Electrochemical Conversion of Carbon Dioxide to Formate in Alkaline Polymer Electrolyte Membrane Cells

This paper is about the continuous electrochemical conversion of carbon dioxide to formate in a polymer electrolyte membrane cell using an alkaline ion-exchange membrane sandwiched between two catalyzed electrodes. This type of cell configuration allows carbon dioxide conversion to occur at high efficiencies and is particularly attractive for large-scale implementation. Formate was produced at high efficiency, and hydrogen evolution was suppressed with lead and indium as catalysts. The production of formate was monitored by UV-visible spectroscopy. During short experimental runs, the faradaic efficiency of formate production was as high as 80%. The faradaic efficiency was strongly dependent on the concentrations of carbon dioxide, bicarbonate, and carbonate at the surface of the electrodes. Low concentrations of carbon dioxide in the reactant feed led to the mass transport limitations and hence low faradaic efficiencies. The results show that mass transport limitations can be mitigated and high efficiencies can be realized by conducting the electrolysis in a pulsed mode. An alkaline membrane-based flow cell that ensures abundant availability of carbon dioxide to the electrodes can be a cost-effective and efficient approach for the continuous production of fuels from sunlight, storing of renewable energy, and lowering carbon dioxide levels in the atmosphere. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3526312] All rights reserved.