Alternative Cathode Material for CO2 Reduction by High Temperature Solid Oxide Electrolysis Cells

Three different cathode materials for CO2 reduction by high temperature solid oxide electrolysis cell were employed and compared in different CO2/CO atmospheres. The I-V curves showed distinct non-linear behavior in humidified 5% H-2/Ar atmospheres and closer to linear responses in CO2/CO atmospheres. Different impedance responses were found on these cathodes for CO2 electrolysis, suggesting different rate-limiting processes occurred. The polarization resistance, Rp, of Ni/YSZ cathode first reduced and then increased with increasing CO concentration, possibly because of coke formation at high CO content, which was not observed on LSCM based cathodes. Compared to the LSCM/YSZ cathode, the LSCM/GDC cathode had larger Rp at OCV but lower Rp under load probably due to the reduction of GDC which enhanced the cathode activity. The LSCM/GDC cathode also showed good durability in CO2 electrolysis operation, indicating a promising alternative cathode for CO2 electrolysis. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.040208jes]