Infiltrated nano-CeO2 and inserted Ni-Fe active layer in a tubular cathode substrate for high temperature CO2 electrolysis on solid oxide cells using La0.9Sr0.1Ga0.8Mg0.2O3−δ thin film electrolyte

A tubular type solid oxide cell which consists of a NiO-Y2O3 stabilized ZrO2 (YSZ) tubular cathode substrate, a La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) electrolyte film and a Sm0.5Sr0.5CoO3-δ (SSC) anode was prepared by dip-coating for CO2 electrolysis at 800 °C. Since Ni in Ni-YSZ substrate is easily re-oxidized under a pure CO2 electrolysis atmosphere, co-feeding a reductive gas was essential for avoiding Ni re-oxidation and achieving a stable and large CO2 electrolysis current under high temperature operation. It was found that co-feeding H2 is more effective for preventing re-oxidation of Ni compared with CO, however, the CO formation rate was slightly lower than that estimated amount by Faraday`s law due to a water shift reaction when H2 was used as a reductive gas. Deposition of a thin Ni-Fe cathode active layer and CeO2 nano-particles obtained by infiltration were effective for increasing the CO2 electrolysis current because of the decrease in the cathodic overpotential. In spite of the low concentration of Ce was infiltrated by using a 1 M solution with a dip process, the volume change in substrate caused by the CO2 oxidant was also measured. The CO formation rate almost corresponded to the amount estimated by Faraday`s law and the coke deposition was hardly observed in Ni-YSZ substrate after CO2 electrolysis, when 10% or 5% of CO was co-fed. © 2022