Tuning the defects of the triple conducting oxide BaCo0.4Fe0.4Zr0.1Y0.1O3-δ perovskite toward enhanced cathode activity of protonic ceramic fuel cells

Protonic ceramic fuel cells (PCFCs) have interesting potential to efficiently produce electrical power from fuels in a low-temperature range (<650 degrees C). However, the sluggish activity of the oxygen reduction reaction is one of the greatest obstacles to the development of PCFCs. Single-phase triple-conducting (e-/O2-/H+) oxides are considered to be the most promising candidates for highly active PCFC cathodes because they can extend the electrochemically active sites to the entire cathode surface. Here, A-site deficiency of perovskite is introduced to tune the triple-conducting properties, which can stimulate the generation of oxygen vacancies and increase the oxygen-ion bulk diffusion and proton hydration kinetics. The so-obtained A-site-deficient perovskite oxides, Ba<INF>x</INF>Co<INF>0.4</INF>Fe<INF>0.4</INF>Zr<INF>0.1</INF>Y<INF>0.1</INF>O<INF>3-delta</INF> (x = 1, 0.95, 0.9), exhibit area specific resistance values of 1.61, 0.94, and 0.52 omega cm2 for BaCo<INF>0.4</INF>Fe<INF>0.4</INF>Zr<INF>0.1</INF>Y<INF>0.1</INF>O<INF>3-delta</INF>, Ba<INF>0.95</INF>Co<INF>0.4</INF>Fe<INF>0.4</INF>Zr<INF>0.1</INF>Y<INF>0.1</INF>O<INF>3-delta</INF>, and Ba<INF>0.9</INF>Co<INF>0.4</INF>Fe<INF>0.4</INF>Zr<INF>0.1</INF>Y<INF>0.1</INF>O<INF>3-delta</INF>, respectively, at 500 degrees C in wet air (p<INF>H<INF>2</INF>O</INF> = 0.1 atm). Peak power densities of 797.47, 668.64, 548.07, and 376.27 mW cm-2 are obtained from the PCFC with the Ba<INF>0.9</INF>Co<INF>0.4</INF>Fe<INF>0.4</INF>Zr<INF>0.1</INF>Y<INF>0.1</INF>O<INF>3-delta</INF> cathode at 650, 600, 550 and 500 degrees C, respectively. Such remarkable performance demonstrates that introducing A-site deficiency is an effective strategy to enhance the triple-conducting properties of perovskite oxides for the high-activity cathode of PCFCs.