Multiple CO2 capture in pristine and Sr-decorated graphyne: A DFT-D3 and AIMD study

Recent advances in two-dimensional carbon allotropes and their applications as efficient CO2 capture materials can decrease effect of CO2 on the global weather changes. In current study, influence of strontium on the structural and electronic properties of a new allotrope of carbon, graphyne (GY), toward promotion of CO2 capture capacity were investigated using DFT-D3 calculations. Various sites for Sr decoration in GY frame were probed. Then, we investigated the best site and direction for adsorption of CO2 on the structures. Results show that the best site is 1.740 angstrom above the center of the 12-membered ring with the adsorption energy of - 3.034 eV. It is very more than bulk cohesive energy of Sr (about - 1.72 eV/atom), therefore, aggregation of the Sr atoms is hindered on the GY sheet. Also, for pristine GY, 12-membered ring and for Sr-decorated GY, top of Sr atom are the best sites for CO2 trapping with adsorption energies of - 0.252 and - 0.425 eV, respectively. Thermal stability of the structures at room temperature was confirmed by Ab initio molecular dynamics (AIMD) simulation. Adding of CO2 molecules on the pristine and Sr-decorated GY shows that three and seven CO2 molecules can adsorb on one side of the GY sheet with the average adsorption energy of - 0.260 and - 0.478 eV/CO2, respectively. Therefore, CO2 capture capacity is estimated to be as high as 31.68 wtWo for the Sr-decorated GY. This study shows that Sr-decorated GY can be used as a hopeful candidate for the CO2 capture applications in the future.