Experiments and Molecular Dynamics Simulations Study on the Effect of Drying Temperature for PEMFC Catalyst Layer

The drying temperature (50–90 °C) critically impacts proton exchange membrane fuel cell catalyst layer (CL) microstructure and performance. Increasing the temperature from 50 to 90 °C enlarges the average pore size from 21.4 to 45.1 nm, significantly enhancing Knudsen diffusion and promoting macropore formation for improved molecular diffusion. Molecular dynamics simulations reveal that temperature influence the solvent evaporation rate by modulating ionomer chain conformations. Lower drying temperatures yield a more homogeneous ionomer film on the catalyst surface but reduce oxygen solubility within it. These CLs also exhibit a higher electrochemically active surface area (ECSA) and better proton conduction. An optimal balance between oxygen solubility and diffusion in the ionomer film is achieved at 70 °C. Consequently, electrochemical testing shows the 70 °C-dried CL delivers peak performance with a power density of 0.64 W cm⁻². This is 5.53% and 12.77% higher than CLs dried at 50 °C and 90 °C, respectively. This study elucidates the correlation between drying temperature, solvent evaporation, microstructure, and performance.