Photoelectrochemical Performance Enhancement of Low-energy Ar+ Irradiation Modified TiO2

Abstract 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.