Experimental Characterization and Theoretical Modeling of Methane Production by H₂O/CO₂Co-Electrolysis in a Tubular Solid Oxide Electrolysis Cell

Methane production by H 2 O/CO 2 co-electrolysis in solid oxide electrolysis cells (SOECs) is a promising method to store unstable renewable power and to reduce CO 2 emission. In this paper, the CH 4 synthesis characteristics in tubular SOECs (TSOECs) is studied by experiments and numerical simulation in the temperature range of 550–650°C. The experimental results show that the addition of H 2 into the cathode inlet gas flow and the increase of electrolysis current could significantly promote CH 4 production rate. In the case of the experiments without H 2 , the CH 4 production ratio increased by less than 0.04% when the operating voltage varied from OCV to 1.5 V. After feeding the H 2 into the cathode atmosphere, the CH 4 production ratio increases by 3–4%. A CH 4 yield of 9.94% and a CH 4 production ratio of 12.34% were achieved at 550°C with 20% H 2 fed into cathode and an applied voltage of 1.5 V. Finally, a theoretical model is developed by considering the chemical/electrochemical reaction and transport processes, and the thermal distribution and optimal operating condition of the TSOEC are studied. An designed thermal distribution in counter-flow mode with lower inlet steam partial pressure could dramatically improve the CH 4 production.