Wet-air co-electrolysis in high-temperature solid oxide electrolysis cell for production of ammonia feedstock

Abstract

To significantly abate the carbon footprint in the conventional Haber-Bosch process, a novel approach based on wet air co-electrolysis in solid oxide electrolysis cell (SOEC) was proposed and evaluated in this study for sustainable single-step production of ammonia feedstock (i.e., H2/N2 mixture). An electrolyte-supported SOEC composed of LSCM-GDC cathode, SSZ electrolyte and LSCF-GDC anode was prepared and tested under various operation conditions. The current-voltage responses measured for wet air co-electrolysis were featured with three different regions which could be attributed to competitive and combinative effects of oxygen splitting reaction and water splitting reaction under wet air co-electrolysis operation. Gas chromatography (GC) analysis of the exit gas from the cathode chamber proved that high purity H2/N2 mixture had been produced successfully through the novel wet air co-electrolysis process. However, the obtained H2:N2 ratios were still much lower than the desired 3:1 ratio in the ammonia feedstock for the Haber-Bosch process. Further explorations will be made to increase the H2:N2 ratio in the produced gas mixture.