Carbon coating stabilized Ti3+-doped TiO2 for photocatalytic hydrogen generation under visible light irradiation

Self-doping by Ti3+ is a useful method to expand the light response of TiO2 into the visible light region. However, to obtain a stable Ti3+-doped TiO2 seems to be a challenge due to the easy oxidation of Ti3+ during the heterogeneous reaction. Here, we propose a simple carbon coating route to stabilize the Ti3+-doped TiO2, in which both the Ti3+ and precursor of the carbon coating layer were in situ formed from the hydrothermal hydrolysis of titanium isopropoxide. The carbon coated Ti3+-doped TiO2 exhibited excellent stability for photocatalytic hydrogen production. Based on electron paramagnetic resonance (EPR) analysis, the proposed stabilizing mechanism is that the conductive carbon coating layer as a barrier layer prevents the H2O and O-2 from diffusing into the surface of the photocatalyst, which can oxidize the surface O vacancies and Ti3+ in TiO2. Our findings offer a simple route to prepare a highly stable TiO2-based photocatalyst with visible light response.