Insights into the effect of drying temperature on catalyst layer structure and PEM water electrolysis performance

The drying process of the membrane electrode assembly (MEA) has a significant impact on the structure of catalyst layer (CL) and the performance of proton exchange membrane water electrolysis (PEMWE). However, there is a lack of research on the relationship between drying temperature, CL structure, and performance. In this study, we investigated the drying process to regulate the CL microstructure, and the relationship between CL structure and water electrolysis performance was confirmed. As the drying temperature increased from 70 degrees C to 110 degrees C, the morphology of the CL changed from dense to loose due to differences in solvent evaporation rate. Specifically, the pore volume fractions of the CL (Vvoid) increased from approximately 0 to 27%. Electrochemical tests revealed that the dense CL structure formed at lower drying temperatures increased activation and mass transfer losses, while the aggregated CL structure formed at higher drying temperatures resulted in high ohmic loss. Consequently, the MEA dried at 90 degrees C exhibited the best water electrolysis performance, achieving a voltage of 1.78V at a current density of 2.0 A cm-2. The Vvoid was found to 18%, while the wet ionomer volume fraction (Vion,wet) was 50%. Furthermore, the durability test demonstrated that the MEA dried at 90 degrees C exhibited a voltage rate of-25 mu V h-1 after 200 h of continuous current operation. The stable cell voltage was still observed even after 1000 intermittent start-stop operations, indicating excellent durability. This study provides valuable in-sights for optimizing the preparation process of MEA to enhance the structure of the CL and improve the PEMWE. It also presents a viable approach towards the commercialization of PEMWE.