Numerical Analysis of Silica Coating Effect on Pt Cathode Catalyst in Polymer Electrolyte Fuel Cells

Abstract

In order to accelerate the development of polymer electrolyte fuel cells (PEFCs), it is important to optimize the structure of catalyst layers (CLs) including Pt particles, ionomer loading, and porosity, resulting in the improvement of performance. Numerical analysis can assist in designing the optimized CLs without trial and error. In this study, the effects of silica-coated Pt catalysts (SiO2/Pt/C) were investigated by experimental measurements and numerical analysis in order to obtain manufacturing guidelines by designing optimized CLs for PEFCs. In the experimental results, the SiO2/Pt/C showed lower performance than non-coated Pt catalysts (Pt/C) under relative humidity (RH) of 80% at 80°C. In the case of the SiO2/Pt/C, the addition of two parameters including the enhancement of proton conductivity and an increase in the oxygen diffusion resistance in the CLs, attributed to silica layers, were considered. The distribution of current density at 0.8 A cm−2 of the SiO2/Pt/C at each humidity condition (100%RH, 80%RH, 60%RH, 40%RH) is more homogeneous and reached closer to the gas diffusion layer compared to those of the Pt/C. The result indicates that it is possible to improve durability by increasing the reaction located near the polymer electrolyte membrane. For both catalysts, the overvoltages at 0.8 A cm−2 were similar to each other, except for that of proton resistance in ionomer and oxygen diffusion in the ionomer.