Ag–CeO₂ Composite Aerogels as Photocatalysts for CO₂ Reduction

Composite aerogels with a metallic Ag phase and a semiconductor CeO2 phase are prepared using a conventional epoxide assistant sol–gel method and ethanol supercritical drying. In such an aerogel, CeO2 nanoparticles surround Ag nanoparticles to form a continuous network for mass and charge transfer. The photocatalytic CO2 reduction reaction is studied on the gas–solid interface of the composite aerogels. It is found that with the Ag additives, the activity of the composite aerogels is greatly improved compared with that of pristine CeO2, both under the full-spectrum light and visible light. A high CH4 yield up to 21.9 μmol/g/h and high selectivity can be simultaneously achieved in a composite aerogel containing ∼5 wt.% Ag. Such an enhancement is attributed to the surface plasmon resonance effect brought by Ag, which promotes charge generation and separation efficiency in the composite aerogel.