Adsorption of CO, CO2 and NO2 onto nanographenes (NGs), anchored systems as NG−(ZnO)n n = 1-6: An ab initio molecular dynamics calculations

To assess the chemical interaction between different gases and functionalized semiconductor clusters, DFT (Density functional theory) simulations were performed.

For this work the primary objective is to understand the behavior of nanographenes NGs →C (carbon atoms) functionalized with a cluster of zinc oxide (ZnO)_n of different sizes n = 1-6, to understand the effects of smallest clusters, hence it is important to stablish the adsorption tendency at first stages. This first step is the basis for evaluating the chemical interaction between CO, CO₂, and NO₂ with functionalized semiconductor clusters. The objective is to study changes in adsorption trends, considering different gases and clusters sizes.

The adsorption energy values for C-(ZnO)₂-CO, C-ZnO-CO₂ and C-ZnO-NO₂ are -0.195 eV, -0.543 eV and -3.042 eV respectively, which is related to the results of lower average length distance A.B.L. obtained between the atoms of the species studied (distance of Zn atom to CO, CO₂ and NO₂). Due to the active sites, there is presence of a chemisorption in C-ZnO-NO₂ system, but in C-(ZnO)₂-CO and C-ZnO-CO₂ present physisorption. The electron gap values do not vary significantly for n = 3-6 and the HOMO-LUMO isosurfaces are depicted for all systems. The electron transfer at the adsorption sites is directed from the chemical species toward the CO, CO₂, and NO₂ in all the systems analyzed. Based on these findings, C-(ZnO)₂-CO, C-ZnO-CO₂ and C-(ZnO)₁-NO₂ systems are potential options for CO, CO₂, and NO₂ gas storage, respectively. In addition, an analysis has been carried out on the behavior of larger GNs systems. These results may be useful to researchers in the potential design of a gas storage device for energy applications that are environmentally friendly.