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

Abstract

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 2.1 eV, 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 °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 2.5 μmol g⁻¹ h⁻¹ for solar light, and 0.53 and 0.63 μmol g⁻¹ h⁻¹ for visible light, respectively. This sample is also stable for photocatalytic CO₂ transformation.