Acceleration of electrochemical CO₂ reduction to formate at the Sn/ reduced graphene oxide interface

Electrochemical CO₂ reduction is a key technology to recycle CO₂ as a renewable resource, but adsorbing CO₂ on the catalyst surface is challenging. We explored the effects of reduced graphene oxide (rGO) in Sn/rGO composites and found that the CO₂ adsorption ability of Sn/rGO was almost 4-times higher than that of bare Sn catalysts. Density functional theory calculations revealed that the oxidized functional groups of rGO offered adsorption sites for CO₂ toward the adjacent Sn surface and that CO₂-rich conditions near the surface facilitated the production of formate via COOH* formation while suppressing CO* formation. Scanning electrochemical cell microscopy directly indicated that CO₂ reduction was accelerated at the interface, together with the kinetic suppression of undesirable and competitive hydrogen evolution at the interface. Thus, the synergism of Sn/rGO ensures a substantial/rapid supply of CO₂ from the functional groups to the Sn surface, thereby enhancing the Faradaic efficiency 1.8-times compared with that obtained with bare Sn catalysts.