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

Abstract

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 O₂ 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.