Atomic layer deposition of sulfur-defective ZnS on TiO2: Tailoring optical and electronic properties for visible-light-driven water splitting

Abstract

Atomic layer deposition (ALD) was employed in this work to fabricate atomically thin ZnS layers on mesoporous TiO₂ films. Unlike conventional ZnS deposition methods, the ALD process resulted in sulfur-deficient ZnS films with a distinctive yellow hue. Spectroscopic analysis confirmed a reduced bandgap of 2.2 eV and a modified electronic structure, attributed to sulfur vacancies. The formation of a type II heterojunction between ZnS and TiO₂ was also verified through in-depth spectroscopic studies. This novel photoelectrode demonstrated exceptional photoelectrochemical performance, exhibiting a significantly high photocurrent and a remarkable charge separation efficiency of up to 94 % under visible light illumination in neutral water. These results highlight the potential of defect engineering in enhancing the photoelectrochemical activity of semiconductor materials for sustainable energy applications.