Pressurized tubular solid oxide H2O/CO2 coelectrolysis cell for direct power-to-methane

To improve the energy-to-CH4 efficiency and enhance renewable power utilization, we investigate direct Power-to-Methane at low inlet H-2 content (25 vol%) in solid oxide electrolysis cell (SOEC). The synergy of the pressurized operation and the electricity input effectively enhances CH4 yield by one-order of magnitude from 2.8% to 28.7% and the CO2-to-CH4 ratio from 4.4% to 39.5% in the H-2-reduced case, where the ratio of H-2 consumption to total energy consumption decreases to 41% and the energy-to-CH4 efficiency increases to 53%. We develop a multiphysics tubular SOEC model to understand the intrinsic coupling between electrochemistry and heterogeneous catalytic chemistry. From the perspective of performance enhancement, geometry optimization, and thermal design, inhibiting CH4 production in the inlet gas-controlled zone and promoting CH4 production synergistically in both the electrochemistry-controlled zone and the temperature-controlled zone is the key to improve the energy-to-CH4 efficiency.