Insights into properties of non-precious metal catalyst (NPMC)-based catalyst layer for proton exchange membrane fuel cells

Non-precious metal catalysts (NPMCs) are regarded as the ultimate alternative to high-cost Pt-based catalysts for oxygen reduction reaction in proton exchange membrane fuel cells (PEMFCs). Indeed, great progresses have been made in the rotating disk electrode (RDE) performance of NPMCs, while their corresponding fuel cell performance remains far from satisfying real demands due to the fact that the properties of NPMC-based electrode need to be clarified and optimized. In this work, a series of properties including the oxygen reduction activities, catalyst layer proton conduction resistance and oxygen transport resistance are investigated on membrane electrode assemblies (MEAs) fabricated from home-made Fe-N-C catalysts. It is found that both the oxygen reduction activities and catalyst layer proton conduction increase with the catalyst loading. Unexpectedly, the total oxygen transport resistance is quite large for the MEA with a lower catalyst loading, and the resistance first decreases and then enlarges with the increase in catalyst loading, resulting from a comprehensive effect between local transport and bulk transport. This provides a novel meaningful guide that compared to using Pt-based MEA technique directly, special and deliberate designs are needed for MEAs based on NPMCs to balance the cathode catalyst layer (CCL) activity, proton resistance and oxygen transport resistance simultaneously.

Automated summary

The study reveals that the performance of non-precious metal catalysts needs to find a balance between oxygen reduction activity, proton conduction resistance, and oxygen transport resistance, requiring careful and deliberate designs for MEAs based on NPMCs.