Electrochemical decomposition of CO2 and CO gases using porous yttria-stabilized zirconia cell

Electrochemical decomposition of CO2 and CO gases using a porous cell of Ru-8 mol% yttria-stabilized zirconia (YSZ) anode/porous YSZ electrolyte/Ni–YSZ cathode system at 400–800 °C was studied by analyzing the flow rate and composition of outlet gas, current density, and phases and elementary distribution of the electrodes and electrolyte. A part of CO2 gas supplied at 50 ml/min was decomposed to solid carbon and O2 gas through the cell at the electric field strengths of 0.9–1.0 V/cm. The outlet gas at a flow rate of 3 ml/min included 61–63% CO2 and 37–39% O2 at 700–800 °C and the outlet gas at a flow rate of 50 ml/min included 73–96% (average 85%) CO2 and 4–27% (average 15%) O2 at 800 °C. On the other hand, the supplied CO gas was also decomposed to solid carbon, O2 and CO2 gases at 800 °C. The fraction of outlet gas at a flow rate of 50 ml/min during the CO decomposition at 800 °C for 5 h was 11–36% CO, 59–81% O2 and 2–9% CO2. The detailed decomposition mechanisms of CO2 and CO gases are discussed. Both Ni metal in the cathode and porous YSZ grains under the DC electric field have the ability to decompose CO gas into solid carbon and O2− ions or O2 gas.