Comparative computational study of CO2 hydrogenation and dissociation on metal-doped Pd clusters

Density functional theory calculations are executed to research CO2 adsorption and initial conversion on Pd12M (M = Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd) bimetallic clusters, with a focus on finding optimal ancillary metal to Pd element. The stability analysis of the structures demonstrates that the transition metals with higher surface energy (compared to Pd element) doped Pd13 clusters possess better structural stability. For CO2 adsorption, the structural parameters of CO2* have remarkable linear relation with the amount of charges transfer. For CO2 initial conversion, it can be concluded that the Pd12Cu cluster is the best candidate with a lower activation barrier (0.69 eV) for the initial hydrogenation of CO2. According to the electronic structure analysis, the elevated HOMO caused by the doping of Cu atom is the main reason for the enhanced catalytic activity. In addition, the PdCu bimetallic clusters with larger size are constructed and their activity and selectivity towards CO2 initial conversion are also studied. Compared with Pd32Cu6 and Pd42Cu13 bimetallic clusters, Pd12Cu has more advantages in activity and selectivity. Therefore, Pd12Cu is the best choice, that is, it inhibits the generation of by-product and improves the catalytic activity, which makes it become an excellent bimetallic candidate for CO2 initial hydrogenation.