Attenuating a metal-oxygen bond of a double perovskite oxide: Via anion doping to enhance its catalytic activity for the oxygen reduction reaction

Elevating the sluggish oxygen reduction reaction (ORR) activity of the cathode material is crucial to the development and widespread application of intermediate-temperature solid oxide fuel cells (IT-SOFCs). Herein, a novel SOFC cathode, with superior ORR activity, is designed by incorporating F anions at O-sites of a double perovskite oxide (Sr2Fe1.5Mo0.5O6-δ, SFM). The resulting F-doped SFM cathode (Sr2Fe1.5Mo0.5O6-x-δFx, SFMF, x = 0, 0.1, 0.2 and 0.3) exhibits improved crystal structure symmetry and enhanced electrocatalytic activity for the ORR. At 800 °C, the polarization resistance of F-doped SFM is significantly decreased to 0.072 Ω cm2, which can be ascribed to the enhanced oxygen reduction capacity. Moreover, F-doping reduces the metal-oxygen bond energy and accelerates the transportation of O-ions during the electrochemical process, resulting in significantly enhanced ORR activity.