Integration of TiO₂/ZnIn₂S₄ p‐n Heterojunction with Titanium Defects to Boost PEC Oxygen Production

Abstract

TiO2 is a widely used photoelectric conversion semiconductor material. However, due to its selective absorption of ultraviolet light and high recombination rate of photogenerated carriers, it exhibits poor photoelectrochemical water splitting performance. In this study, intrinsic defect titanium vacancy and semiconductor recombination agents ZnIn2S4 were introduced into an anodization‐annealed TiO2 film (TiO2 NT) to enhance the photoanode activity. The activity‐enhanced TiO2 photoanode (ZIS@TiO2 NT‐EA) was characterized by surface analyses and photoelectrochemical measurements. The results indicated that the introduction of titanium vacancies into the TiO2 NT‐EA changed its semiconductor type from n to p. After the ZnIn2S4 nanoparticles were loaded on the TiO2 NT‐EA film, the carrier concentration of the ZIS@TiO2 NT‐EA increased nearly 12 times than the pristine TiO2 NT. Due to the higher carrier separation efficiency resulting from the formation of p‐n heterojunction, the photocurrent density of the ZIS@TiO2 NT‐EA reached 3.89 mA cm‐2 at 1.23 V vs. RHE, nearly 3 times higher than that of the original TiO2 NT. The maximum applied bias photon‐to‐current efficiency (ABPE) value of the ZIS@TiO2 NT EA reached 2.15% at 0.496 V vs. RHE, which is very competitive if compared with all the reported TiO2 film electrodes in the PEC water splitting application.