Construction of Indium Oxide/N-Doped Titanium Dioxide Hybrid Photocatalysts for Efficient and Selective Oxidation of Cyclohexane to Cyclohexanone

Photocatalytic oxidation of cyclohexane (CHA) to generate cyclohexanone (CHA-one) is one of the most important strategic links for the production of nylon-6 and nylon-66. Herein, an indium oxide/N-doped titanium dioxide (In2O3/N-TiO2) hybrid photocatalyst with a p–n heterointerface was successfully constructed by a two-step strategy of the hydrothermal N-doped method and impregnation method with structural reconstruction. Under green and mild reaction conditions (room temperature, atmospheric pressure, and solvent-free), the In2O3/N-TiO2 hybrid catalyst achieved the desired photocatalytic performance for the production of CHA-one at simulated solar light. Compared with bare TiO2, the 5% In2O3/N-TiO2 composite achieved a 4-fold increase for producing CHA-one in catalytic activity and an increase in selectivity to the CHA-one of approximately 90%. Moreover, the In2O3/N-TiO2 composites exhibited a desirable cycling durability and recoverability. According to the photoelectrochemical tests and density functional theory (DFT) calculations, the enhanced photocatalytic performance of In2O3/N-TiO2 can be attributed to high visible-light absorption derived from N-doping and fast separation of photoformed electron–hole pairs caused by the p–n heterointerface. A possible photo-oxidation mechanism of CHA over the In2O3/N-TiO2 catalyst was proposed and verified by the trapping detection of active species. Thereby, the present approach provides a green and prospective strategy for extending the application of the TiO2-based photocatalyst for selective photo-oxidation.