Pristine and Cu-decorated ψ-graphene-based materials for CO2 activation: A DFT(D)+ U Study

Capturing and repurposing anthropogenic carbon dioxide (CO2) is the traditional way to deal with climate change and lack of fossil fuel. CO2 adsorption (reduction) is the first step in this process. We have employed density functional theory-based calculations to investigate CO2 activation over the pristine and Cu-decorated carbon-based two-dimensional ψ-graphene material and its hydrogenated forms, i.e., ψ-graphone (half hydrogenated) and ψ-graphane (fully hydrogenated). ψ-graphene is a metallic allotrope of graphene containing 5-6-7 membered carbon rings. Our study found exothermic binding of CO2 with all three materials (for both pristine and Cu-decorated materials), indicating spontaneous physisorption. The presence of single atoms of the transition metal plays a significant role in increasing the activity of materials towards CO2 activation. We observed that the adsorption energy increases about three times after decorating a ψ-graphene sheet with Cu atoms. In contrast, no significant variation is observed on ψ-graphone or ψ-graphane materials. Our Bader charge analysis confirms the charge transfer from 2d nano-sheets to the molecule, where the values of calculated adsorption energies and the density of states suggest that the interaction between CO2 and these three materials can be categorized as weak physisorption., while Cu decoration enhances the CO2 adsorption.