Density functional calculations to study the mechanism of the Fischer-Tropsch reaction on Fe(111) and W(111) surfaces

Density functional theory calculations for the Fischer-Tropsch synthesis on Fe(111) and W(111) surfaces elucidate the mechanisms of CO activation, hydrogenation of CH_x (x = 0-3) species, and C-C coupling. CO prefers to form intermediate CHO before C-O bond scission rather than through direct dissociation of its C-O bond on both Fe(111) and W(111) surfaces. CH is the most abundant species adsorbed on these two surfaces; the coupling reaction of CH + CH is the most likely process on the Fe(111) surface with a calculated barrier with a height of 0.54 eV. Two favorable coupling reactions, CO + CH and CH + CH, on the W(111) surface have calculated reaction barriers with heights of 0.26 and 0.35 eV, respectively. To understand the interaction between adsorbates and surfaces, we calculated the Bader charges and analyzed the densities of states.