Coupling photocatalytic CO2 reduction with benzyl alcohol oxidation to produce benzyl acetate over Cu2O/Cu

Abstract

Photocatalytic reduction of CO₂ to produce valuable chemicals can simultaneously reduce the greenhouse effect and relieve the energy shortage pressure. However, CO₂ reduction over semiconductor-based photocatalysts usually generates C1 products. In this manuscript, we reported the preparation of a Cu₂O/Cu nanocomposite for photocatalytic CO₂ reduction under visible light. Since Cu₂O has a narrow band gap, photocatalytic CO₂ reduction over the as-obtained Cu₂O/Cu was carried out in the presence of benzyl alcohol as the sacrificial agent to inhibit the possible oxidation of Cu⁺ by the photo-generated holes and to complete the photocatalytic cycle over Cu₂O. It was found that benzyl acetate, instead of C1 products, was generated as the main product over Cu₂O/Cu, which can be ascribed to a successful coupling of CO₂ reduction and benzyl alcohol oxidation promoted by metallic Cu. After reaction, metallic Cu in Cu₂O/Cu was oxidized to CuO, which led to the deactivation of the catalyst. However, the catalyst can be regenerated by reduction to recover its performance for producing benzyl acetate. The strategy by coupling photocatalytic CO₂ reduction with the oxidation of organics not only can lead to valuable multi-carbon organics from CO₂ reduction, but also can be used to inhibit the photo-corrosion of narrow-band gap semiconductor-based photocatalysts during photocatalytic reactions.