Facile preparation of nickel phosphide for enhancing the photoelectrochemical water splitting performance of BiVO4 photoanodes

Abstract

The photoelectrochemical (PEC) water splitting performance of BiVO₄ (BVO), a promising photoanode material, is constrained by its extremely short hole diffusion length and slow water oxidation kinetics. Modification of oxygen evolution cocatalysts (OECs) by appropriate methods is a practical solution to enhance the PEC water splitting performance of BVO. In this work, two different nickel phosphides Ni₂P and Ni₁₂P₅ were prepared by a facile and mild one-step solvothermal method, and used as OECs to modify a BVO photoanode for enhancing the PEC water splitting performance. The BVO/Ni₂P and BVO/Ni₁₂P₅ photoanodes showed impressive photocurrent densities of 3.3 mA cm⁻² and 3.1 mA cm⁻², respectively. In addition, the PEC water splitting stability of the BVO/Ni₂P photoanode was greatly enhanced compared to that of the bare BVO photoanode. Further characterization and photoelectrochemical analysis revealed that the significant improvement of the BVO photoanode performance was attributed to the effective inhibition of surface charge recombination, facilitation of interfacial charge transfer, and acceleration of water oxidation kinetics after Ni₂P and Ni₁₂P₅ modification.