Abstract:
The energetic pathways of adsorption and activation of carbon dioxide (CO
2) on low-lying compact (TiO
2)
n clusters are systematically investigated by using electronic structure calculations based on density-functional theory (DFT). Our calculated results show that CO
2 is adsorbed preferably on the bridge O atom of the clusters, forming a "chemisorption" carbonate complex, while the CO is adsorbed preferably to the Ti atom of terminal Ti-O. The computed carbonate vibrational frequency values are in good agreement with the results obtained experimentally, which suggests that CO
2 in the complex is distorted slightly from its undeviating linear configuration. In addition, the analyses of electronic parameters, electronic density, ionization potential, HOMO-LUMO gap, and density of states (DOS) confirm the charge transfer and interaction between CO
2 and the cluster. From the predicted energy profiles, CO
2 can be easily adsorbed and activated, while the activation of CO
2 on (TiO
2)
n clusters are structure-dependent and energetically more favorable than that on the bulk TiO
2. Overall, this study critically highlights how the small (TiO
2)
n clusters can influence the CO
2 adsorption and activation which are the critical steps for CO
2 reduction the surface of a catalyst and subsequent conversion into industrially relevant chemicals and fuels.