Limitations and trends on cobalt-free cathode materials development for intermediate-temperature solid oxide fuel cell- an updated technical review

Intermediate-temperature solid oxide fuel cell (IT-SOFC) work at moderate temperature range (600—800 ℃), thereby eliminating the issue of thermal degradation of electrode materials, reduce operational cost, increase flexibility of material selections, and enhance electrochemical stability of cell components. At intermediate-temperature range, there exists sluggish cathodic reaction, high activation energy and slow oxygen reduction reaction (ORR) at the cathode. Several cobalt-containing cathode perovskite materials with mixed ionic and electronic properties have been developed, which has helped in resolving sluggish ORR and enhances cathodic reaction, thereby increasing the overall performance of IT-SOFC. The expensive nature of cobalt, high evaporation rate and poor thermal expansion coefficient (TEC) means cobalt-free cathode materials need to be investigated. The present study gives an insight into the current trends of cobalt-free cathode materials development in IT-SOFC. Literature reviewed showed composite La0.65Ca0.35FeO3-δ-Gd0.2Ce0.8O2-δ (LCF-GDC), and La0.7Sr0.3Cu0.15Fe0.85O3-δ cathode materials has good polarisation resistance of 0.28 Ωcm2 at 750 ℃, and 0.0153 Ωcm2 at 700 ℃, respectively. Limitations, challenges, gaps were identified, and possible future research direction was recommended. The study also analysed the use of symmetrical electrodes, as it will help resolve the complexity of developing different electrode materials for cathode and anode in IT-SOFC. Holistic efforts were devoted to ensuring that the literature reviewed was recent (within the last 4yrs), and relevant to the current constraints impeding cathode materials use in IT-SOFC. This review study is meant to serve as a reference material to related researchers, and industry experts looking for the most recent accomplishments in cobalt-free cathode materials development.