Fig. 6: Proposed light-assisted CO₂ hydrogenation mechanism.

a Electron transfer between Cu and ZnO under irradiation by different light spectral ranges. The equations below the schematics indicate the potential reactions which could be improved when interacting with certain light-generated electrons. The potential electron acceptors are highlighted. b The light-aided CO₂ hydrogenation reaction over Cu/ZnO/Al₂O₃ system. Pathways for CO (chemisorbed CO₂ dissociation or ZnO–HCOO* decomposition) and methanol production (Cu–ZnO interface mediated processes) are illustrated with black and orange arrows, respectively. A dynamic population of species on Cu surface (Cu(I), H*, CO₃*, CO*), ZnO surface (OH*, CO₃*/HCO₃*, HCOO*) and Cu–ZnO interface perimeter (HCOO*, H₂CO, H₃CO*) under reactive condition are envisioned. The electrons transferred to Cu surface promote CO₂ dissociation to CO (green dotted rectangle), while the light-mediated methanol production is attributed to the promoted H*-supply and HCOO*-hydrogenation (glowing dark arrow) at the Cu–ZnO interface perimeter (red dotted rectangle) under dual excitation of Cu and ZnO.