In-silico study of the adsorption of H2, CO and CO2 chemical species on (TiO2)n n=15-20 clusters: The (TiO2)19 case as candidate promising

In order to obtain an adsorption tendency of H-2, CO and CO2 molecules on (TiO2)n n = 15-20 clusters, DFT calculations were carried out to evaluate the interaction among these systems. The (TiO2)19 cluster emerges as the best candidate to storage these chemical species. Then, two adsorption sites were considered to attach these molecules onto (TiO2)19 cluster: through of surface formed by i) titanium and ii) oxygen atoms, respectively. The adsorption energy values are more favored for case 1 than the case 2, due to short distances between titanium atom and these chemical species. In this sense, the larger values of chemisorption are related to great decreasing of values of vibrational modes for gases isolated respect to those bonded to bare cluster. In general, the values of electronic gap do not suffer drastic changes, however the HOMO iso-surfaces are displayed in different way for both cases, and LUMO is located at center of cluster for the whole set of systems analyzed in this study. The electronic transference occurs from chemical species toward atoms at adsorption site, in all systems. These results reveal that this (TiO2)19 cluster is good candidate to storage or sense different kind of gases; thereby, this system can be used as a hydrogen storage device for energy green applications.