Interface Engineering of Fe‐Loaded ZnO Nanostructures via Wet Impregnation and Hydrothermal Routes for Enhanced CO Selectivity in CO ₂ Photoreduction

This study reports the synthesis of iron-doped zinc oxide nanocomposites (ZnO-FeO_x) via two distinct methods, hydrothermal (HT) and wet impregnation (WI), for photocatalytic CO2 reduction under both visible light (VLI) and ultraviolet irradiation (UVI) light irradiation. The (HT) approach yielded a doped solid solution, whereas the (WI) method produced a heterosystem with well-defined interfaces. The ZnO-FeO_x heterosystem demonstrated exceptional performance, achieving 99.99% selectivity for CO production with yields of 0.15 µmol g^-1 min^-1 (UVI) and 0.03 µmol g^-1 min^-1 (VLI). In comparison, the hydrothermally synthesized catalyst produced CO at yields of 0.042 µmol g^-1 min^-1 (UVI) and 0.006 µmol g^-1min^-1 (VLI) with 94% selectivity. These results correspond to an approximately sevenfold enhancement for the WI-synthesized catalyst and a twofold improvement for the (HT) synthesized material relative to pristine ZnO. Combined surface analysis and DFT calculations showed that iron incorporation generates interfacial impurity states that facilitate a unique charge-transfer pathway, enhancing CO₂ photoreduction. DRIFTS confirmed formate and carbonyl species as key intermediates in the reaction mechanism.