Insight into the Preference Mechanism of CHx (x=1-3) and C-C Chain Formation Involved in C2 Oxygenate Formation from Syngas on the Cu(110) Surface

The possible formation pathways of CHx (x = 1-3) and C-C chain involved in C-2 oxygenate formation from syngas on an open Cu(110) surface have been systematically investigated to identify the preference mechanism of CHx (x = 1-3) and C-C chain formation. Here, we present the main results obtained from periodic density functional calculations. Our results show that all CHx (x = 1-3) species formation starts with CHO hydrogenation; among them, CHx (x = 2, 3) are the most favored monomers, however, CH3OH is the main product from syngas on the Cu(110) surface, and the formation of CHx (x = 1-3) cannot compete with CH3OH formation. Further, on the basis of the favored monomer CHx (x = 2, 3), we probe into the C-C chain formation of C-2 oxygenates by CO or CHO insertion into CHx (x = 2, 3), as well as the hydrogenation, dissociation, and coupling of CHx (x = 2, 3), suggesting that CO insertion into CH2 to form C-2 oxygenates is the dominant reaction for CH2 on the Cu(110) surface with an activation barrier of 44.5 kJ.mol(-1); however, for CH3, CH3 hydrogenation to CH4 is the dominant reaction on the Cu(110) surface with an activation barrier of 67.5 kJ.mol(-1). As a result, to achieve high productivity and selectivity for C-2 oxygenates from syngas, Cu has to get help from the promoters, which should be able to boost CH2 formation and/or suppress CH3OH and CH3 formation. The present study provides the basis to understand and develop novel Cu-based catalysts for C-2 oxygenate formation from syngas.