Catalytic synergy of PtCo alloy nanoparticles anchored on S, P-doped hierarchical carbon nitrides for efficient and durable oxygen reduction in high-temperature PEMFCs

Intensified electrochemical corrosion under high-temperature and phosphoric acid conditions poses a significant challenge to the catalysts in high-temperature proton exchange membrane fuel cells (HT-PEMFCs). Herein, a S, P-doped hierarchical porous carbon nitride (S, P-HCN) supported PtCo alloy catalyst was developed to address this issue. The multilayered porous structure of S, P-HCN ensures high metal dispersion, a large specific surface area, and enhanced mass transfer. The PtCo/S, P-HCN catalyst exhibits remarkable performance, with specific activity (1.27 mA cm_Pt^-2 at 0.80 V), mass activity (0.51 mA µg_Pt^-1 at 0.80 V), and electrochemical active surface area (ECSA) (39.9 m² g^-1_Pt), surpassing commercial 20 % Pt/C by 2–3 times. Durability tests over 5000 potential cycles reveal excellent retention of mass activity (84 %) and specific activity (83.2 %) at 0.80 V, with only a minor 14 mV shift in half-wave potential. This enhancement stems from the synergistic effects between PtCo alloy nanoparticles and S, P-HCN, which modulate Pt- electronic structure, strengthen metal-support interactions, and boost catalytic efficiency. Single-cell HT-PEMFC studies demonstrate a peak power density of 377.4 mW cm⁻² for PtCo/S, P-HCN, comparable to commercial Pt/C (398 mW cm⁻²), with reduced voltage degradation at low current densities. This work presents a promising approach for improving cathode materials and advancing HT-PEMFC performance.