CO2 adsorption and activation over medium sized Cun (n = 7, 13 and 19) clusters: A density functional study

First-principle calculations have been carried out to investigate the activation and adsorption of CO2 over Cun clusters. The structural and electronic properties like optimized geometries, HOMO–LUMO energy levels, binding energy per atom (BE/n), adsorption energy (Ead), natural electronic configuration using NPA analysis and density of states (DOSs) of the pure Cun and CunCO2 clusters in their ground state are thoroughly analyzed. Our results provide sound evidence for chemisorption and activation of CO2, on Cun (n = 7, 13, and 19) clusters with C–O bond stretched up to 1.20–1.30 Å. The positive adsorption energy for CO2 adsorbed on the Cun clusters suggests that the adsorption process is thermodynamically favorable. We find that the CO2 molecule, when adsorbed on one of the vertices of the icosahedral Cu13 cluster, has maximum adsorption energy (52.47 kcal mol−1) and acts as a precursor to dissociate it into CO and atomic oxygen. The preferential adsorption sites for CO2 molecule have been identified. The interaction between Cu cluster and CO2 molecule that leads to the formation of the CO 2 δ - species has been understood in terms of charge transfer using NPA analysis.