Photocatalytic reduction of CO2 by employing ZnO/Ag1-xCux/CdS and related heterostructures

Highlights: • CO₂ reduction activity using ZnO/M/CdS (M = Au, Ag and Pt) heterostructures is Au > Ag > Pt. • Alloying of Ag with Au enhances the photocatalytic activity by the heterostructures. • Alloying Ag with Cu remarkably improves the CO₂ reduction activity and suppresses the hydrogen evolution. • ZnO/Ag_0.5Cu_0.5/CdS exhibits CO₂ reduction in the absence of a sacrificial agent. In view of the great importance of finding ways to reduce CO₂ by using solar energy, we have examined the advantage of employing heterostructures containing bimetallic alloys for the purpose. This choice is based on the knowledge that metals such as Pt reduce CO₂, although the activity may not be considerable. Our studies on the reduction of CO₂ by ZnO/M/CdS (M = Ag, Au, Ag_1-xAu_x, Ag_1-xCu_x) heterostructures in liquid phase have shown good results specially in the case of ZnO/Ag_1-xCu_x/CdS, reaching a CO production activity of 327.4 µmol h⁻¹ g⁻¹. The heterostructures also reduce CO₂ in the gas-phase although the production activity is not high. Some of the heterostructures exhibit reduction of CO₂ even in the absence of a sacrificial reagent.