The spontaneous electrochemical reduction of gaseous CO2 using a sacrificial Zn anode and a high-surface-area dendritic Ag-Cu cathode

Abstract

Carbon dioxide (CO2) has been considered as a green-house gas that causes environmental problems of global warming. On the other hand, the CO2 is a sustainable carbon feedstock, which can be used for the production of value-added products. With rising levels of CO2 in atmosphere, methods capable of converting CO2 into value-added products have become more important. Among several methods, the electrochemical CO2 reduction has attracted much interest because it can alter CO2 to other useful compounds even at relatively low temperatures. In most previous works, the electrochemical reduction of CO2 has occurred only when the cathodic overpotential has been applied in aqueous electrolyte system. In such a system, the continuous electric power has to be supplied and the amount of CO2 delivery has been also limited. In this work, we have designed the gaseous CO2 reduction system using sacrificial zinc anode and dendritic silver-copper cathode. Considering that the standard reduction potential of zinc is further negative than that of CO2, the system has been operated spontaneously, in which the Zn electrode is readily oxidized to Zn(OH)42- ion and gaseous CO2 is reduced. During the spontaneous operation of the system, the power density of 14.97 mW/cm2 has been obtained with the production of carbon monoxide and hydrocarbons such as CH4, C2H4, and C2H2.