Enhancement of oxygen transport in the catalyst layer of proton exchange membrane fuel cell via heat treatment

Lowering the Pt loading would decrease proton exchange membrane fuel cell (PEMFC) cost, but inevitably increase local oxygen transport resistance and cause performance loss at high current densities. To enhance the local oxygen transport within the catalyst layer, the heat treatment method of the electrode is proposed to regulate ionomer microstructure. After heat-treating the electrode over the ionomer glass-transition temperature, the local oxygen transport resistance decreases and the limiting current density enlarges, which in turn improves the cell performance at high current densities, confirming the enhancement of oxygen transport. Based on the AFM and contact angle test results of thin-film ionomers, it can be further confirmed that the phase-separation within thin-film ionomers is enhanced after heat treatment that builds more oxygen transport pathways inside the ionomer. This work offers a simple and effective method to enhance the local oxygen transport process and is beneficial for future high performance PEMFC development.