Highly Selective Olefin Production from CO2 Hydrogenation on Iron Catalysts: A Subtle Synergy between Manganese and Sodium Additives

Mn and Na additives have been widely studied to improve the efficiency of CO2 hydrogenation to valuable olefins on Fe catalysts, but their effects on the catalytic properties and mechanism are still under vigorous debate. This study shows that Fe‐based catalysts with moderate Mn and Na contents are highly selective for CO2 hydrogenation to olefins, together with low selectivities for both CO and CH4 and much improved space‐time olefin yields compared to state‐of‐the‐art catalysts. Combined kinetic assessment and quasi in situ characterizations further unveil that the sole presence of Mn suppresses the activity of Fe catalysts because of the close contact between Fe and Mn, whereas the introduction of Na mediates the Fe–Mn interaction and provides strong basic sites. This subtle synergy between Na and Mn sheds light on the importance of the interplay of multiple additives that could bring an enabling strategy to improve catalytic activity and selectivity. A trace amount of Na additive not only promotes the CO2 hydrogenation rate and the olefin selectivity on Fe‐based catalysts, but also turns a Mn additive into a promoter by weakening the strong interaction between Fe and Mn species, leading to unprecedentedly high space‐time yields of olefins for CO2 hydrogenation.