Cathodes based on (La, Sr)MnO3 modified with PrO2 − x

Abstract

The electrochemical characteristics of composite cathodes made of (La, Sr) MnO3-(Zr, Sc)O2 (LSM-SSZ), modified with PrO2 − x additive, and designed for application in solid oxide fuel cells at moderately high temperatures were studied. The relationship between activity of catalytically modified composite LSM-SSZ cathodes and dispersity of electrocatalyst was revealed. The boundaries of the temperature range with the maximum dispersity of electrocatalyst and electrochemical activity of cathodes were found. The composite LSM-SSZ cathodes modified with PrO2 − x were shown inert with respect to oxidation reactions of hydrocarbon fuel (methane) and highly active electrochemically with respect to oxygen reaction in non-equilibrium gas mixture of CH4 and O2. In cells with (Ce, Sm)O2 (SDC) and (Zr, Y)O2 (YSZ) electrolytes, their overvoltage is below 80 mV at the current density about 0.5 A/cm2 and temperature of 600°C. These electrodes can be used as cathodes in single-chamber fuel cells. Long-term experiments were carried out to study time stability of characteristics of the said composite cathodes. The studied electrodes show parabolic or damped exponential time curves of polarization resistance if contacting with YSZ or SDC electrolyte, respectively. According to the forecast based on the experimental regularities, the polarization resistance of LSM-SSZ cathodes in 10,000 h will not exceed 0.4 or 0.13 Ohm cm2, respectively, if YSZ or SDC electrolyte is used.