Phosphorus-Vacancy Density Regulation in Cobalt Phosphide for Efficient Bifunctional Urea-Assisted Energy-Saving Hydrogen Production

Abstract

Integrating the hydrogen evolution reaction (HER) with the urea oxidation reaction (UOR) offers an effective approach toward energy-efficient hydrogen production. Nevertheless, designing cost-effective and high-performance bifunctional electrocatalysts that can efficiently catalyze both HER and UOR remains a significant challenge. Herein, this work reports a cobalt phosphide (CoP) electrocatalyst with phosphorus vacancies. The introduction of phosphorus vacancies effectively redistributes the electronic structure of cobalt sites in CoP, accelerates interfacial charge transfer, and provides additional catalytically active sites, thereby significantly improving both HER and UOR performance. Electrochemical measurements reveal a clear correlation between vacancy density and catalytic activity, with higher phosphorus vacancy concentration leading to superior electrocatalytic behavior. For UOR, CoP-V P20 achieves a current density of 100 mA cm⁻² at a potential of 1.56 V. For HER, CoP-V P20 delivers a current density of 100 mA cm⁻² at a potential of -196 mV. This work provides valuable insights into defect-induced electronic modulation and offers a feasible pathway for the rational design of cost-effective, high-performance electrocatalysts for energy-efficient hydrogen production.