Construction of Co-doped TiO2/rGO nanocomposites for high-performance photoreduction of CO2 with H2O: Comparison of theoretical binding energies and exploration of surface chemistry

Abstract

We report the enhancement of the photocatalytic performance of CO2 reduction in H2O by introducing Co and reduced graphene (rGO) into TiO2 photocatalyst. The synthesized nanocomposites were characterized by a range of analyses including X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), ultraviolet–visible light diffuse reflectance spectra (UV–vis DRS), Fourier transform infra-red spectroscopy (FT-IR), thermogravimetry-differential scanning calorimetry (TGA-DSC), energy dispersive X-ray analysis (EDX), Brunauer-Emmett-Teller (BET) surface area and X-ray photoelectron spectroscopy (XPS). It was found that wrapping Co-doped TiO2 with rGO expanded the light absorption ability of Co-doped TiO2/rGO, thus, improving the photoreduction efficiency of CO2 and selectivity for methanol. The conversion yields of CO2 to methanol with TiO2, Co-doped TiO2 and Co-doped TiO2/rGO reached 32.3 μmol/gcat, 730 μmol/gcat and 936 μmol/gcat, respectively, after 7 h of irradiation. Theoretical studies via Density functional theory (DFT) revealed that doping TiO2 with Co ions facilitated the formation of adsorbed carbonate or CO2•- species, as CO2 adsorbs onto Co-doped TiO2 surface with binding energy (BE) of −18.12 kJ/mol. The research will deepen the understanding of mole ratio (Ti:Co) content on the nanocomposites performance and provide new ideas for designing efficient photocatalysts.