Titanium Dioxide/Reduced Graphene Oxide Hybrid Photocatalysts for Efficient and Selective Partial Oxidation of Cyclohexane

Partial oxidation of cyclohexane (CHA) to cyclohexanone (CHA-one) with molecular oxygen (O 2 ) is one of the most important reactions. Photocatalytic oxidation has been studied extensively with TiO 2 -based catalysts. Their CHA-one selectivities are, however, insufficient because the formed CHA-one is subsequently decomposed by photocatalysis involving the reaction with superoxide anion (O 2 ●– ) produced by one-electron reduction of O 2 on TiO 2 . Here we report that TiO 2, when hybridized with reduced graphene oxide (rGO), catalyzes photooxidation of CHA to CHA-one with enhanced activity and selectivity under UV light (λ > 300 nm). The TiO 2 /rGO hybrids produce CHA-one with twice the amount formed on bare TiO 2 with much higher selectivity (>80%) than that on bare TiO 2 (ca. 60%). The conduction band electrons photoformed on TiO 2 are transferred to rGO, promoting efficient charge separation and enhanced photocatalytic cycles. The trapped electrons on rGO selectively promote two-electron reduction of O 2 and suppress one-electron reduction. This inhibits the formation of O 2 ●–, which promotes photocatalytic decomposition of the CHA-one formed. These properties of rGO therefore facilitate efficient and selective formation of CHA-one on the hybrid catalyst.