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.