Cooperative CO2 capture via oxalate formation on metal-decorated graphene

CO2 capture using carbon-based materials, particularly graphene and graphene-like materials, is a promising strategy to deal with CO2 emissions. However, significant gaps remain in our understanding of the molecularlevel interaction between CO2 molecules and graphene, particularly in terms of chemical bonding and electron transfer. In this work, we employ random structure search and density functional theory to understand the adsorption of CO2 molecules on Ca-, Sr-, Na-, K-, and Ti-decorated graphene surfaces. Compared to the pristine material, we observe enhanced CO2 adsorption on the decorated graphene surfaces. Particularly on group 2 metals and titanium-decorated graphene, CO2 can be strongly chemisorbed as a bent CO2 anion or as an oxalate, depending on the number of CO2 molecules. Electronic structure analysis reveals that the adsorption mechanism involves a charge transfer from the metal adatom to the adsorbed CO2. Overall, this study suggests that reducing CO2 to oxalate on group 2 metals and titanium-decorated graphene surfaces is a potential strategy for CO2 storage.