Oxygen-vacancy-assisted construction of Ce–TiO₂ aerogel for efficiently boosting photocatalytic CO₂ reduction without any sacrifice agent

The development of efficient photocatalysts with high activity and high selectivity remains the biggest challenge limiting the development of photocatalysis. Herein, a novel Ce-doped TiO₂ aerogel (Ce–TiO₂) is synthesized via a simple one-step sol-gel technique, which integrates simultaneously supercritical drying, heat treatment, nano structuring, and self-diffusion for the formation of the Ce embedded in porous TiO₂ matrix with strong coupling. The Ce–TiO₂ aerogel exhibits typically homogeneous structures, and the resulting Ce–TiO₂ aerogel shows an extremely large BET specific surface area of 246.53 m²/g, which is responsible for the much-enhanced photocatalytic active sites. The incorporation of Ce has induced an impurity level in the band gap of the pristine TiO₂ aerogel, extending the light response range to the visible region. Meanwhile, the structural and compositional advantages are exploited to achieve fast separation and transfer of charge carriers. The yields of CH₄ and CO are 0.6 and 2.1 μmol/(g·h) under visible light without any additional co-catalysts or sacrificial agents, which are 1.4 and 15.6 times as high as those of pristine TiO₂ aerogel. In addition, the yields of CH₄ and CO are as high as 10.3 and 26.9 μmol/(g·h) under simulated solar spectrum conditions, which are 34.3 and 1.6 times as high as those of pristine TiO₂ aerogel. The density function theory (DFT) calculation confirms that the resulting Ce–TiO₂ aerogel enables efficient H₂O and CO₂ adsorption and activation through the Ce cooperation and O vacancy, which greatly improves photocatalytic CO₂ reduction. This work reveals the development of aerogel photocatalyst for the photoreduction of CO₂ with H₂O and CO₂ as feedstock.