Abstract
The influence of rare earth ions on layered perovskite (AA'B2O5+δ) is the key to the development of highly active layered perovskite cathode. Herein, we make a systematic explanation through experiment and first-principles calculation. The lattice constant decreases with the decrease of Ln3+ ionic radius, resulting in a smaller space of interstitial oxygen position and increasing oxygen Frenkel energy. The electrochemical activity of LnBaCo2O5+δ (Ln = Pr, Nd and Sm) electrodes decreases with the decrease of Ln3+ ionic radius, which is mainly attributed to a lower oxygen Frenkel energy. Electrochemical impedance spectra tests show that there are significant differences in the surface exchange process of oxygen because of different surface oxygen vacancy concentration for LnBaCo2O5+δ. For Ln = Pr, Nd, and Sm cathodes, the maximum power densities of the anode-supported Ni-YSZ/YSZ/GDC/LnBaCo2O5+δ single cells reach 1.48, 1.36 and 1.06 W/cm2 at 800 °C, respectively, indicating that PrBaCo2O5+δ with the maximum rare earth ion radius exhibits better oxygen reduction reaction. These findings provide guidance for the design and fabrication of highly active layered perovskite electrode materials.
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