Controlled Synthesis of Nickel Phosphides: Mechanistic Insights and Catalytic Activity in Hydrogen Peroxide Production

Abstract

Strategically designing oxygen reduction reaction (ORR) electrocatalysts based on electronic structure is a pivotal method for enhancing the electrocatalytic activity and selectivity of two-electron (2e) reactions. While many transition metal phosphides, including NixPy, have demonstrated activity in electrocatalytic reactions, their effectiveness in 2e ORR electrocatalysis is still uncertain. In this study, guided by the theoretical insights into high electroactivity unveiled by the d-band center (Ed) theory, we engineered and synthesized Ni2P/Ni5P4 nanosheets (NSs). Functioning as 2e ORR electrocatalysts in alkaline environments, the Ni2P/Ni5P4 NSs exhibited outstanding 2e selectivity of up to 95%, with an electron transfer number close to two. Demonstrating a Faradaic efficiency exceeding 95% over a wide potential range (0.2 – 0.5 V), these NSs displayed extended stability for over 48 hours, outperforming most transition metal-based catalysts reported in literature. By employing density functional theory (DFT) calculations, the increased activity is ascribed to the adjustment of the d-band center at the engineered heterostructure interface, effectively regulating the adsorption energy of oxygen-containing intermediates (*OOH). This study offers crucial insights into the methodical design and production of effective transition metal phosphide electrocatalysts guided by the d-band center theory.