A cobalt-free Pr6O11–BaCe0.2Fe0.8O3-δ composite cathode for protonic ceramic fuel cells with promising oxygen reduction activity and hydration ability

Oxygen reduction and proton conduction originated from hydration are two key steps in the cathode process of protonic ceramic fuel cells. In this work, Pr 6 O 11 is impregnated into a cobalt-free BaCe 0.2 Fe 0.8 O 3-δ cathode, resulting in an improved activity of lattice oxygen and a moderate enhancement of the electrical conductivity, both of which are beneficial for charge transfer, the rate-determining step of oxygen reduction process at the cathode. The polarization resistance of bare BaCe 0.2 Fe 0.8 O 3-δ cathode for oxygen reduction is 0.115 Ω cm 2 at 700 °C, which is reduced significantly to 0.039 Ω cm 2 with the addition of 30 wt% Pr 6 O 11 . Besides, the hydration ability of the cathode is also improved with Pr 6 O 11 , and thus the combination of proton and oxygen is facilitated. A single cell with 30 wt% Pr 6 O 11 -70 wt% BaCe 0.2 Fe 0.8 O 3-δ composite cathode exhibits the highest maximum power density of 1406 mW cm −2 at 700 °C. The composite cathode also shows a good stability.