Novel TiO2/Sb2S3 heterojunction with whole visible-light response for photoelectrochemical water splitting reactions

Abstract

Artificial photosynthesis represents a direct approach toward addressing energy and environmental issues by producing fuels such as hydrogen that can be used in fuel cells. Under the framework of Z-scheme water splitting, we develop a composite TiO₂ nanorod/Sb₂S₃ nanooctahedron photoanode, which possesses low onset potential and high photocurrent density. In this work, to mitigate the poor visible light absorption and low quantum efficiency of TiO₂, the concept of n/n heterojunction is introduced by using a composite composed of an additional n-type semiconductor and coating it on n-type TiO₂ nanorods. A stibnite Sb₂S₃ is selected as the coating material due to its suitable band-edge position and visible-light response. A photocurrent density of 0.79 mA cm⁻² (measured at 1.23 V vs. RHE) and onset potential of −0.08 V vs. RHE are obtained for the photoanode with the TiO₂ nanorod/Sb₂S₃ nanooctahedron structure in a 0.5 M Na₂SO₄ aqueous solution under AM 1.5G illumination. This successful combination of two n-type semiconductors provides a conceptual blueprint for material and conduction/valence band design as attractive catalysts for the photoelectrochemical water splitting reaction.