Efficient Photocatalytic Reduction of CO2 Using Carbon-Doped Amorphous Titanium Oxide

CO2-related solar to chemical conversions have gained extensive interest due to the great concerns on renewable energy utilization. Here, we have demonstrated a new synthetic route to C-doped amorphous titanium oxide using a facile citric acid assisted sol-gel method for efficient photocatalytic reduction of CO2. The synthesized amorphous material exhibits a mesoporous structure with high specific surface area and a significantly narrowed band gap of 2.1eV, which are crucial for solar light harvesting and adsorption/chemical activation of CO2 for energy transformation. The amorphization, mesoporous structure, and the band structure of the C-doped samples were also successfully tuned by controlling the annealing temperatures. The optimized catalyst annealed at 300 degrees C shows the highest specific surface area, favorable visible-light response as well as the considerable performance for CO2 photoreduction. Moreover, the further treatment of Al reduction can induce numerous surface oxygen vacancies on the amorphous sample and thus efficiently restrain the recombination of photogenerated carriers. Of significant importance is that the Al-reduced catalyst achieves excellent performance with the space-time yield of CH4 and CO of 4.1 and 2.5molg(-1)h(-1) for solar light, and 0.53 and 0.63molg(-1)h(-1) for visible light, respectively. This sample is also stable for photocatalytic CO2 transformation.