Abstract
Pr-deficient Pr1−xBaCo2O5+δ (P1−xBCO) oxides are evaluated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). Effects of Pr-deficiency on electrical conductivity, thermal expansion and electrochemical properties are investigated. Both the conductivity and thermal expansion coefficient (TEC) decrease with increasing Pr-deficiency. All of the conductivity, thermal expansion and TGA measurements demonstrate the existence of high temperature order-disorder transition. The oxygen reduction mechanism for P1−xBCO cathodes are characterized by electrochemical impedance spectroscopy. Over the temperature range of 600−800°C, the cathode polarization resistance is mainly contributed from electronic charge transfer over the cathode surface. Proper Pr-deficiency reduces cathode polarization resistance (Rp), and the lowest Rp (0.081Ω cm2 at 700°C) is obtained for the P0.92BCO cathode. In addition, the effects of order-disorder transition on the properties of P1−xBCO cathodes have also been discussed. Maximum power densities of a single-cell with P0.92BCO cathode on 300-μm thick Sm0.2Ce0.8O1.9 (SDC) electrolyte achieve 446–987mWcm−2 at 650–800°C. These results suggest that, among various P1−xBCO oxides, P0.92BCO is the most promising candidate cathode material for IT-SOFCs.
Published Version
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