Probing oxygen vacancy effect on oxygen reduction reaction of the NdBaCo₂O_5+δ cathode for solid oxide fuel cells

In this work, abundant oxygen vacancies are introduced into NdBaCo₂O_5+δ (NBCO) by partial substitution of cobalt to facilitate the electrochemical activity of ORR. The oxygen vacancy concentration of NdBaCo_1.8Sc_0.2O_5+δ (NBCSc-2) is more than twice as that of NdBaCo₂O_5+δ. The increased oxygen surface exchange, bulk diffusion coefficients and adequate conductivity for NBCSc-2 can be responsible for the decrease of oxygen ion transfer activation energy. Consequently, the NBCSc-2 cathode shows a significantly reduced polarization impedance of 0.035 Ω cm² at 700 °C, which is only about 35% of NBCO. We also investigate the influence of the doping strategy on the stability of cathode. Thus, the enhanced ORR kinetics and high durability make NBCSc-2 as potential cathode material for solid oxide fuel cells.