Construction of Ni2P/CoP interface for highly efficient electrolysis of urea-assisted hydrogen production at industrial current densities

Abstract

Interface chemical modulation strategies are considered as promising method to prepare electrocatalysts for the urea oxidation reaction (UOR). However, conventional interface catalysts are generally limited by the inherent activity and incompatibility of the individual components themselves, and the irregular charge distribution and slow charge transfer ability between interfaces severely limit the activity of UOR. Therefore, we optimized and designed a Ni₂P/CoP interface with modulated surface charge distribution and directed charge transfer to promote UOR activity. Density functional theorycalculations first predict a regular charge transfer from CoP to Ni₂P, which creates a built-in electric field between Ni₂P and CoP interface. Optimization of the adsorption/desorption process of UOR/HER reaction intermediates leads to the improvement of catalytic activity. Electrochemical impedance spectroscopy and ex situ X-ray photoelectron spectroscopy characterization confirm the unique mechanism of facilitated reaction at the Ni₂P/CoP interface. Electrochemical tests further validated the prediction with excellent UOR/HER activities of 1.28 V and 19.7 mV vs. RHE, at 10 mA cm⁻², respectively. Furthermore, Ni₂P/CoP achieves industrial-grade current densities (500 mA cm⁻²) at 1.75 V and 1.87 V in the overall urea electrolyzer (UOR||HER) and overall human urine electrolyzer (HUOR||HER), respectively, and demonstrates considerable durability.