Theoretical study on the effect of H2O and ionic liquid on CO2 reduction on Cu surface

Abstract

Electrolyte plays a vital role in the CO₂ reduction on metal surface. The aqueous solutions of ionic liquids (ILs) as electrolytes have been demonstrated to be more efficient for CO₂ reduction compared to pure ionic liquid. We investigated the effect of H₂O and ILs ([Emim][PF₆], [Pmim][PF₆] and [Bmim][PF₆]) on CO₂ activation on Cu surface. CO₂ prefers to interact with ILs by cation alkyl and anion, and the interaction is stronger than that between CO₂ and H₂O. On Cu surfaces, the physical adsorption energy of CO₂ co-adsorbed with H₂O is close to that co-adsorbed with ILs due to the change of interaction pattern of CO₂ with ILs. H₂O and ILs can both be beneficial to the CO₂ reduction. However, H₂O plays more important for CO₂ activated adsorption and reduction reaction. ILs can significantly enhance the solubility of CO₂ in electrolyte.