Jang, Jong Hyun Jeon, Sunyeol Cho, Jae Hyung Kim, Soo-Kil Lee, Sang-Yeop Cho, EunAe Kim, Hyung-Juhn Han, Jonghee Lim, Tae-Hoon 2024-01-20T20:31:45Z 2024-01-20T20:31:45Z 2021-09-03 2009-11 0013-4651 https://pubs.kist.re.kr/handle/201004/132018 For polymer electrolyte membrane fuel cell (PEMFC) and direct methanol fuel cell (DMFC) catalyst layers (CLs), a complex capacitance analysis of impedance data was developed to evaluate the catalyst/ionomer interfacial capacitance and ionic resistance of ionomer networks without nonlinear data fitting. First, assuming no faradaic reactions, equivalent circuits for the CLs were suggested, which are similar to electric double-layer capacitor systems with porous carbon electrodes. Then, with the simulated complex capacitances, it was confirmed that the plots of the real and imaginary parts as a function of ac frequency are determined by the catalyst/ionomer interfacial capacitances and the ionic resistances time constants, which are important characteristics for high fuel cell performances. Experimentally, the condition of no faradaic reactions was realized by supplying nitrogen or water to the cathodes instead of air and by fixing the dc potential at 0.4 V during the impedance measurements. By performing a complex capacitance analysis, the interfacial capacitances and ionic resistances of PEMFC membrane electrode assemblies (MEAs) can be obtained at various relative humidities, proving that the catalytic activity in fuel cell operation depends on ionic resistances as well as on the catalyst/ionomer interfacial area. The effects of various MEA preparation methods on the ionomer distributions and DMFC performances were analyzed by a complex capacitance analysis. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3187928] All rights reserved. English ELECTROCHEMICAL SOC INC ELECTROLYTE FUEL-CELLS ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY GAS-DIFFUSION ELECTRODES PORE-SIZE DISTRIBUTION AC-IMPEDANCE POROUS-ELECTRODES CONDUCTIVITY PROFILES AGGLOMERATE MODEL PERFORMANCE CATHODE Complex Capacitance Analysis of Ionic Resistance and Interfacial Capacitance in PEMFC and DMFC Catalyst Layers Article 10.1149/1.3187928 1 JOURNAL OF THE ELECTROCHEMICAL SOCIETY, v.156, no.11, pp.B1293 - B1300 JOURNAL OF THE ELECTROCHEMICAL SOCIETY 156 11 B1293 B1300 scie scopus 000270457600020 2-s2.0-70349751759 Electrochemistry Materials Science, Coatings & Films Electrochemistry Materials Science Article ELECTROLYTE FUEL-CELLS ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY GAS-DIFFUSION ELECTRODES PORE-SIZE DISTRIBUTION AC-IMPEDANCE POROUS-ELECTRODES CONDUCTIVITY PROFILES AGGLOMERATE MODEL PERFORMANCE CATHODE