Pt Active\nSite Density Optimization of the Catalyst\nLayer for an Ultralow-Pt-Loading PEMFC

As a power generation device with high efficiency and\nlow pollution,\nthe proton exchange membrane fuel cell (PEMFC) has the potential to\nbecome important energy conversion equipment. Drastically reducing\nthe Pt usage in the catalyst layer (CL) can bring great cost benefits\nto the PEMFC, whereas it leads to polarization loss caused by the\nlocal transport process with the limitation of a reduced Pt loading.\nHerein, local oxygen transport loss was mitigated by reducing the\ncatalyst mass fraction to adjust the Pt active site density in the\nCL. A membrane electrode assembly (MEA) with a drastically reduced\nPt loading of 0.05 mg<sub>Pt</sub> cm<sup>–2</sup> was synthesized,\nachieving a maximum mass power density of 12.8 W mg<sub>Pt</sub><sup>–1</sup>. Ultralow-Pt MEAs with CL thickness in proportional\nvariation were prepared to precisely control the cathode Pt active\nsite density. It was found that a cathode CL with moderate Pt active\nsite density is conducive to oxygen transport resistance reduction\nand performance display. This study lays the foundation for designing\nand utilizing ultralow-Pt MEA for PEMFC applications.