Investigate the proton uptake process of proton/oxygen ion/hole triple conductor BaCo0.4Fe0.4Zr0.1Y0.1O3-δ by electrical conductivity relaxation

The proton surface uptake kinetics of proton, oxygen ion and hole triple conductor BaCo0.4Fe0.4Zr0.1Y0.1O3-δ (BCFZY) is investigated by electrical conductivity relaxation method (ECR). The proton uptake process is controlled by changing the water partial pressure at constant temperature. And the proton concentration in BCFZY bulk could be calculated by the conductivity change value (Δσ: 0.063 Scm−1 at 500 °C) from 0% to 10% pH2O. The proton surface exchange coefficient, kδ is 3.85 × 10−6 cm−1 at 500 °C, derived from fitting the relaxation curve. It is also found the proton uptake reaction rate would be enhanced under higher oxygen partial pressure. And the kδ value could be greatly enhanced by one order of magnitude with doped ceria coated on BCFZY surface, which also proved that the proton uptake kinetics is limited by the surface exchange step. In all, this work provides an effective way to measure the proton surface exchange kinetic for proton conductive cathode.