Activity and selectivity descriptors for iron carbides in CO2 hydrogenation

CO2 conversion into value-added products provides an attractive way to close carbon cycles and to minimize the dependence on oil-based feedstock. To understand how product distribution in CO2 hydrogenation can be controlled, as required for purposeful catalyst design, we prepared single-phase alpha-Fe2O3 materials differing in their reducibility due to the different size of crystallites and the presence of planar defects in the iron sublattice. Their structural evolution during reduction and under CO2 hydrogenation conditions as well as their catalytic and adsorptive properties towards CO, CO2, and H2 were elucidated through combining kinetic (spatially resolved), physicochemical and chemisorption analyses. The obtained results suggest that the reducibility of alpha-Fe2O3 is a key factor affecting in situ transformation of this oxide into Fe5C2 with planar defects, which seem to determine the generation of surface intermediates from CO, CO2, and H2, and accordingly CO2 hydrogenation to CO exclusively or also CO hydrogenation to hydrocarbons.