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

Abstract

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.