Using distribution of relaxation times to separate the impedances in the membrane electrode assembly for high-temperature polymer electrolyte membrane fuel cells

In the membrane electrode assembly (MEA) of high-temperature polymer electrolyte membrane fuel cells (HT-PEMFCs), many types of resistance existed, but they have not been distinctly characterized in previous research. In this study, the distribution of relaxation times (DRT) methodology is employed, in conjunction with a home-built electrochemical electrode analysis system (EEAS), to figure out the specific resistance components in the cathode gas diffusion electrode (GDE). The impedance analysis by the DRT method was conducted using the electrochemical impedance spectrum obtained at different temperatures and current densities of the cathode only, isolated from the MEA environment. The four peaks (designated as Peak 0 to 3) were depicted at DRT plots of cathode GDE below 10 3 Hz. By comparing the DRT plots for different conditions and considering the EEAS structure, the four peaks were explained to be caused by distinct resistances occurring at the electrode and interface. The regions of each peak were distinguished according to their position changes with temperature and current density. Furthermore, by contrasting the DRT plots of the cathode GDE with those of MEA containing the same cathode, an additional peak (referred to as Peak 4) is identified between 10 3 Hz and 10 4 Hz, which was attributed to resistance originating from the anode. This study could provide a new approach for future research of new catalysts and electrodes utilizing the resistance analysis of MEA for HT-PEMFC. • The EEAS was utilized to perform electrochemical analysis of the GDE. • DRT method separates resistances as peaks in the cathode GDE of HT-PEMFCs. • Each peak from the DRT plot is assigned according to the origin of resistance. • Comparative study with MEA differentiates the resistance from electrodes.