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

Abstract

Density functional theory is employed to investigate the Fischer–Tropsch mechanism on copper ∑5(310) tilt grain boundary together with Cu(111) surface. For the methanol formation, Cu∑5(310) can effectively reduce each energy barrier through the preferred CH3O intermediate route as compared with Cu(111). Furthermore, Cu∑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∑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 CO bond scission. The adaptive character of ∑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 ∑5(310) grain boundary which can be helpful to guide the development of novel Cu-based catalysts for higher alcohol formation from syngas.