Efficient in situ Formation of Fe5C2 from Alkali Metal-doped Ru/Fe2C)3 during CO2 Hydrogenation

Fe5C2 has been widely used as a catalyst in CO2 hydrogenation to produce useful compounds because of its high activity for C-C bond formation. Since the formation of Fe5C2 usually requires the prolonged pretreatment of iron oxide with H2 or syngas (CO + H2), catalysts that efficiently form Fe5C2 during CO2 hydrogenation are desirable. In this study, we developed alkali metal-doped Fe2O3-supported Ru catalysts that efficiently formed Fe5C2 during CO2 hydrogenation and suppressed the selectivity of hydrocarbons, especially methane, compared to Ru/Fe2O3. After the reaction, Fe5C2 formation from Ru/Fe2O3 was more efficient with K, Rb, and Cs than with Li and Na coexisting. Various characterizations for K-Ru/Fe2O3 demonstrated that the supported Ru nanoparticles were covered by in situ formed Fe5C2. The efficient formation of Fe5C2 during CO2 hydrogenation, the coverage of Ru nanoparticles by Fe5C2 and the formation of a Ru core-Fe5C2 shell structure could be attributed to the synergistic effects of iron oxide reduction promoted by Ru-mediated hydrogen spillover and the enhancement of dissociative CO adsorption by alkali metais.

Automated summary

In this study, alkali metal-doped Ru catalysts were developed that efficiently formed Fe5C2 during CO2 hydrogenation and suppressed the selectivity of hydrocarbons. The efficient formation of Fe5C2 was attributed to the synergistic effects of iron oxide reduction promoted by Ru-mediated hydrogen spillover and the enhancement of dissociative CO adsorption by alkali metals.