Selective synthesis of olefins via CO2 hydrogenation over transition-metal-doped iron-based catalysts

The catalytic hydrogenation of CO2 to olefins has received considerable attention. Herein, transition metal- and sodium-modulated iron-based catalysts were fabricated. Doping with zinc and copper favor the formation of Fe3O4 and Fe5C2 active phases, while adding manganese inhibits the formation of iron carbide. In addition, phase separation between copper and iron species occurs more readily under working conditions. Therefore, a zinc- and sodium-modulated Fe catalyst exhibited the best activity and stability. Moreover, copper was predicted to substantially decrease the energy barrier of the rate-determining step for the secondary hydrogenation of olefins and result in a much lower olefin-to-paraffin ratio. In addition, the ZnO/Fe5C2 interface facilitated the desorption of olefins from the catalyst surface and inhibited the undesirable secondary reaction of olefins, enabling a high selectivity toward olefins of 36.9 % C2–4= and 32.3 % C5+=. This study provides an exemplary new strategy for tuning the product selectivity of catalysts for olefin synthesis.