CO2 electroreduction in aqueous and acetonitrile solutions on porous cathode fabricated by anode dezincification of CuZn

Abstract

The rates of the CO2 electrochemical reduction were determined on porous cathodes formed by electrochemical dealloying of CuZn under different regimes of selective anodic dezincification of brass. It was established that the formation of a porous surface proceeds in two following stages: 1) the dissolution of Zn from the CuZn mainly along the grain boundaries with the formation of submicron crevices between them, and 2) electrochemical dezincification of brass grains and formation of nanopores. The zinc content in the nanoporous copper surface is less than 1%. It was proved that anodically dezincified brass porous cathodes demonstrate a significantly higher CO2 reduction current on their surface than smooth copper and brass surfaces. For instance, in aqueous solutions, at an electrode potential of –1.5 V, the value of cathode current density on porous Cu cathodes is between 5 to 9 mAcm–2, while it is only 2.5 and 1.5 mAcm–2 on smooth Cu and CuZn cathodes, respectively. A similar trend is observed in an acetonitrile environment, where the current density of the CO2 electroreduction at the electrode potential of –3.0 V is 22 to 27 mAcm–2, 15 mAcm–2, and 18 mAcm–2 on porous cathodes, Cu cathode, and CuZn cathode, respectively. As the pore size decreases from submicron to submicron-nanosized, there is a tendency for an increase in cathodic currents by approximately 80% and 25% in aqueous and in acetonitrile solutions, respectively. Additionally, CO2 recovery on porous cathodes remains stable during long-term electrolysis at an electrode potential below –1.5 V.