Synergistic effect of K and Zn on Fe-based catalysts for efficient CO 2 hydrogenation.

Excessive emission of CO ₂ into the atmosphere has severely impacted the global ecological environment. Converting CO ₂ into valuable chemicals and fuels is of great significance for sustainable development. However, low activity and undesirable selectivity often result from the inherent inertness of CO ₂ . Herein, K- or/and Zn-modified Fe-based catalysts were prepared by an incipient-wetness impregnation method for CO ₂ hydrogenation via a cascade reaction. The results indicate that K species exist as K ₂ O while Zn species exist as ZnFe ₂ O ₄ . In the CO ₂ hydrogenation pathway, K ₂ O facilitates the adsorption of CO ₂ and restrains the adsorption of H ₂ , accelerating the transformation of CO ₂ into C ₂ -C ₄ olefins rather than paraffins while Zn species promote the dispersion of Fe species, leading to improved activity. Synergistically, a K- and Zn-modified Fe-based catalyst (2Zn-10K-Fe/Al) shows excellent catalytic CO ₂ hydrogenation activity, achieving a CO ₂ conversion of 77% which is 1.8 times that (42%) of the unmodified Fe-based catalyst (Fe/Al). Our catalyst also shows a significantly promoted selectivity to C ₂ -C ₄ olefins of 17% in comparison with the Fe/Al catalyst (0%). It is envisioned that such a binary effect of elements might contribute to the low-cost and industrial production of Fe-based catalysts for selective CO ₂ conversion.