Oxygen vacancy-rich Z-scheme ZnIn2S4/Zn2TiO4 heterojunction nanofibers for pure water splitting with automatic product separation

Abstract

Photocatalytic pure water splitting is a viable strategy to resolve energy and environmental challenges. However, the practical application of pure water splitting is significantly restricted by inefficient charge carrier separation and the obstacle in the separation of conventional products of conventional products. In this study, the in-situ growth of ZnIn₂S₄ nanosheets on the surface of Zn₂TiO₄ nanofibers is successfully achieved through electrospinning and hydrothermal methods, thereby, resulting in ZnIn₂S₄/Zn₂TiO₄ composite nanofibers. Photocatalytic pure water splitting experiments reveal that the ZIS/ZTO-2 nanofibers exhibit H₂ and H₂O₂ evolution rates of 774.3 μmol∙g⁻¹∙h⁻¹ and 89.02 μmol∙g⁻¹∙h⁻¹, respectively, which are 5.2 times and 5.4 times higher than those of pure ZnIn₂S₄ nanosheets. The significant enhancement in photocatalytic activity is primarily attributed to the formation of Z-scheme heterojunction and the introduction of oxygen vacancies, which effectively promote the separation and transfer of photogenerated charge carriers. Additionally, the presence of oxygen vacancies selectively steers water oxidation toward H₂O₂ instead of O₂ via photogenerated holes, enabling the in-situ and automatic separation of H₂ and H₂O₂ during photocatalytic pure water splitting. Notably, ZIS/ZTO-2 achieves an apparent quantum efficiency of 19.66 % at a wavelength of 390 nm. This work provides a research foundation for constructing efficient photocatalysts for automatic product separation in photocatalytic pure water splitting.