Carbon mesopore depth engineering boosts the performance of low-platinum fuel cells

Ionomer adsorption-induced Pt poisoning and high local oxygen transport resistance constitute two critical challenges preventing proton exchange membrane fuel cells from achieving low-Pt loadings. Yet, strategies concurrently mitigating both issues remain limited, making it challenging to achieve satisfactory performance in both kinetically controlled low-current-density and mass transport-controlled high-current-density regions. Herein, we show that this limitation can be addressed with a mesoporous carbon support design whose key lies in constructing a small mesopore-dominated structure while rationally controlling pore depth to a medium level. This design creates an ideal local reaction environment for Pt nanoparticles inside the mesopores, one that protects most Pt from ionomer poisoning while achieving efficient oxygen diffusion. Using the developed carbon support, we synthesize an intermetallic PtCo nanocatalyst that delivers competitive membrane electrode assembly performance at low-Pt cathode loading (0.1 mg_Pt cm^-2), with a H₂-air rated power density of 1.23 W cm^-2 at 0.67 V under heat-rejection-constrained conditions and a H₂-O₂ mass activity of 1.1 A mg_Pt^-1.