Adjusting the CO2 hydrogenation pathway via the synergic effects of iron carbides and iron oxides

Abstract

Owing to the chemical inertness and thermodynamic stability of CO₂, efficiently regulating product selectivity during CO₂ hydrogenation is still a big challenge. Without impairing the CO₂ reactivity and stability, outstanding selectivity values, where 73.2% of the total hydrocarbon products were alkenes (CO free) and 97.9% of the total alcohol products were C₂₊ alcohols (87.4% ethanol), were achieved using a Na-promoted Fe₃O₄ microsphere catalyst. Significantly, compared to the literature results relating to CO₂ hydrogenation, the highest yields of alkenes (22.03%) and ethanol (11.23%) were achieved in this work. Multiple characterization results demonstrate that the Na promoter contributes to tuning the composition of the iron oxides and iron carbides. In situ CO₂-DRIFTS and NAP-XPS results revealed that the key step in ethanol formation is considered to be the bonding of adsorbed CHO* and *CH_x. Synergistically utilizing the distinct catalytic roles of iron carbides and iron oxides can guide the design of effective catalysts and provide fundamental understanding relating to CO₂ hydrogenation.