Multiple CO2 capture in stable metal-doped graphene: a theoretical trend study

Abstract

Identifying stable systems with high CO₂ adsorption capacity is an essential goal in CO₂ capture and storage technologies. We have carried out a comprehensive first-principles study to explore the CO₂ capture capacity of 16 representative metal-doped graphene systems where the metal dopants can be stabilized by single- and double-vacancies. The maximum number of adsorbed CO₂ molecules was determined by a combination of adsorption energy and bond distance criteria. Generally, while the double-vacancy can bind metal dopants more strongly than the single-vacancy, single-vacancy graphene with metal dopants are better sorbents, with each Ca, Sc and Y dopant binding up to 5 CO₂ molecules. CO₂ capture involves significant charge transfer between the CO₂ molecule and the dopant–vacancy complexes, where defective graphene acts as a charge reservoir for binding CO₂ molecules. Some systems are predicted to involve the formation of a bent CO₂ anion. Ca-doped single- and double-vacancy graphene systems, however, readily form oxides upon reaction with CO₂, thus they are less reusable for CO₂ capture.