Composite electrodes of Ti-doped SrFeO3-δ and LSGMZ electrolytes as both the anode and cathode in symmetric solid oxide fuel cells

Abstract

In this work, we attempt to find a suitable mixed composite electrode between perovskite Ti-doped strontium ferrite, SrFe1-xTixO3-δ (x = 0.2, SFTO) and different electrolytes, such as YSZ, GDC, LSGM, and LSGMZ, for use as both electrodes in symmetric solid oxide fuel cells (SSOFCs). The SFTO are first prepared by a sol-gel method and solid-state reaction. The substitution of Fe with Ti4+ in the SFO was confirmed by various analyses, such as powder X-ray diffraction, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. The electrolytes suitable for use in this system are selected by investigating the chemical compatibility between the SFTO and electrolytes through heat treatment and ionic conductivity measurements of the electrolytes as a function of temperature. According to the powder X-ray patterns, there is no chemical reactivity between SFTO and the electrolytes of GDC, LSGM, and LSGMZ. In contrast, YSZ is not suitable for use as a composite material because of the occurrence of secondary phases. The ionic conductivity test shows that the LSGMZ electrolyte is the best electrolyte at operating temperatures above 700 °C. The mixing ratios of SFTO and LSGMZ electrolytes are varied to determine the optimum performance of the SSOFCs. Compared to the electrode based on SFTO only, the SSOFC consisting of the LSGMZ electrolyte and symmetric SFTO/LSGMZ composite (2:1 wt% ratio) electrodes exhibits a lower electrode polarization resistance value with a higher performance consisting of a maximum power density of 700 mW/cm2 at an operating temperature of 800 °C in a button cell test.