Near 100% CO2 conversion and CH4 selectivity in a solid oxide electrolysis cell with integrated catalyst operating at 450 °C

Direct methanation of CO2 feed within a solid oxide electrolysis cell (SOEC) has been demonstrated in the literature H2O splitting, CO2 reduction, and the reverse water-gas shift are identified as the typical reaction principles that occur over an SOEC cathode. The introduction of a methanation catalyst component further shifts the product stream from syngas to methane. The high SOFC operating temperature and lack of effective catalyst implementation methods attributed to relatively low influent conversion and methane yield in the literature. Two new catalyst implementation design strategies are proposed in this article. These strategies, along with proper selection of reaction conditions, have led to near 100% CO2 conversion and near 100% CH4 selectivity at 450 °C for a CO2/H2O/H2 feed over an yttria-stabilized zirconia (YSZ)-based SOEC cathode. Thermodynamic modeling indicates that the optimal configuration allows the system to reach thermodynamic equilibrium. Electrochemical testing confirmed that the cell function was not inhibited by these specific catalyst implementation methods. This report highlights how optimizing operation conditions (temperature/feed/etc) and catalyst implementation lead to highly efficient methanation under conditions relevant to low temperature SOEC function.