Revealing local oxygen transport in ionomer films on multidimensional nanoscale catalysts in fuel cells

Abstract

State-of-the-art multidimensional catalysts have been developed to realize high-performance proton exchange membrane fuel cells (PEMFCs). However, local oxygen transport resistance significantly limits the catalytic performance of catalysts in actual PEMFC application. Therefore, we comprehensively investigated the ionomer film morphologies and local oxygen transport mechanisms near representative multidimensional catalysts with various structures to reveal the effect of catalyst structures on local oxygen transport. We demonstrate that the one-dimensional nanowire structure of catalysts shows a much lower local oxygen transport resistance than three-dimensional ones owing to broader and shorter oxygen transport paths in well-layered ionomer films on one-dimensional catalysts. Moreover, the core–shell and hollow structures of catalysts achieve local oxygen transport capacity identical to the solid one while greatly reducing platinum usage. Therefore, the one-dimensional core–shell or hollow structures of catalysts can highly reduce local oxygen transport resistance in PEMFCs with low platinum usage. The findings are valuable for catalyst designs to achieve low local oxygen transport in actual PEMFC application.