Ultrathin HNb3O8 nanosheets with oxygen vacancies for enhanced photocatalytic oxidation of amines under visible light irradiation

Abstract

Ultrathin HNb₃O₈ nanosheets (HNb₃O₈ NSs) with oxygen vacancies were successfully synthesized by a simple bottom-up hydrothermal process. The obtained nanosheets were uniform with a thickness of about 3.02 nm and the surface oxygen vacancies on the HNb₃O₈ nanosheets were confirmed by electron spin resonance spectroscopy (ESR) and X-ray photoelectron spectroscopy (XPS). As compared to urchin-like Nb₂O₅ nanospheres and Nb₂O₅ nanorods, ultrathin HNb₃O₈ nanosheets with oxygen vacancies showed higher activities in the photocatalytic oxidative coupling reaction of benzylamine under visible light irradiation. The improved photocatalytic activity of HNb₃O₈ NSs was attributed to the following: (1) unique nanosheet structure with different molecular thicknesses that led to the effective separation of the photogenerated carriers; (2) a benzylamine-HNb₃O₈ surface complex formed on the oxygen vacancies, which reduced the bandgap of HNb₃O₈ NSs and was beneficial to harvest visible light; (3) HNb₃O₈ NS-V could efficiently chemisorb O₂ molecules and promote the activation of O₂ to reactive oxygen species.