TiO₂ NanopillarArrays Coated with Oxygen-DopedZnIn₂S₄ Nanosheets with the Elimination of SVacancies 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 V_RHE 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.