Near 100% CO2 conversion and CH4 selectivity in a solid oxide electrolysis cell with integrated catalyst operating at 450 °C. (May 2022)

• Record Type: Journal Article
• Authors: Baxter, Samuel J.; Rine, Miranda; Min, Byunghyun; Liu, Ying; Yao, Jianhua
• Is Part Of: Journal of CO₂ utilization. Volume 59(2022)
• Publication Date: 2022-05
• Subjects: Solid oxide electrolysis cell -- Catalysis -- Methanation -- CO2 reduction; Carbon dioxide -- Periodicals; Carbon dioxide -- Environmental aspects -- Periodicals; Carbon dioxide mitigation -- Periodicals; Carbon dioxide; Carbon dioxide -- Environmental aspects; Carbon dioxide mitigation; Periodicals; 628.53205
• DOI: 10.1016/j.jcou.2022.101954
• Languages: English
• ISSNs: 2212-9820

Abstract

Abstract: Direct methanation of CO2 feed within a solid oxide electrolysis cell (SOEC) has been demonstrated in the literature H2 O 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 /H2 O/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. Graphical Abstract: A series of designs were investigated for the potential to exhibit a methanation function within the confines of a solid oxide electrolysis cell by direct implementation of a methanation catalyst. A hybrid design showcasing both an internal catalyst bed and a catalyst layer over the solid oxide electrolysis cell cathode showed the best results. Operation conditions are optimized to display maximum methanation of the cell effluent and thermodynamic calculations are used to check the experimental results. ga1 Highlights: Proper catalyst implementation and reaction conditions led to near 100% CO2 conversion and CH4 selectivity in an SOEC. Lower cell operating temperature and higher H2 -to-CO2 ratio in the feed gas facilitate the conversion. Thermodynamic modeling indicates that the optimal configuration allows the system to reach thermodynamic equilibrium. Test results confirmed that the cell function was not inhibited by these specific catalyst implementation methods.