensional structures of the electrode enhanced the mass transport of the reactants to the catalytic surface via its short diffusion pathway and ionomer-free nature. Applied as a cathode, the membrane electrode assembly (MEA) containing the vertically aligned gas diffusion electrode showed about 80% increased maximum power density than that of MEA containing a conventional electrode, which consisted of randomly dispersed carbon-supported nanoparticle catalysts and an ionomer. Moreover, the durability test revealed that the prepared ionomer-free catalyst layer was a more stable electrode than the conventional one. Also, water consumption and oxygen transport characteristics of AEMFC with the ionomer-free electrode at the cathode were intensively investigated by varying the electrode thickness and compositions.
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Xu, Jiahe, Johna Leddy e Carol Korzeniewski. "Cyclic Voltammetry as a Probe of Selective Ion Transport within Layered, Electrode-Supported Ion-Exchange Membrane Materials". Journal of The Electrochemical Society 169, n. 2 (1 febbraio 2022): 026520. http://dx.doi.org/10.1149/1945-7111/ac51fd.
Abstract (sommario):
Cyclic voltammetry was applied to investigate the permselective properties of electrode-supported ion-exchange polymer films intended for use in future molecular-scale spectroscopic studies of bipolar membranes. The ability of thin ionomer film assemblies to exclude mobile ions charged similarly to the polymer (co-ions) and accumulate ions charged opposite to the polymer (counterions) was scrutinized through use of the diffusible redox probe molecules [Ru(NH3)6]3+ and [IrCl6]2−. With the anion exchange membrane (AEM) phase supported on a carbon disk electrode, bipolar junctions formed by addition of a cation exchange membrane (CEM) overlayer demonstrated high selectivity toward redox ion extraction and exclusion. For junctions formed using a Fumion® AEM phase and a Nafion® overlayer, [IrCl6]2− ions exchanged into Fumion® prior to Nafion® overcoating remained entrapped and the Fumion® excluded [Ru(NH3)6]3+ ions for durability testing periods of more than 20 h under conditions of interest for eventual in situ spectral measurements. Experiments with the Sustainion® anion exchange ionomer uncovered evidence for [IrCl6]2− ion coordination to pendant imidazolium groups on the polymer. A cyclic voltammetric method for estimation of the effective diffusion coefficient and equilibrium extraction constant for redox active probe ions within inert, uniform density electrode-supported thin films was applied to examine charge transport mechanisms.
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Korchagin, Oleg, Vera Bogdanovskaya, Inna Vernigor, Marina Radina, Irina Stenina e Andrey Yaroslavtsev. "Development of Hydrogen–Oxygen Fuel Cells Based on Anion-Exchange Electrolytes and Catalysts with Reduced Platinum Content". Membranes 13, n. 7 (14 luglio 2023): 669. http://dx.doi.org/10.3390/membranes13070669.
Abstract (sommario):
Studies have been carried out to optimize the composition, formation technique and test conditions of membrane electrode assemblies (MEA) of hydrogen–oxygen anion-exchange membranes fuel cells (AEMFC), based on Fumatech anion-exchange membranes. A non-platinum catalytic system based on nitrogen-doped CNT (CNTN) was used in the cathode. PtMo/CNTN catalysts with a reduced content of platinum (10–12 wt.% Pt) were compared with 10 and 60 wt.% Pt/CNTN at the anode. According to the results of studies under model conditions, it was found that the PtMo/CNTN catalyst is significantly superior to the 10 and 60 wt.% Pt/CNTN catalyst in terms of activity in the hydrogen oxidation reaction based on the mass of platinum. The addition of the Fumion ionomer results in minor changes in the electrochemically active surface area and activity in the hydrogen oxidation reaction for each of the catalysts. In this case, the introduction of ionomer–Fumion leads to a partial blocking of the outer surface and the micropore surface, which is most pronounced in the case of the 60Pt/CNTN catalyst. This effect can cause a decrease in the characteristics of MEA AEMFC upon passing from 10PtMo/CNTN to 60Pt/CNTN in the anode active layer. The maximum power density of the optimized MEA based on 10PtMo/CNTN was 62 mW cm−2, which exceeds the literature data obtained under similar test conditions for MEA based on platinum cathode and anode catalysts and Fumatech membranes (41 mW cm−2). A new result of this work is the study of the effect of the ionomer (Fumion) on the characteristics of catalysts. It is shown that the synthesized 10PtMo/CNTN catalyst retains high activity in the presence of an ionomer under model conditions and in the MEA based on it.
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Yassin, Karam, Igal G. Rasin, Simon Brandon e Dario R. Dekel. "Which Properties Should Anion-Exchange Membranes Have to Achieve a Longer Fuel Cell Lifetime?" ECS Meeting Abstracts MA2022-02, n. 43 (9 ottobre 2022): 1607. http://dx.doi.org/10.1149/ma2022-02431607mtgabs.
Abstract (sommario):
The substantial advancements and availability of new cost-effective materials have drawn significant attention to the technology of anion-exchange membrane fuel cells (AEMFCs). The anion exchange membrane (AEM) is a core component in AEMFCs, essential for conducting hydroxide ions and, more importantly, controlling water transport between the fuel cell electrodes. In this contribution, we apply the computational methodology outlined in Refs. [1,2] to explore the effects of various membrane properties on AEMFC performance and its stability. We specifically consider the following parameters: (A) water diffusivity, (B) membrane thickness, (C) ion exchange capacity (IEC), (D) maximum hydration level (λmax) corresponding to ionomer/water contact (maximum number of water molecules per functional group), (E) hydroxide conductivity, and (F) degradation rate constant of the AEM functional group. First, we describe our modeling approach, which includes a one-dimensional isothermal and time-dependent model of AEMFC operations. The model considers the chemical degradation process of the ionomeric materials in the cell, transport phenomena through the anode and cathode gas diffusion layers, anode and cathode catalyst layers, and the membrane. Finally, the electrochemical reactions, hydrogen oxidation in the anode and oxygen reduction in the cathode, are described by Butler-Volmer kinetics. We present our main findings, demonstrating that membrane water diffusivity and λmax have the most significant impact on AEMFC lifetime, followed by membrane thickness and IEC, attributed to enhanced water distribution across the cell. We also demonstrate the significance of improving functional group stability to performance stability, while AEM hydroxide conductivity shows a negligible effect on AEMFC lifetime. Finally, we perform dimensional analysis and provide an analytical, useful correlation to estimate the AEMFC lifetime of selected membranes from the literature and compare it to the measured operation time. In conclusion, this work highlights important AEM parameters aimed at improving AEM designs in order to enhance the performance stability of AEMFCs. [1] D.R. Dekel, I.G. Rasin, S. Brandon, Predicting performance stability of anion exchange membrane fuel cells, J. Power Sources. 420 (2019) 118–123. https://doi.org/10.1016/j.jpowsour.2019.02.069. [2] K. Yassin, I.G. Rasin, S. Brandon, D.R. Dekel, Elucidating the role of anion-exchange ionomer conductivity within the cathode catalytic layer of anion-exchange membrane fuel cells, J. Power Sources. 524 (2022) 231083. https://doi.org/10.1016/j.jpowsour.2022.231083.
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Chae, Ji Eon, So Young Lee, Sung Jong Yoo, Jin Young Kim, Jong Hyun Jang, Hee-Young Park, Hyun Seo Park et al. "Polystyrene-Based Hydroxide-Ion-Conducting Ionomer: Binder Characteristics and Performance in Anion-Exchange Membrane Fuel Cells". Polymers 13, n. 5 (25 febbraio 2021): 690. http://dx.doi.org/10.3390/polym13050690.
Abstract (sommario):
Polystyrene-based polymers with variable molecular weights are prepared by radical polymerization of styrene. Polystyrene is grafted with bromo-alkyl chains of different lengths through Friedel–Crafts acylation and quaternized to afford a series of hydroxide-ion-conducting ionomers for the catalyst binder for the membrane electrode assembly in anion-exchange membrane fuel cells (AEMFCs). Structural analyses reveal that the molecular weight of the polystyrene backbone ranges from 10,000 to 63,000 g mol−1, while the ion exchange capacity of quaternary-ammonium-group-bearing ionomers ranges from 1.44 to 1.74 mmol g−1. The performance of AEMFCs constructed using the prepared electrode ionomers is affected by several ionomer properties, and a maximal power density of 407 mW cm−2 and a durability exceeding that of a reference cell with a commercially available ionomer are achieved under optimal conditions. Thus, the developed approach is concluded to be well suited for the fabrication of next-generation electrode ionomers for high-performance AEMFCs.
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López-Fernández, E., C. Gómez-Sacedón, J. Gil-Rostra, J. P. Espinós, A. R. González-Elipe, F. Yubero e A. de Lucas-Consuegra. "Ionomer-Free Nickel-Iron bimetallic electrodes for efficient anion exchange membrane water electrolysis". Chemical Engineering Journal 433 (aprile 2022): 133774. http://dx.doi.org/10.1016/j.cej.2021.133774.
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Faid, Alaa Y., Lin Xie, Alejandro Oyarce Barnett, Frode Seland, Donald Kirk e Svein Sunde. "Effect of anion exchange ionomer content on electrode performance in AEM water electrolysis". International Journal of Hydrogen Energy 45, n. 53 (ottobre 2020): 28272–84. http://dx.doi.org/10.1016/j.ijhydene.2020.07.202.
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Yu, Eileen Hao, Richard Burkitt, Xu Wang e Keith Scott. "Application of anion exchange ionomer for oxygen reduction catalysts in microbial fuel cells". Electrochemistry Communications 21 (luglio 2012): 30–35. http://dx.doi.org/10.1016/j.elecom.2012.05.011.
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Herring, Andrew M., Nora Catherine Buggy, Ivy Wu, Mei-Chen Kuo, Morgan Ezell, Kaylee Beiler, Andrew Johnson e Kevin Dunn. "(Invited) Controlling Charge Transfer and Ion Transport in Electrodes for the Oxygen Evolution Reaction". ECS Meeting Abstracts MA2022-02, n. 57 (9 ottobre 2022): 2170. http://dx.doi.org/10.1149/ma2022-02572170mtgabs.
Abstract (sommario):
Anion Exchange Membrane (AEM) based energy conversion devices offer the possibility of utilizing non-precious metals as the catalyst and the advantage of more facile electrochemical conversions. While many AEMs are showing practical performance and durability’s, their potential will only be realized if the catalyst particles are modulated by the cationic ionomer for maximum performance. The catalyst layer in the electrode provides the triple-phase boundary between the anion-conducting polymer, supported catalyst particles, and reactants where the electrochemical reactions take place. In proton-exchange membrane fuel cells (PEMFC), the electrode catalyst layer was developed empirically over many decades. State of the art AEM devices could be developed with new scientific insight and methodology facilitating the opportunity to be much more quickly developed as well as to exhibit maximum performance and durability. Also for PEMFC to improve Pt catalyst utilization, high surface area carbon-supported Pt catalysts were developed, followed by the development of catalyst inks and the implementation of electrode spraying techniques commonly in use today. However, carbon supported catalysts do not have the necessary durability for the oxygen evolution reaction (OER) necessitating the use of Iridium oxide in acid systems. We hypothesize that the crucial component of an electrode is the ionomer that modulates the transport of ions and neutrals to the catalyst surface and by its interaction with the surface of the catalyst can also modulates charge transfer in solid state electrodes. So, by understanding the ionomer chemistry we can design ionomer catalyst interfaces for maximum performance. For the OER we use porous Ni electrodes that we imbibe with catalyst ionomer inks. In these inks we can not only vary the catalyst to ionomer ratio, but the ionomer chemistry and IEC. To date we have studied nano-structured silver1 or cobalt oxide catalysts. The ionomers are either random or block co-polymers consisting of polyisoprene or polycyclooctene hydrophobic components as the hydrophobic component that can be hydrogenated to polymethylbutylene or polyethylene. The other component is a quaternizable polychlorostyrene that can we functionalize with trimethyl amine or methylpyrolidine. These combinations give a large experimental space in which to probe the effect of ionomer chemistry on electrode performance. We test the electrodes in a separated anode experiment where linear sweep voltammetry is used to get kinetic information and cyclic voltammetry is used to determine the double layer capacity that we use as a measure of electrochemical surface area. Using silver the ionomer chemistry clearly effcts charge transfer and transport of ions and neutrals in the electrode.1 Optimized electrodes are them used to construct 5 cm2 electrolysis cells where the electrolyzer performance and durability is evaluated. In these cells we use a Pt on carbon anode with a cationic ionomer of fixed composition and high performance triblock AEM2 that we developed that is currently being commercialized under license to SparkIonix as Tuffbrane™. Our studies to date use pumped carbonate as the water source, but we are also extending this work to distilled water or hydroxide solutions. Removing the supporting anions from the water feed by ionomer/catalyst interface engineering would dramatically improve these AEM based water electrolysis systems. “Evaluating the Effect of Ionomer Chemical Composition in Silver-Ionomer Catalyst Inks toward the Oxygen Evolution Reaction by Half-Cell Measurements and Water Electrolysis.” N.C. Buggy, I. Wu, Y. Du, R. Ghosh, M.-C. Kuo, M.S. Ezell, J.M. Crawford, S. Seifert, M.A. Carreon, E.B. Coughlin, A.M. Herring,* Electrochimica Acta., 2022, 412, 140124. “A Polyethylene-based Triblock Copolymer Anion Exchange Membrane with High Conductivity and Practical Mechanical Properties.” N.C. Buggy, Y. Du, M.-C. Kuo, K.A. Ahrens,S. Wilkinson, S. Seifert, E.B. Coughlin,* and A.M. Herring*, ACS Applied Polymer Materials, 2020, 2, 1294 – 1303.