Unraveling the role of Fe5C2 in CH4 formation during CO2 hydrogenation over hydrophobic iron catalysts

The production of value-added hydrocarbons by CO2 hydrogenation over iron (Fe) catalysts is an emerging platform reaction in CO2 utilization. However, CH4 forming in all hydrogenation reactions is undesirable. We focus on the role of Fe5C2 active species in CH4 formation during CO2 hydrogenation catalysis. Thus, Fe5C2 was manipulated by covering a hydrophobic shell to clarify the pathway of CH4 formation. By a combination of TPSR, in situ spectroscopies and DFT calculations, the variation in the mechanism of CH4 formation with the content of hydrophobic shell has been revealed. Meanwhile, the enhancement of H2O retention on the hydrophobic shell surface of Fe5C2 was found to inhibit the activation of CO2 by increasing energy barriers of C-C coupling reactions. Deep insights into the tunable role of Fe5C2 in the formation of CH4 can help for the further design of high performance catalysts for this reaction.