Hybrid TiO2/graphene derivatives nanocomposites: is functionalized graphene better than pristine graphene for enhanced photocatalytic activity?

Abstract

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.