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.