CO₂ adsorption enhancement and charge transfer characteristics for composite graphene doped with atoms at defect...

The massive emission of carbon dioxide in the world causes global warming and a series of increasingly serious ecological problems. It is urgent to find efficient adsorbent for large-scale CO₂ capture. Graphene as a solid adsorbent has exhibited great potential and development prospects in gas adsorption. Doping atoms at defect sites in composite graphene is considered as one of the promising approaches to enhance the gas adsorption ability. Nevertheless, composite graphene doping with different atoms has not been explored to a large extent so far.

In this work, vacancy graphenes with single C-vacancy (VI-G) and with double C-vacancies (VII-G) are doped with nitrogen atoms and metal atoms M (M = Co, Mo, Mn, Fe) to form composite configurations. The Perdew-Burke-Ernzerho (PBE) functional is used under the generalized gradient approximation (GGA) basis set. A comprehensive study of the adsorption effect and charge transfer characteristics of CO₂ molecule on different composite graphene configurations is carried out through DFT calculation. By analyzing the adsorption energy, adsorption distance, energy band structure, and atomic Mulliken population, it is found that the composite graphene doped with metal atoms such as Co-3N-VI, Mo-3N-VI, Mn-3N-VI, Fe-3N-VI, and Mo-4N-VII significantly enhanced the CO₂ adsorption. Further analysis of charge density and density of states (DOS) demonstrates that CO₂ adsorption on M-3N-VI and M-4N-VII reached the same conclusion. Thus, it is concluded that appropriate metal atoms can enhance the adsorption characteristics.