Enhanced oxygen reduction reaction activity of BaCe_0.2Fe_0.8O_3-δ cathode for proton-conducting solid oxide fuel cells via Pr-doping

BaCe_0.2Fe_0.8-xPr_xO_3-δ (x = 0–0.3) is studied as a cobalt-free cathode material for proton-conducting solid oxide fuel cells. The cathode is composed of a cubic BaFeO_3-δ phase and an orthorhombic BaCeO_3-δ phase, and Pr is doped in both phases. The partial substitution of Pr for Fe decreases the content of the BaFeO_3-δ phase, leading to a lower electrical conductivity. BaCe_0.2Fe_0.6Pr_0.2O_3-δ has the most adsorbed oxygen and Fe³⁺ on the surface, resulting in the fastest oxygen surface exchange kinetics and the highest activity. The partial pressure of H₂O shows a negligible effect on the polarization resistance of the cathode. In contrast, the polarization resistance increases remarkably with the decrease of oxygen partial pressure, indicating that the rate of the cathode process is controlled by the surface exchange of oxygen. At 700 °C, BaCe_0.2Fe_0.6Pr_0.2O_3-δ shows the lowest polarization resistance of 0.057 Ω cm², and a single cell with that cathode exhibits the highest maximum power density of 562 mW cm⁻². The results demonstrate that Pr doped BaCe_0.2Fe_0.8O_3-δ is a promising cobalt-free cathode material for proton-conducting solid oxide fuel cells.