Simultaneous Electrochemical Reduction of Carbon Dioxide and Partial Oxidation of Methane in a Solid Oxide Cell with Silver-Based Cathode and Nickel-Based Anode

Abstract

Simultaneous electrochemical reduction of CO2 and partial oxidation of CH4 in a solid oxide cell (CO2/CH4 redox SOC) with Ag-based cathode and Ni-based anode is compared with CO2 reduction in a solid oxide electrolysis cell (CO2-SOEC) and CH4 oxidation in a solid oxide fuel cell (CH4-SOFC). Overpotential losses from different sources and gases products from each electrode are analyzed. Results show that the process of a CO2/CH4 redox SOC is exactly a combination of the cathode process of a CO2-SOEC and the anode process of a CH4-SOFC. With the same CO and syngas obtained, a CO2/CH4 redox SOC consumes less energy because it avoids oxygen evolution reaction (OER) of a CO2-SOEC and oxygen reduction reaction (ORR) of a CH4-SOFC. At 500 mA cm−2, the overall resistance of an electrolyte-supported CO2/CH4 redox SOC is only half of that for separately reducing CO2 in an SOEC and oxidizing CH4 in an SOFC. The conversion of CH4 and yield of H2 in the SOC approach 81% and 63%, respectively. An anode-supported CO2/CH4 redox SOC is operated stably for 110 h at 1 A cm−2 under an applied voltage of ∼0.9 V. Sufficient current density may prevent high performance Ni-based anode from coking.