Progress in Electrochemical CO2 Reduction in Gas Phase – Design of Efficient Co-Electrolyser Systems

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The electrochemical CO2 reduction reaction (CO2RR) is a complex reaction which must be carried out in a highly selective and efficient manner. Many efforts are being taken to develop catalysts with improved reaction selectivity and efficiency and significant progress has been made in this area of research [1]. However, CO2RR kinetics, product identification and quantification are mostly carried out in half-cell configurations using liquid electrolytes. This fundamental approach of studying CO2RR is limited by the low solubility of CO2 in water, the maximum CO2 reduction current reported in the literature is in the range of 0.01- 0.02 A/cm2 [2]. In order to overcome the solubility problem and to reach higher operating current densities, CO2 reduction can be carried out in a co-electrolysis system where pure or diluted gaseous CO2 is used. Our research efforts were focused on the design of an electrochemical cell for co-elecrolysis operating at high-current densities with good product selectivity. The most promising results were obtained when a bipolar membrane was used as the electrolyte. The experiments were conducted in a membrane electrolyzer-like configuration setup. Various gold type cathode electrode materials were tested. IrTiO2 was used as an anode material to catalyse the oxygen evolution reaction. The reaction products were analysed by on-line mass spectroscopy. The co-electrolyser performance and the selectivities of the various MEAs are examined in detail.