Solar-driven CO2 conversion over Co2+ doped 0D/2D TiO2/g-C3N4 heterostructure: Insights into the role of Co2+ and cocatalyst

Low charge separation efficiency is the critical limitation for solar-driven CO2 conversion into chemicals fuels. Accelerating charge transfer in the interface of photocatalysts is an intriguing approach to suppress charge recombination. Herein, Co2+ doped 0D/2D TiO2 quantum dots confined in graphitic carbon nitride (CoTiCN) heterostructure was prepared by in-situ pyrolysis of MOFs and urea. Co2+ serves as the bridge of linking 0D TiO2 and 2D g-C3N4 in the interface, and consequently accelerates charge transfer in the interface from 2D g-C3N4 to 0D TiO2. As a result, CO evolution rate for photocatalytic CO2 reduction reached 290 μmol g−1 h−1, much higher than those of pure g-C3N4 and TiO2/g-C3N4. In addition, photocatalytic mechanism study indicates that [Co(bpy)3]Cl2 in the system functions as cocatalyst without any photocatalytic activity under visible light irradiation. Electron transfer occurs from heterogeneous photocatalyst to [Co(bpy)3]Cl2, which acts as the electron transporter as active sites to catalyze CO2 reduction into CO. This work provides an insight into the design of metal doped 0D/2D material towards visible light driven CO2 reduction from the viewpoint of promoting charge transfer in the interface and the understanding of the photocatalytic mechanism of cocatalyst in system.