Enhanced oxygen reduction reaction activity of Ca doping CoFe2O4 as cathodes for solid oxide fuel cells

CoFe 2 O 4 (CFO) was identified as one of the potential cathode materials for solid oxide fuel cells (SOFCs). However, optimization was required due to limitations of electrochemical performance. Here effects of Ca doping on CFO were investigated for the oxygen reduction reaction (ORR) properties. Co 1-x Ca x Fe 2 O 4 (CCxFO, x = 0, 0.2 (CC2FO), 0.4 (CC4FO)) were synthesized with sol-gel method. Oxygen vacancy concentration was increased by Ca doping enhancing the electrochemical performance of CFO. At 750 °C, the polarization resistance (R p ) of CC4FO was 1.04 Ω·cm 2 , which was 1.09 Ω·cm 2 lower than that of CFO (2.13 Ω·cm 2 ). The electronic conductivity value (σ) of CC4FO was 0.614 at 750 °C and the activation energy (E a ) of CC4FO was 102.81 kJ/mol. The results indicated that improvements in the ORR activity of the CFO spinel material were mainly attributed to an increase in oxygen vacancy concentration and oxygen surface exchange rate due to Ca doping, CC4FO showed promising potential as SOFC cathode.