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

Abstract

A tubular type solid oxide cell which consists of a NiO-Y 2 O 3 stabilized ZrO 2 (YSZ) tubular cathode substrate, a La 0.9 Sr 0.1 Ga 0.8 Mg 0.2 O 3−δ (LSGM) electrolyte film and a Sm 0.5 Sr 0.5 CoO 3-δ (SSC) anode was prepared by dip-coating for CO 2 electrolysis at 800 °C. Since Ni in Ni-YSZ substrate is easily re-oxidized under a pure CO 2 electrolysis atmosphere, co-feeding a reductive gas was essential for avoiding Ni re-oxidation and achieving a stable and large CO 2 electrolysis current under high temperature operation. It was found that co-feeding H 2 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 H 2 was used as a reductive gas. Deposition of a thin Ni-Fe cathode active layer and CeO 2 nano-particles obtained by infiltration were effective for increasing the CO 2 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 CO 2 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 CO 2 electrolysis, when 10% or 5% of CO was co-fed.