Enhanced oxygen reduction reaction activity of BaCe0.2Fe0.8O3-δ cathode for proton-conducting solid oxide fuel cells via Pr-doping

BaCe 0.2 Fe 0.8-x Pr x O 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 0.2 Fe 0.6 Pr 0.2 O 3-δ has the most adsorbed oxygen and Fe 3+ on the surface, resulting in the fastest oxygen surface exchange kinetics and the highest activity. The partial pressure of H 2 O 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 0.2 Fe 0.6 Pr 0.2 O 3-δ shows the lowest polarization resistance of 0.057 Ω cm 2 , 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 0.2 Fe 0.8 O 3-δ is a promising cobalt-free cathode material for proton-conducting solid oxide fuel cells.