Defected ZnWO-decorated WO nanorod arrays for efficient photoelectrochemical water splitting.

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-decorated WO nanorod arrays with type II heterojunction structures were synthesized a two-step solvothermal method. By controlling the amount of Zn precursor, WO nanorods were decorated with tunable amounts of ZnWO nanoparticles. Characterization confirmed the presence of abundant W species in the defected ZnWO-decorated WO samples, leading to enhanced light absorption and charge-separation efficiency. Therefore, the decorated WO nanorod arrays show much higher photoelectrochemical (PEC) activity than pure WO nanorod arrays. Specifically, the sample with optimal ZnWO decoration and surface defects exhibits a current density of 1.87 mA cm in water splitting at 1.23 V RHE under 1 sun irradiation (almost 2.36 times higher than that of pure WO), a high incident photon-to-current efficiency of nearly 40% at 350 nm, and a relatively high photostability. However, the decoration of WO with too much ZnWO blocks the light absorption of WO, 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.