Numerical simulation of gradient catalyst layer design in proton exchange membrane water electrolyzer with enhanced performance

The catalyst loading, ionomer content and agglomerate radius in the catalyst layer (CL) of proton exchange membrane water electrolyzer (PEMWE) plays critical role on its electrochemical performance. Conventionally, the CL in PEMWE is modeled with uniform composition and homogeneous domain. In this study, a two-dimensional PEMWE model considering linear gradient distribution of catalyst, ionomer and agglomerate radius in CL was developed and their effect on the electrolyzer performance were systematically investigated. The results show that, when the total catalyst, ionomer loading and the average agglomerate radius in CL are kept constant, the optimum PEMWE performance was achieved with low catalyst loading, high ionomer content, and small agglomerates radius distribution at the CL-PEM interface. Compared with the uniform CL, this optimized gradient CL design results into a 7.01% improvement in the PEMWE current density. Meanwhile, under the gradient CL design, increased maximum temperature and oxygen concentration with lower liquid water saturation is found inside PEMWE, which might affect the temperature distribution uniformity within the PEMWE. The results of this work provide insightful guidance for the CL optimization design of PEMWE.