ELECTROCHEMICAL BEHAVIOUR OF CO/CO2 GAS ELECTRODE IN MOLTEN ALKALI CARBONATES .I. EXPERIMENTAL TECHNIQUE AND THERMODYNAMIC RESULTS

The thermodynamic behaviour of the CO/CO2/Au electrode in molten alkali carbonate electrolyte was studied in a specially designed gas-tight apparatus. At temperatures 700-800°C, the equilibrium potential of this electrode was found to be determined by the over-all reaction CO + CO32- ⇄ 2CO2 + 2e-, and to obey the Nernst equation accurately over the whole range of gas compositions. A new CO/CO2/Au gas reference electrode was developed, and its zero potential defined by the condition (Pco2)2/pco = 1 atm. In relation to this reference electrode, a new potential scale for molten carbonate electrolytes is proposed. The implications of the Boudouard equilibrium are considered in relation to the CO/CO2 electrode, and a concept of the Equivalent Boudouard potential" is suggested. A convenient alignment chart constructed correlates directly all the relevant variables to the CO/CO2 potential expressed on the new standard scale. © 1968."