| Abstract | In this contribution, we studied electrochemical reduction of H₂O and CO₂ at reduced temperatures using anode supported SDC cells. We observed that the SDC cell voltage was 1.16 V under electrochemical reduction of H₂O and 1.17 V under electrochemical reduction of CO₂ at 500oC, 0.5 A cm⁻². The cell showed no degradation during a short term (72 hr) stability test under the CO₂ electrochemical reduction condition. It was noticed that the SDC cells showed much better cell performance in the electrolysis cell (EC) mode than in the fuel cell (FC) mode in term of polarization. It was also found that the impedance of the SDC cell changed dramatically with applied current. At high applied EC current the cell became more like a pure inductor (or a resistor), i.e., the semicircle representing the electrochemical polarization was decreased, and the electrolyte bulk resistance was also reduced substantially. It implies that the SDC cell under the EC mode becomes more electronically conductive, and the resistance is varied with the applied current. GC analysis of fuel side gas composition revealed that CO₂ conversion rate was low, and almost irrelevant to the applied current. The corresponding faradic efficiency is extremely low, indicating a severe internal shorting problem under the EC tested conditions. Therefore, we conclude that the anode supported SDC electrolyte cell is not feasible for SOEC application even at a reduced temperature. |
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