REACTION ENERGETICS FOR METHANOL SYNTHESI S 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. Act ivation energies for elementary reactions involved in the methanol syn thesis from CO2/H-2 over Cu(100) and Cu(100)-p(2x2) O surfaces have be en calculated using bond order conservation-Morse potential approach. The following conclusions have been obtained: the main pathway for met hanol 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 activa tion energy over the oxygen-modified Cu(100) surface; HCOOs is the com mon precursor intermediate for methanol and CO formations and the sele ctivity of methanol is governed by the relative reaction rate of hydro genolysis of formate to the dissociation of formate (to COs + OHs); Ov er the clean Cu(100) surface, the activation energy for formate hydrog enolysis is similar to that for formate dissociation to CO, and OH,, w hile 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.