Theoretical computation of C–C coupling reactions by different C1 intermediates at Cun and Cun−1Ag clusters supported on TiO2

Abstract

*CO dimerization is a well-known pathway for C–C bond formation, producing C₂₊ products. However, the mechanisms of C–C coupling between other C₁ intermediates remain less explored. In this study, we investigate C–C bond formation involving *CO, *CHO, *COH, and other C₁ intermediates on Cu_n and Cu_n−1Ag clusters supported on TiO₂. Interestingly, our results reveal that the activation energy for *CO dimerization is not the lowest, indicating that it is not the dominant pathway for C–C bond formation. Coupling reactions involving *CHO, *COH, and other C₁ intermediates exhibit lower activation energies. Furthermore, the activation energy for the same reaction varies across different Cu_n clusters, emphasizing the role of cluster selection in C–C coupling. Notably, on certain clusters, such as Cu₈, the activation energy for C–C bond formation at the Ag site is lower than that at the Cu site, suggesting that Ag doping can enhance C–C coupling. However, in larger clusters like Cu₁₃, the activation energy at the Ag site exceeds that at the Cu site, highlighting that the effect of Ag doping is cluster size dependent. This study provides new insights into C–C bond formation, offering guidance for designing efficient co-catalysts to produce high-value C₂₊ products.