Investigation of limiting H2O/CO2 co-electrolysis to convert renewable electricity into chemical energy using solid oxide electrolysis cell

H2O/CO2 co-electrolysis offers an efficient way to convert renewable electricity into chemical energy. However, carbon deposition is a serious problem for H2O/CO2 co-electrolysis. In this work, limiting electrolytic potential, limiting electrolytic voltage and conversion ratios of H2O/CO2 co-electrolysis are investigated. At low temperatures, the limiting potential of H2O/CO2 co-electrolysis is low and the conversion ratio cannot reach high because solid carbon is easily formed through CO electrolysis or disproportionation reactions. At high temperatures, the electrolytic voltage and conversion ratios of H2O and CO2 can reach high because CO electrolysis or disproportionation reactions are not easy to take place. The conversion ratios of CO2 and H2O can reach 99.6 % and 99.4 % at the H2O/CO2 ratio of 1:1 and 1273 K without solid carbon formation. The polarization resistance of fuel electrode has different effects on the conversion ratios of CO2 and H2O under different conditions, which is obvious at low temperatures and high polarization resistance of fuel electrode. The conversion ratios of CO2 and H2O under limiting electrolysis condition decrease from 9.8 % to 36.6 %–1.8 % and 8.5 % when the polarization resistance of fuel electrode increases from 0 to 0.1 Ω cm2 at the H2O/CO2 ratio of 1:2 and 773 K.