Adjusting surface oxygen vacancies prompted perovskite as high performance cathode for solid oxide fuel cell

Highlights: • We firstly design a simple solution reduction method to modify the surface defect on cathode materials of solid oxide fuel cell. • The first principle predicted that the Vo-BCNS-10 would show a higher ORR compared with other samples. • The surface defect modification is beneficial to oxygen desorption which evidenced by EPR and O₂-TPD. • The ASR of Vo-BCNS-10 is 0.0059 Ω cm² at 800 °C with a maximum power density of 1372 mW cm⁻². • The charge transfer process determines the rate-determining-step of Vo-BCNS-10 cathode. -- Abstract: The oxygen reduction reaction (ORR) activity would significantly decrease when the operating temperature declines. Researchers usually use doping method to obtain defects in body phase, and then improve the activity of ORR. However, Surface defects play a more important role in ORR compared with body defects. Surface oxygen vacancies and band structure are closely related to oxygen reduction reaction, especially at low temperature. Therefore, we firstly design a simple solution reduction method to modify the surface defects on perovskite-type cathode materials and further investigate the relationship between oxygen vacancy concentration and electrochemical performance. The surface oxygen vacancies could improve the ability of oxygen absorption and desorption, thereby improving the activity of ORR. The result of theoretical calculation show that the oxygen vacancy concentration could change O p-band centre. Among all samples, the Vo-BCNS-10 (BaCo_0.8Nb_0.1Sc_0.1O_3-δ after 10 min reduction treatment) exhibits the lowest polarization impedance and the highest electrochemical performance. The area specific resistance is 0.0231 Ω cm² at 700 °C and the activation energy is only 114.16 kJ mol⁻¹. Experiments and theoretical calculation together reveal that a proper oxygen vacancy concentration is beneficial to obtain massive active site and adjust O p-band centre, thus significantly improving the ORR activity of material.