Hierarchical catalyst layer structure for enhancing local oxygen transport in low Pt proton exchange membrane fuel cells

As the platinum loading in the cathode of proton exchange membrane fuel cells (PEMFCs) continues to decrease, a challenging issue arises, i.e., the sudden increase in local oxygen transport resistance in the cathode catalyst layer (CCL). Herein, we have devised a hierarchical CL structure to regulate the ionomer distribution in order to enhance local oxygen transport process. Initially, the catalyst layer is fabricated utilizing markedly low I/C inks, followed by drop-casting of the remaining requisite ionomer which facilitates the natural infiltration of ionomer into the pore structure. The infiltrated ionomer forms the mainstem proton conducting structure, while the ionomer already presents in the ink created tributary proton conducting pathways, resulting in a hierarchical structure and reduced ionomer film covered on catalysts surface. As a result, local oxygen transport is enhanced with a 59.1% reduction in transport resistance and the peak power density increases by 43.52%.