Advanced photoelectrochemical performance of inverse-opal heterostructures fabricated using hydrogenated ZnO and TiO2

Abstract

Semiconductor-based photocatalysts have attracted considerable attention due to their great potential in environmental protection and solar energy conversion. Owing to their advantages of nontoxicity and low cost, ZnO and TiO₂ are promising candidates for use as semiconductor photocatalysts; however, their development and large-scale applications have always been limited by poor absorption in the visible light region and high charge carrier recombination rates. In this work, hydrogenated ZnO inverse opals (IOs), hydrogenated TiO₂ IOs, and their inverse-opal heterostructures with advanced visible light absorption properties were prepared. The hydrogenated ZnO IOs exhibit superior absorption capacity within the incident light range of 300–800 nm and a transient photocurrent density of around 1.4 mA cm⁻², which is 2.8 times that of pristine ZnO IOs. Meanwhile, the photocurrent density of hydrogenated TiO₂ increases by 6 times. Three different types of heterostructures were successfully fabricated to obtain the optimal photoelectrochemical performance using hydrogenated ZnO and hydrogenated TiO₂ IOs. In particular, the heterostructure, comprising hydrogenated TiO₂ inverse opals prepared by atomic layer deposition as the bottom-layer material and hydrogenated ZnO inverse opals prepared by electrochemical deposition as the top-layer material, exhibits a remarkable absorptivity reaching ∼94% across the entire visible light range except for the photonic band gap. It demonstrates an advanced photocurrent density of ∼1.77 mA cm⁻² under an incident illumination of 100 mW cm⁻².