Dual single atoms (Pt, Ni) and PtNi alloy nanoparticles encapsulated N-doped carbon framework for durable ORR and HER electrocatalysts

Abstract

High-activity, stable, and high-efficiency bifunctional Pt-based catalysts that promote oxygen reduction reactions (ORRs) and hydrogen evolution reactions (HERs) are urgently needed to meet the ever-intensifying energy demands. In this paper, we propose a novel strategy for enhancing an electrocatalyst's durability using a high-porosity and abundantly nitrogen-doped carbon framework (NDCF) support derived from ZIF-8. PtNi alloy nanoparticles (NPs) surrounded by dense dual single atoms (SAs) of Pt and Ni were immobilized in a porous NDCF matrix (PtNi_SA-NPs/NDCF), synergistically exhibiting bifunctional catalytic activity and durability toward ORR and HER. Under acidic conditions, the PtNi_SA-NPs/NDCF exhibits a half-wave potential of 0.91 V and a favorable 4-electron pathway for ORR. It also displays an overpotential of 24.7 mV at a current density of 10 mA cm⁻² and a mass activity of 6.1 A mg_Pt⁻¹ (at 40 mV), indicating ultrahigh electrocatalytic activity for HER. Critically, the PtNi_SA-NPs/NDCF showed remarkable durability over 10,000 CV cycles, reducing ORR's half-wave potential by only 4 mV and HER's overpotential by a mere 6 mV at 10 mA cm⁻². We attribute this enhancement in durability to the stable graphitic carbon shell encapsulating the PtNi alloy NPs and the enrichment of pyridinic-N coordination by the NDCF support.