ZnO/ZnS heterostructures grown on Zn foil substrate by hydrothermal method for photoelectrochemical water splitting

Abstract

ZnO nanorod arrays (NRAs) grown on the Zn foil substrate in the dual alkaline solution by hydrothermal method were first successfully utilized for photoelectrochemical (PEC) water splitting. ZnO NRAs were sufficiently covered on the Zn foil substrate via the reasonable match of the pH value, reaction temperature and reaction time through intensive experimental works. To enhance PEC performance, ZnS was coated on the surfaces of ZnO NRAs by ion exchange. The morphological, structural, optical and PEC characteristics of as-grown ZnO NRAs and ZnO/ZnS heterostructures were investigated. Compared with the pristine smooth and hexagonal ZnO NRAs, the surfaces of ZnO/ZnS heterostructures become rough and rounded in shape. Through the sulfidation treatment, some ZnO/ZnS heterostructures with a diameter of no more than 60 nm break and fade away, leading to a decrease in number density of ZnO/ZnS heterostructures. The texture coefficients of (002) diffraction peaks of ZnO decrease from 2.32 to 2.158. ZnO/ZnS heterostructures exhibit efficient separation rate of electron-hole pairs and enhanced visible light absorption, and thus have higher photocurrent density and photoconversion efficiency. In the polysulfide electrolyte solution, ZnO/ZnS heterostructures show good stability.