Nickel-doped NdBa0.5Sr0.5Co1.5Fe0.5O5+δ oxygen electrode material for high performance reversible protonic ceramic cells

To enhance the electrocatalytic activity in the oxygen reduction and the evolution reactions of air electrode materials, we fabricate a double perovskite structured NdBa0.5Sr0.5Co1.5Fe0.5-xNixO5+δ with triple-conducting properties for reversible protonic ceramic cells (RPCCs). In particular, Ni doping into B-site (of ABO3 perovskite structure) is used to tailor the surface properties and bulk diffusion of NdBa0.5Sr0.5Co1.5Fe0.5O5+δ perovskites. Among the various amounts of dopants, doping with 5 mol% Ni significantly increases the activity of oxygen electrodes in moist air, including the conductivity of protons and oxygen-ions. The area specific resistance (ASR) values of the NdBa0.5Sr0.5Co1.5Fe0.45Ni0.05O5+δ (NBSCFN5) electrode in the BaZr0.1Ce0.7Y0.1Yb0.1O3-δ electrolyte are 0.70 Ω·cm2 at 650 ℃. The electrical conductivity of NBSCFN5 is 423–714 S·cm−1 at the RPCCs operating temperature (500–700 ℃), which is significantly higher than that of the conventional perovskite air electrode materials. Furthermore, the ASR of the NBSCFN5 symmetrical cell decreases considerably from 9.02 to 6.86 Ω·cm2 in dry air to pH2O = 0.6 atm at 550 ℃, implying its excellent proton conduction. This suggests that NBSCFN5 is a promising air electrode material for next-generation high-performance RPCCs at lower temperatures.