Density Functional Theory Study on Surface CxHy Formation from CO Activation on Fe3C(100)

Spin-polarized density functional theory calculations have been performed to investigate the mechanismg for CxHy, formation on Fe3C(100). It is found that H-assisted CO dissociation (CO + H -> CHO; CHO -> CH + 0) has lower barrier than CO direct dissociation (CO -> C + O), but surface Cs atom hydrogenation to form surface CsH is the most favored pathway. As the first C-2 surface species, surface ketenylidene CsCO rising from CO adsorption is an important intermediate for C2Hx formation. Initial surface C2H, forms from CsCO hydrogenation instead of direct dissociation. The formation of CsCH, CsH2CH and CsH2CH has close effective barriers and depends on the CO/H-2 ratio. In addition, surface vacancy can activate CO strongly and lower the CO dissociation barrier considerably, and this regenerates the carburized active surface and closes a catalytic cycle.