Sintering Aids Strategies for Improving LSGM and LSF Materials for Symmetrical Solid Oxide Fuel Cell

R&D in the area of high-temperature symmetrical electrochemical devices is needed to meet the challenges of hydrogen energy. In the present study, the effect of Fe2O3 and CuO sintering aids on the electrochemical properties of the highly conductive solid electrolyte La0.8Sr0.2Ga0.8Mg0.2O3−δ and La0.6Sr0.4FeO3−δ electrodes for symmetrical solid oxide fuel cells was investigated. It is shown that the use of sintering aids leads to an improvement in grain boundary conductivity and allows us to reduce the sintering temperature to obtain a dense electrolyte with the same level of conductivity. It is shown for the first time that the nature of the sintering aids and the sintering temperature affect the La0.6Sr0.4FeO3−δ electrode activity differently depending on the gas environment (air or hydrogen). On the basis of the analysis of the impedance spectra by the distribution of relaxation times, assumptions were made about the nature of the rate-determining steps of hydrogen oxidation and oxygen reduction. It is shown that the nature of the rate-determining steps can change depending on the electrode sintering temperature. It was found that among the studied electrodes, La0.6Sr0.4FeO3−δ with 3 wt.% Fe2O3 sintered at 1050 °C is optimal in terms of activity in oxidizing and reducing atmospheres.