TiO₂ Nanopillar Arrays Coated with Oxygen-Doped ZnIn₂S₄ Nanosheets with the Elimination of S Vacancies for Photoelectrochemical Water Splitting

Abstract

Oxygen-doped ZnIn2S4 nanosheets with a suitable concentration of S-vacancies-coated TiO2 nanopillars (S-O-ZIS/TiO2) are successfully prepared on fluorine-doped tin oxide (FTO) substrates. The S-O-ZIS/TiO2 photoanode achieves a photocurrent density of 1.10 mA cm–2 at 1.23 VRHE under light illumination alongside a high incident photon-to-electron conversion efficiency (IPCE) value of 25.6% in a 1 M KOH electrolyte. The enhanced photoelectrochemical performance can be ascribed to several factors. First, the optimum oxygen doping modifies the energy band structure of ZnIn2S4, enhancing the light adsorption efficiency and facilitating the migration efficiency of the photogenerated carriers. In addition, the elimination of excess surface S vacancies avoids the negative effects of surface trap states, resulting in the efficient separation of photogenerated charges. Furthermore, the intimate connection between ZnIn2S4 and TiO2 accelerates the transport and separation of the photogenerated carriers. This work demonstrates the role of oxygen doping and S vacancies in photocatalysis and provides new insights into the design of high-efficiency photocatalysts.