Ru/FeOx catalyst performance design: Highly dispersed Ru species for selective carbon dioxide hydrogenation

A series of Ru/FeO x catalysts were synthesized for the selective hydrogenation of CO 2 to CO. Detailed characterizations of the catalysts through X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and temperature-programmed techniques were performed to directly monitor the surface chemical properties and the catalytic performance to elucidate the reaction mechanism. Highly dispersed Ru species were observed on the surface of FeO x regardless of the initial Ru loading. Varying the Ru loading resulted in changes to the Ru coverage over the FeO x surface, which had a significant impact on the interaction between Ru and adsorbed H, and concomitantly, the H 2 activation capacity via the ability for H 2 dissociation. FeO x having 0.01% of Ru loading exhibited 100% selectivity toward CO resulting from the very strong interaction between Ru and adsorbed H, which limits the desorption of the activated H species and hinders over-reduction of CO to CH 4 . Further increasing the Ru loading of the catalysts to above 0.01% resulted in the adsorbed H to be easily dissociated, as a result of a weaker interaction with Ru, which allowed excessive CO reduction to produce CH 4 . Understanding how to selectively design the catalyst by tuning the initial loading of the active phase has broader implications on the design of supported metal catalysts toward preparing liquid fuels from CO 2 .