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

Oxygen-doped ZnIn 2 S 4 nanosheets with a suitable concentration of S-vacancies-coated TiO 2 nanopillars (S-O-ZIS/TiO 2 ) are successfully prepared on fluorine-doped tin oxide (FTO) substrates. The S-O-ZIS/TiO 2 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 ZnIn 2 S 4, 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 ZnIn 2 S 4 and TiO 2 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.