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[Display omitted] • Ionic liquid (IL)-adsorbed catalyst changes the morphology of the catalyst layer. • IL adsorption reduces the ORR charge transfer resistance in the electrode. • IL adsorption enhances the stability under the accelerated durability test. A majority of studies focus on developing oxygen reduction reaction (ORR) catalysts and cathode configurations to enhance the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs). In this study, resistance analyses of the membrane electrode assembly (MEA) are conducted to elaborate on the performance and durability improvements induced by the adsorption of [MTBD][beti] ionic liquid (IL) on the commercial PtCo/C catalyst. The morphological changes caused by IL adsorption are observed on micro and macro scales via physicochemical methods. From the half-cell measurement, when the 4 wt% IL was adsorbed, a 15 mV improvement in ORR activity occurred, and as the adsorption amount increased, the activity decreased. The MEA using 8 wt% IL adsorbed catalyst outperforms 1.7 times higher current density at 0.8 V and 40 % lower charge transfer resistance. Distribution of relaxation time resistance analysis reveals that oxygen mass transfer resistance (R mass), ORR charge transfer resistance (R ORR), and proton charge transfer resistance (R proton) decrease due to IL adsorption. During accelerated durability tests, IL 8 % MEA showed a 58 % increase in durability, and a lower degradation of R ORR and R proton encouraged improved durability. The resistance analyses in this study contribute to identifying the factors responsible for the performance and durability enhancement of PEMFC. [ABSTRACT FROM AUTHOR]

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 103 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 103 Hz and 104 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. [Display omitted] • 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. [ABSTRACT FROM AUTHOR]

Four commercial gas diffusion layers (GDLs) are applied to high-temperature polymer electrolyte fuel cell anodes to investigate the relationship between microporous layer (MPL) properties and the performance of membrane electrode assembly. Subsequently, the physical properties such as the crack area and porosity of the MPL are analyzed via various methods. It is found that the capillary pressure of phosphoric acid (PA) from several theories is inversely related to the mass transfer capability (MTC) of the MPL. Finally, a new transport property named PA MTC of the MPL is proposed using the PA capillary pressure and MTC in MPL. The results indicate that the voltage at both low and high current densities increases separately as the PA MTC in the MPL adjusts to 0.5 MPa mm-1. Subsequently, the voltage beyond 0.5 MPa mm-1 increases in low current density contrary to the voltage at a high current density. • Anode GDLs are applied to high-temperature polymer electrolyte fuel cell. • The crack area of MPL has a high correlation with its porosity. • A new transport property called PA MTC in the MPL is proposed. [ABSTRACT FROM AUTHOR]