Photoelectrochemical performance enhancement of low-energy Ar+ irradiation modified TiO2

Low-energy Ar+ irradiation was used to prepare reduced TiO2 as photoanode having significantly improved PEC water oxidation performance. [Display omitted] •Low-energy Ar+ irradiation is a controllable method for vacancy engineering and surface morphology engineering of TiO2.•Ar-irradiated TiO2 exhibits significantly enhanced PEC water oxidation performance.•In-situ APXPS demonstrated that Ar+ irradiation can modify the interface and the interaction between the TiO2 surface and water.•Providing an effective method for evaluating critical factors in photocatalysis and for identifying the descriptor in dictating the PEC activity of metal oxides. To evaluate the effects of surface properties of semiconductor and enhance semiconductor’s activity for photocatalytic water oxidation, low-energy Ar+ irradiation was employed to modify the rutile TiO2 (110) surface and control the formation of oxygen vacancy density in TiO2, which was subsequently used for the photoelectrochemical (PEC) oxygen evolution reaction (OER). Specifically, by controlling the substrate temperature during Ar+ irradiation, the surface morphology and oxygen vacancy density of rutile TiO2 (110) could be modified, such that the effects of surface crystallinity, optical absorption and electrical properties of TiO2 could be compared for OER. We found that the intrinsic activity of TiO2 for PEC OER does not exhibit a scaling relationship with respect to the density of oxygen vacancy, optical adsorption or charge carrier concentration. Rather, a linear relationship could be observed between the photocurrent density and the interfacial charge-transport conductivity. Furthermore, ambient pressure X-ray photoelectron spectroscopy (APXPS) was used to investigate the effect of low-energy Ar+ irradiation on the interaction between TiO2 and water. It was demonstrated that using single crystal model systems with controlled properties, this study has thus provided a clear yet detailed analysis on key factors in tuning the photoelectrochemical performance of TiO2.