▎ 摘　　要

Graphene (GR) and its derivatives are generally assumed to be electron shuttles in order to explain the improved photocatalytic activity of their nanocomposites (such as TiO2/GR). However, it fails to account for the experimental results, which demonstrate that the photocatalytic activity of TiO2/reduced graphene oxide (RGO) is higher than that of TiO2/GR. Herein, we explore the underlying mechanism for the enhanced photocatalytic activity of TiO2/RGO (GR) by comparing several influential factors: band gap, band alignment near the gap, optical absorption, and active sites, via first-principles calculations. The results show that the small band gap, the type-II staggered band alignment, and the negatively charged O atoms as active sites in photocatalytic reactions are likely to be key factors for the photocatalytic activity of TiO2/RGO being better than that of TiO2/GR, partly offering a physical interpretation for related experimental results. Interestingly, the enhanced photocatalytic activity of TiO2/graphane (GRH) is also predicted. These results suggest that functionalized GR is most likely better than pristine graphene at improving the photocatalytic activity of TiO2/GR-based semiconductor photocatalysts.