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 molecular-level 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 the adsorption mechanism to involve an ionic 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 metal-decorated graphene surfaces is a potential strategy for CO₂ storage.