Transition metal-promoted Fe-based catalysts for photothermal catalytic CO2 hydrogenation†

Transition metal doping for Fe-based catalysts has been demonstrated in promoting the activity and regulating the selectivity in both the reverse water gas shift reaction and Fischer–Tropsch synthesis. However, there are few studies that concern their catalytic performance tailored by transition metal promoters under photothermal conditions. In this study, a series of typical MFeO_x (M = Mn, Co, Cu, Zn) catalysts were synthesized with a facile co-precipitation method and their photothermal CO₂ hydrogenation properties were evaluated. The results showed that the doping of Co, Cu, and Zn enhanced the activity and regulated the selectivity of Fe-based catalysts, e.g., CoFe achieving a C₂₊ yield of 1.73 mmol h⁻¹ g⁻¹ while ZnFe almost doubling the CO₂ conversion under irradiation. Mechanistic studies suggest that Co and Cu facilitated the reduction of Fe species, resulting in favorable CO₂ and H₂ activation. Lastly, a light-induced direct CO₂ dissociation pathway was proposed with in situ EPR and DRIFTS characterization and analysis of the undoped Fe and ZnFe catalysts. This study provides a novel perspective on transition metal promoters for photothermal CO₂ hydrogenation over Fe-based catalysts.