Insight into size dependence of C2 oxygenate synthesis from syngas on Cu cluster: The effect of cluster size on the selectivity

Abstract

Size dependence of C2 oxygenate formation from syngas on Cu cluster has been investigated to qualitatively probe into the effect of Cu cluster size on the selectivity of C2 oxygenates, which includes two key steps: CHx and C2 oxygenate formations; Cu13, Cu38 and Cu55 clusters have been employed to model different sizes of Cu cluster. Here, density functional theory method has been performed. Our results show that the adsorption ability of the species involving in C2 oxygenate formation decreases with the increasing of Cu cluster size; Cu cluster size significantly affects the dominant existence forms of CHx(x=1–3) species and C2 oxygenates. Among three Cu clusters, Cu13 cluster exhibits the highest selectivity toward C2 oxygenates compared to other two clusters, suggesting that Cu cluster size can affect the selectivity toward C2 oxygenates, moreover, the smaller Cu cluster size is, the higher the selectivity of C2 oxygenates is. That is probably related to the high concentration of low-coordinated defect sites on small size Cu cluster, which results in the higher activity and selectivity toward C2 oxygenates. The identification of higher intrinsic selectivity of C2 oxygenates, active sites, and stronger cluster size effect would be valuable for developing more efficient and stable Cu catalyst with higher selectivity toward C2 oxygenate in syngas conversion.