Reaction energetics for methanol synthesis from CO2/H-2 over the clean and the oxygen-modified Cu(100) surfaces

Clean and oxygen-modified Cu(100) surfaces have been used to model the metallic and the partially oxidized copper surfaces respectively. Activation energies for elementary reactions involved in the methanol synthesis from CO2/H-2 over Cu(100) and Cu(100)-p(2x2) O surfaces have been calculated using bond order conservation-Morse potential approach. The following conclusions have been obtained: the main pathway for methanol formation can be expressed as ''CO2,s-->HCOOs-->H2COs-->CH3Os-->CH3OHs''; In comparison with that over the clean Cu(100) surface, each elementary reaction involved in methanol synthesis has a lower activation energy over the oxygen-modified Cu(100) surface; HCOOs is the common precursor intermediate for methanol and CO formations and the selectivity of methanol is governed by the relative reaction rate of hydrogenolysis of formate to the dissociation of formate (to COs + OHs); Over the clean Cu(100) surface, the activation energy for formate hydrogenolysis is similar to that for formate dissociation to CO, and OH,, while the former is much lower than the latter over the oxygen-modified Cu(100) surface, Judging by the activation energies, we conclude that methanol synthesis from CO2/H-2 is more favorable over the partially oxidized copper surface than that over the metallic copper surface.