Anion doping and interfacial effects in B-Ni5P4/Ni2P for promoting urea-assisted hydrogen production in alkaline media

Abstract

A bifunctional catalyst used for urea oxidation-assisted hydrogen production can efficiently catalyze the urea oxidation reaction (UOR) and hydrogen evolution reaction (HER) simultaneously, thus simplifying electrolytic cell installation and reducing the cost. Constructing the heterointerface of two components or species and doping heteroatom are effective strategies to improve the performance of electrocatalysts, which could regulate the local electronic structure of the catalysts at their interface region, adjust their orbital overlap, and achieve enhanced catalytic performance. In this study, a simple hydrothermal method was studied for the preparation of B-doped Ni₅P₄/Ni₂P heterostructures on nickel foam (B-Ni₅P₄/Ni₂P@NF). Under 1 M KOH at a current density of 10 mA cm⁻², an overpotential of 76 mV was obtained for the HER. When 0.3 M urea was added to 1 M KOH, the performance of the prepared catalyst was greatly improved. When the current density reached 10 mA cm⁻², the potential was only 1.35 V. In addition, urea-assisted overall water splitting voltage was only 1.41 V. Thus, the B-Ni₅P₄/Ni₂P catalyst possess excellent electrocatalytic activity. The main reason for the excellent properties of the electrocatalyst is the construction of heterostructure, which regulates the electronic structure of the catalyst at its interface and generates a new efficient active site. In addition, the doping of B atoms further promotes the charge transfer rate, thus strengthening the interaction between two phases and improving the catalytic performance. This study provides a simple, environmentally friendly, and rapid design method to prepare an active bi-functional electrocatalyst that has a positive effect on urea-assisted overall water splitting.