Long-term stable and selective conversion of carbon dioxide to formate using dental amalgam electrode

Abstract

The process of electrochemical conversion of CO2 to a valuable chemical requires the use of an electrode material with high selectivity and stability. In this study, we successfully fabricated a dental amalgam composition on a copper foam electrode and demonstrated the selective conversion of CO2 to formate. The faradaic efficiency was 80–100 % at current densities ranging from 50 to 250 mA∙cm−2. The residual electricity was used solely to produce H2, and all the carbon atoms in CO2 were converted to formate. It enabled the easy separation of the highly water-soluble formate from the gaseous hydrogen. The produced formate concentration was up to 2.4 M (18 wt%), and the electrolyzer based on the dental amalgam electrode was effectively operated both continuously and intermittently for over a month. The results demonstrated the feasibility of the economic and large-scale CO2-to-formate conversion process.