Construction of glucose precursor carbon/TiO₂ heterojunction with high ligand-to-metal charge transfer (LMCT) for visible light driven CO₂ reduction

Well-designed fabrication of glucose precursor carbon-doped TiO2 heterojunction with high Ligand-to-Metal Charge Transfer (LMCT) for enhancing photocatalytic CO2 conversion has been examined. Photocatalysts were fabricated using a single-step thermal method and tested in a fixed-bed reactor under visible light. The 6 % glucose precursor carbon-doped over TiO2 (6 %C/TiO2) photocatalyst has demonstrated excellent activity in converting CO2 to CO and CH4 under visible light. The main product yield, CO of 739.9 mu mol g-cat(-1) was produced over 6 %C/TiO2, which is 4.4 folds the amount of CO obtained over TiO2 (168.7 mu mol g-cat(-1)). The XPS findings reveal the presence of different surface components containing C-OH, C=C, and C=O functional groups, which contribute to the formation of a ligand-metal-charge-transfer (LMCT) complex between carbon and TiO2 photocatalyst. Carbon-doped TiO2 possesses a narrow energy band and the ability to effectively absorb solar light, which enables efficient transportation of electrons generated by photon excitation. The mechanism of the carbon-doped TiO2 in CO2 conversion to CO and CH4 is postulated to be consistent with the LMCT complex phenomena. Therefore, carbon-doped TiO2 provides heterojunction for localization of electrons, impedes the rate at which charges recombine, and reduces the band gap energy, leading to improved photocatalytic performance when exposed to visible light.