Synergistic effect of Pt-Ni dual single-atoms and alloy nanoparticles as a high-efficiency electrocatalyst to minimize Pt utilization at cathode in polymer electrolyte membrane fuel cells.

Pt-Ni (111) alloy nanoparticles (NPs) and atomically dispersed Pt have been shown to be the most effective catalysts for oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs) as well as less expensive compared to pure Pt NPs. To meet reaction kinetic demands and minimize the Pt utilization at cathode in PEMFCs, we propose a novel electrocatalyst composed of dual single-atoms (Pt, Ni) and Pt-Ni alloy NPs dispersed on the surface of N-doped carbon (NDC); collectively, PtNi-NDC. The optimized PtNi-NDC catalyst displays excellent mass activity and durability compared to commercial Pt/C. Electrocatalytic measurements show that the PtNi-NDC catalyst, with a metal loading of 4.5 wt%, exhibited distinguished ORR performance (E = 0.912 V) through a 4-electron (4e) pathway, which is higher than that of commercial 20 wt% Pt/C (E = 0.857 V). The DFT simulations indicate Pt-Ni alloy NPs and PtNiNC atomic structure are the mobile active sites for ORR catalytic activity in PtNi-NDC. As a cathode catalyst in PEMFC, the Pt utilization efficiency in the PtNi-NDC catalyst is 0.033 g kW, which is 5.6 times higher than that of commercial Pt/C (0.185g kW). Therefore, the consumption of precious metals is effectively minimized.