Defected ZnWO ₄-decorated WO ₃ nanorod arrays for efficient photoelectrochemical water splitting†

Abstract

The utilization of solar energy in photoelectrochemical water splitting is a popular approach to store solar energy and minimize the dependence on fossil fuels. Herein, defected ZnWO ₄-decorated WO ₃ nanorod arrays with type II heterojunction structures were synthesized via a two-step solvothermal method. By controlling the amount of Zn precursor, WO ₃ nanorods were decorated in situ with tunable amounts of ZnWO ₄ nanoparticles. Characterization confirmed the presence of abundant W ⁵⁺ species in the defected ZnWO ₄-decorated WO ₃ samples, leading to enhanced light absorption and charge-separation efficiency. Therefore, the decorated WO ₃ nanorod arrays show much higher photoelectrochemical (PEC) activity than pure WO ₃ nanorod arrays. Specifically, the sample with optimal ZnWO ₄ decoration and surface defects exhibits a current density of 1.87 mA cm ⁻² in water splitting at 1.23 V vs. RHE under 1 sun irradiation (almost 2.36 times higher than that of pure WO ₃), a high incident photon-to-current efficiency of nearly 40% at 350 nm, and a relatively high photostability. However, the decoration of WO ₃ with too much ZnWO ₄ blocks the light absorption of WO ₃, inhibiting the PEC performance, even when many defects are present. This work provides a promising approach to rationally construct defected heterojunctions as highly active PEC anodes for practical applications.

Abstract

A strategy based on a solvothermal method was developed to construct defected ZnWO ₄-decorated WO ₃ photoanodes for efficient photoelectrochemical water splitting.