CeO₂ Nanostructures Enriched with Oxygen Vacancies for Photocatalytic CO₂ Reduction

Synthesizing nanomaterials at the expense of solar energy and the associated energy generation have utmost significance as far as environmental sustainability is concerned. Here, sunlight-assisted combustion synthesis of a nanoscale metal oxide (CeO₂) is reported. The sunlight, as a clean renewable energy source, is used for the first time to initiate the exothermic combustion reaction and to introduce oxygen vacancies into the CeO₂. The current synthesis setup controls the environmental problems of gas evolution, usually associated with the conventional method, and thus maintains the green pathway. Additionally, for comparison, CeO₂ nanoparticles are also synthesized using the conventional solution combustion method (CeO₂-CSC). It is found that the CeO₂ synthesized using sunlight-assisted combustion (CeO₂-SAC) possesses a smaller particle size, a higher concentration of oxygen vacancies, and a narrower band gap than the CeO₂-CSC. Therefore, CeO₂-SAC demonstrates higher photocatalytic performance in converting CO₂ to CH₃OH (0.702 μmol h^-1 g^-1) than the CeO₂-CSC (0.397 μmol h^-1 g^-1), thus pointing toward environmentally benign photocatalytic CO₂ reduction.