Associative vs. dissociative binding of CO2 on M5 transition metal clusters

Reaction paths were calculated using Density Functional Theory for the reaction of carbon dioxide with a series of transition metal pentamers, M5 + CO2, (M = Nb, Mo, Ru, Rh, Pd, Ag, Pt). A stochastic search algorithm was used to identify geometries with intact CO2, as well as geometries where the CO2 molecule was partly (O + CO) and fully dissociated (O + C + O). Nb5and Mo5 clusters were found to thermodynamically dissociate CO2. Pd5 and Ag5 were found to leave the CO2 molecule intact, Ru5 could partly dissociate CO2, while for Rh5 and Pt5, the fate of the adsorbed CO2 was dependent on the cluster geometry. The change in the CO2 πu orbital energy in the capture species on initial reaction with the M5 cluster was found to distinguish clusters where CO2 fully dissociated, but could not distinguish clusters where CO2 was found to partly dissociate