Identifying ideal solvents through evaluating mass transport channels at local three-phase interfaces of Pt/C catalysts: MD simulations.

The performance of proton exchange membrane fuel cells (PEMFCs) is defined by the three-phase interface within their core membrane electrode assembly. However, the solvent-dependent distribution of Nafion ionomers and its impact on oxygen transport and Pt utilization at the Pt/Nafion interface remain insufficiently understood. In this work, classical molecular dynamics simulations were employed to systematically investigate how eight commonly used solvents (water, acetone, butanol, ethanol, ether, isopropanol, methanol, and propanol) regulate the local three-phase interface structure within the cathode catalyst layer. The effects of solvents on Nafion ionomer aggregation, interfacial microporosity, oxygen diffusion channels, and the accessibility of Pt active sites were quantitatively analyzed. The results reveal that Nafion ionomers exhibit pronounced aggregation in water, whereas a highly uniform interfacial distribution is achieved in ether. Notably, isopropanol enables a well-balanced interfacial microenvironment, delivering a peak oxygen flux exceeding 0.25 mol·cm-2·s-1 while avoiding excessive occupation of Pt active sites by sulfonate groups. By jointly considering proton transport channels, gas-liquid transport channels, and site blocking effects, isopropanol is identified as the optimal solvent, yielding the highest Pt utilization of 32.1%. The findings offer molecular-level insights that enable rational solvent selection and catalyst layer optimization for high-efficiency PEMFCs.