Synthesis of monolayer carbon-coated TiO2 as visible-light-responsive photocatalysts

Increasing visible light absorption and constructing an active surface for TiO2 have long been pursued to obtain high photocatalytic activities. Modifying TiO2 at an atomic scale is desirable to optimize its surface state and band structure but remains a huge challenge. Herein, we developed an ultrasmall (similar to 5 nm) visible-light-responsive TiO2 photocatalyst with a novel hybrid structure (TiO2/C) through a chemical vapor deposition process on large scale. Environmental in-situ transmission electron microscope studies confirmed the anatase TiO2 with a monolayer carbon shell in a hybrid structure. The resulted structure possesses narrowed bandgap 2.83 eV, favoring the enhanced visible-light-responsive photocatalytic activity. Density functional theory (DFT) simulations confirm the tunable mechanism of carbon-induced localized energy band within the bandgap of TiO2. As a physical barrier without turning TiO2 black, the monolayer carbon shell stabilizes Ti3+ inside TiO2, facilitates the separation of photo-induced carriers and enriches abundant absorbing sites of target pollutants. Consequently, the TiO2/C exhibits outstanding photocatalytic performance in both photoelectrochemical water oxidation and dye degradation under visible light besides superior activity for hydrogen evolution under simulated sunlight irradiation. This design proved a meaningful strategy in obtaining visible-light-responsive photocatalysts with a stable active surface for industrial application.