Elementary steps in Fischer-Tropsch synthesis: CO bond scission, CO oxidation and surface carbiding on Co(0001)

Dissociation of CO on a Co(0001) surface is explored in the context of Fischer-Tropsch synthesis on cobalt catalysts. Experiments show that CO dissociation can occur on defect sites around 330 K, with an estimated barrier between 90 and 104 kJ mol^{- 1}. Despite the ease of CO dissociation on defect sites, extensive carbon deposition onto the cobalt surface up to 0.33 ML requires a combination of high surface temperature and a relatively high CO pressure. Experimental data on the CO oxidation reaction indicate a high reaction barrier for the CO + O reaction, and it is argued that, due to the rather strong Co-O bond, (i) oxygen removal is the rate-limiting step during surface carbidization and (ii) in the context of Fischer-Tropsch synthesis, removal of surface oxygen rather than CO bond scission might be limiting the overall reaction rate.