The acceleration of methanol synthesis and C2 oxygenates formation on copper grain boundary from syngas

Density functional theory is employed to investigate the Fischer-Tropsch mechanism on copper Sigma 5(310) tilt grain boundary together with Cu(111) surface. For the methanol formation, Cu Sigma 5(310) can effectively reduce each energy barrier through the preferred CH3O intermediate route as compared with Cu(111). Furthermore, Cu Sigma 5(310) provides a synergetic effect to modulate the energy landscape in the methanol synthesis, where the pathway associated with CH2OH (CH2O <-> CH2OH <-> CH3OH) presents the clear kinetic advantage than the CH3O route. Simultaneously, the kinetically assisted intermediate CH2OH enable the CH2 production both thermodynamically and kinetically on Cu Sigma 5(310). The formation of C2 oxygenates from CH2 provides a critical precursor to higher alcohol synthesis. The higher activity of grain boundary is attributed to the presence of low-coordinated sites with flexible local configuration. Consequently, the adsorption strength of small species is enhanced to provide a thermodynamic driving force for C-O bond scission. The adaptive character of Sigma 5(310) grain boundary facilitates the stabilization of the transition state, therefore lowering the activation barrier. Present work unravels the microscopic origin of the higher catalytic capacity of copper Sigma 5(310) grain boundary which can be helpful to guide the development of novel Cu-based catalysts for higher alcohol formation from syngas. (C) 2015 Elsevier B.V. All rights reserved.