Tailoring Electronic Structures via Ce/C Co-Doping and Oxygen Vacancy in TiO2 Aerogels for Enhanced Solar Fuel Production

A targeted modification approach involving the synthesis of Ce/C co-doped TiO2aerogels (CeCTi) via a sol–gel method combined with supercritical CO2drying and subsequent heat treatment is employed to enhance the photocatalytic CO2reduction performance of cost-effective and stable TiO2aerogels. The results demonstrate that the CeCTi exhibits a pearl-like porous network structure, an optical band gap of 2.90 eV, and a maximum specific surface area of 188.81 m2/g. The black aerogel sample shows an enhanced light absorption capability resulting from the Ce/C co-doping, which is attributed to the formation of oxygen vacancies. Under simulated sunlight irradiation, the production rates of CH4and CO reach 27.06 and 97.11 μmol g−1h−1without any co-catalysts or sacrificial agents, respectively, which are 82.0 and 5.7 times higher than those of the pristine TiO2aerogel. DFT reveals that C-doping facilitates the formation of oxygen vacancies, which introduces defect states within the calculational band gap of TiO2. The proposed photocatalytic mechanism involves the light-induced excitation of electrons from the valence band to the conduction band, their trapping by oxygen vacancies to prolong the charge carrier lifetime, and their subsequent transfer to adsorbed CO2molecules, thereby enabling efficient CO2reduction, which is experimentally supported by photoluminescence measurements.