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Kim YS. Hydrocarbon Ionomeric Binders for Fuel Cells and Electrolyzers. ADVANCED SCIENCE (WEINHEIM, BADEN-WURTTEMBERG, GERMANY) 2023; 10:e2303914. [PMID: 37814366 DOI: 10.1002/advs.202303914] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2023] [Revised: 08/08/2023] [Indexed: 10/11/2023]
Abstract
Ionomeric binders in catalyst layers, abbreviated as ionomers, play an essential role in the performance of polymer-electrolyte membrane fuel cells and electrolyzers. Due to environmental issues associated with perfluoroalkyl substances, alternative hydrocarbon ionomers have drawn substantial attention over the past few years. This review surveys literature to discuss ionomer requirements for the electrodes of fuel cells and electrolyzers, highlighting design principles of hydrocarbon ionomers to guide the development of advanced hydrocarbon ionomers.
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Affiliation(s)
- Yu Seung Kim
- MPA-11: Materials Synthesis and Integrated Devices, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
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Olbrich W, Kadyk T, Sauter U, Eikerling M, Gostick J. Structure and conductivity of ionomer in PEM fuel cell catalyst layers: a model-based analysis. Sci Rep 2023; 13:14127. [PMID: 37644035 PMCID: PMC10465542 DOI: 10.1038/s41598-023-40637-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2023] [Accepted: 08/11/2023] [Indexed: 08/31/2023] Open
Abstract
Efforts in design and optimization of catalyst layers for polymer electrolyte fuel cells hinge on mathematical models that link electrode composition and microstructure with effective physico-chemical properties. A pivotal property of these layers and the focus of this work is the proton conductivity, which is largely determined by the morphology of the ionomer. However, available relations between catalyst layer composition and proton conductivity are often adopted from general theories for random heterogeneous media and ignore specific features of the microstructure, e.g., agglomerates, film-like structures, or the hierarchical porous network. To establish a comprehensive understanding of the peculiar structure-property relations, we generated synthetic volumetric images of the catalyst layer microstructure. In a mesoscopic volume element, we modeled the electrolyte phase and calculated the proton conductivity using numerical tools. Varying the ionomer morphology in terms of ionomer film coverage and thickness revealed two limiting cases: the ionomer can either form a thin film with high coverage on the catalyst agglomerates; or the ionomer exists as voluminous chunks that connect across the inter-agglomerate space. Both cases were modeled analytically, adapting relations from percolation theory. Based on the simulated data, a novel relation is proposed, which links the catalyst layer microstructure to the proton conductivity over a wide range of morphologies. The presented analytical approach is a versatile tool for the interpretation of experimental trends and it provides valuable guidance for catalyst layer design. The proposed model was used to analyze the formation of the catalyst layer microstructure during the ink stage. A parameter study of the initial ionomer film thickness and the ionomer dispersion parameter revealed that the ionomer morphology should be tweaked towards well-defined films with high coverage of catalyst agglomerates. These implications match current efforts in the experimental literature and they may thus provide direction in electrode materials research for polymer electrolyte fuel cells.
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Affiliation(s)
- W Olbrich
- Theory and Computation of Energy Materials (IEK-13), Institute of Energy and Climate Research, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany.
- Robert Bosch GmbH, Corporate Research, 71272, Renningen, Germany.
- Chair of Theory and Computation of Energy Materials, Faculty of Georesources and Materials Engineering, RWTH Aachen University, 52062, Aachen, Germany.
| | - T Kadyk
- Theory and Computation of Energy Materials (IEK-13), Institute of Energy and Climate Research, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
- Jülich Aachen Research Alliance, JARA Energy, 52425, Jülich, Germany
| | - U Sauter
- Robert Bosch GmbH, Corporate Research, 71272, Renningen, Germany
| | - M Eikerling
- Theory and Computation of Energy Materials (IEK-13), Institute of Energy and Climate Research, Forschungszentrum Jülich GmbH, 52425, Jülich, Germany
- Chair of Theory and Computation of Energy Materials, Faculty of Georesources and Materials Engineering, RWTH Aachen University, 52062, Aachen, Germany
- Jülich Aachen Research Alliance, JARA Energy, 52425, Jülich, Germany
| | - J Gostick
- Department of Chemical Engineering, University of Waterloo, Waterloo, ON, Canada
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Olbrich W, Kadyk T, Sauter U, Eikerling M. Modeling of wetting phenomena in cathode catalyst layers for PEM fuel cells. Electrochim Acta 2022. [DOI: 10.1016/j.electacta.2022.140850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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Yeon JH, Jang Y, Choi M, Jang S. Layer-by-Layer Polydimethylsiloxane Modification Using a Two-Nozzle Spray Process for High Durability of the Cathode Catalyst in Proton-Exchange Membrane Fuel Cells. ACS APPLIED MATERIALS & INTERFACES 2021; 13:56014-56024. [PMID: 34783545 DOI: 10.1021/acsami.1c12616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
The catalyst layer's high durability is essential in commercializing polymer electrolyte membrane fuel cells (PEMFCs), particularly for vehicle applications, because their frequent on/off operation can induce carbon corrosion, which affects surface properties and morphological characteristics of the carbon and results in aggregation and detachment of Pt nanoparticles on the carbon surface. Herein, to address the carbon corrosion problem while delivering a high-performance PEMFC, polydimethylsiloxane (PDMS) with high gas permeability, chemical stability, and hydrophobicity was employed to protect the catalyst layer from carbon corrosion and improve the mass transport. Because the catalyst slurry using alcohol-based solvents showed low compatibility with nonpolar solvents of the PDMS solution, a parallel two-nozzle system with separated solution reservoirs was developed by modifying a conventional three-dimensional printing machine. To determine the optimal PDMS amount in the cathode catalyst layer, PDMS solution concentration was varied by quantitatively controlling the PDMS amount coated on the electrode layer. Finally, the PEMFC with the PDMS-modified cathode of 0.1 mgPDMS cm-2 loading showed enhanced durability due to increased electrochemical surface and maximum power density by 37.2 and 21.7%, respectively, after the accelerated stress test. Furthermore, an improvement in the initial performance from enhanced water management was observed compared to those of PEMFCs with a conventional electrode.
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Affiliation(s)
- Je Hyeon Yeon
- Global Frontier Center for Multiscale Energy Systems, Seoul National University, Seoul 08826, Republic of Korea
- Department of Mechanical Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Yeonghwan Jang
- School of Mechanical Engineering, Kookmin University, Seoul 02707, Republic of Korea
| | - Mansoo Choi
- Global Frontier Center for Multiscale Energy Systems, Seoul National University, Seoul 08826, Republic of Korea
- Department of Mechanical Engineering, Seoul National University, Seoul 08826, Republic of Korea
| | - Segeun Jang
- School of Mechanical Engineering, Kookmin University, Seoul 02707, Republic of Korea
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Harada M, Takata SI, Iwase H, Kajiya S, Kadoura H, Kanaya T. Distinguishing Adsorbed and Deposited Ionomers in the Catalyst Layer of Polymer Electrolyte Fuel Cells Using Contrast-Variation Small-Angle Neutron Scattering. ACS OMEGA 2021; 6:15257-15263. [PMID: 34151104 PMCID: PMC8210452 DOI: 10.1021/acsomega.1c01535] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Accepted: 05/14/2021] [Indexed: 06/13/2023]
Abstract
The ionomers distributed on carbon particles in the catalyst layer of polymer electrolyte fuel cells (PEFCs) govern electrical power via proton transport and oxygen permeation to active platinum. Thus, ionomer distribution is a key to PEFC performance. This distribution is characterized by ionomer adsorption and deposition onto carbon during the catalyst-ink coating process; however, the adsorbed and deposited ionomers cannot easily be distinguished in the catalyst layer. Therefore, we identified these two types of ionomers based on the positional correlation between the ionomer and carbon particles. The cross-correlation function for the catalyst layer was obtained by small-angle neutron scattering measurements with varying contrast. From fitting with a model for a fractal aggregate of polydisperse core-shell spheres, we determined the adsorbed-ionomer thickness on the carbon particle to be 51 Å and the deposited-ionomer amount for the total ionomer to be 50%. Our technique for ionomer differentiation can be used to optimally design PEFC catalyst layers.
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Affiliation(s)
- Masashi Harada
- Toyota
Central R&D Labs., Inc., Nagakute, Aichi 480-1192, Japan
| | - Shin-ichi Takata
- J-PARC
Center, Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195, Japan
| | - Hiroki Iwase
- Neutron
Science and Technology Center, Comprehensive
Research Organization for Science and Society (CROSS), Tokai, Ibaraki 319-1106, Japan
| | - Shuji Kajiya
- Toyota
Central R&D Labs., Inc., Nagakute, Aichi 480-1192, Japan
| | - Hiroaki Kadoura
- Toyota
Central R&D Labs., Inc., Nagakute, Aichi 480-1192, Japan
| | - Toshiji Kanaya
- Institute
of Materials Structure Science, High Energy Accelerator Research Organization, Tokai, Ibaraki 319-1106, Japan
- Materials
and Life Science Division, J-PARC Center, Tokai, Ibaraki 319-1106, Japan
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