Composite materials of Ti-doped strontium ferrite and ceramic electrolytes as both the anode and cathode in symmetrical solid oxide fuel cells

Compared to traditional solid oxide fuel cells (SOFCs), symmetrical solid oxide fuel cells (SSOFCs) have attracted great attention because of several advantages as follows; the mechanical and chemical compatibility between the... [ view full abstract ]

Compared to traditional solid oxide fuel cells (SOFCs), symmetrical solid oxide fuel cells (SSOFCs) have attracted great attention because of several advantages as follows; the mechanical and chemical compatibility between the electrolyte and electrodes by reducing the number of different cell components and interfaces and much easier production of SSOFC because of assembly of the electrolyte and electrodes from just one thermal process, reducing fabrication time and costs. Among the redox stable electrode candidates, high valence metal ion-doped strontium ferrites, M-doped SFOs (M= Ti⁴⁺, Si⁴⁺, Zr⁴⁺, Mo⁶⁺ and W⁶⁺), were reported to possess high redox stability in a wide range of temperatures and oxygen partial pressures. In particular, Ti-doped SFO is one of the most promising materials due to its relatively low polarization resistance and chemical compatibility with different electrolytes (i.e., GDC, LSGM). In this regard, we used composite electrodes of Ti-doped SFO and different electrolytes (i.e., YSZ, GDC, LSGM, and LSGMZ) for both cathode and anode in SSOFCs in order to improve electrochemical performances. First, Sr_0.8Fe_1-xTi_xO_3-δ (x=0.2) was prepared by solid state reaction. The doping of Ti in SFO was confirmed by various tools such as powder X-ray diffraction, energy dispersive spectroscopy, x-ray absorption spectroscopy and so on. The composite materials of SFTO and different electrolytes were prepared by mechanical mixing using a ball miller and subsequent heat treatment. Among electrolytes used, it was confirmed that YSZ is not suitable for use as an electrode material because of an occurrence of secondary phases, evidenced by PXRD. Among the others, the composite composed of SFTO and LSGMZ exhibited the highest efficiency operating as both cathode and anode with polarization resistance values of 0.3 Ω/cm² in cell condition test at 750 ^oC. The SSFC consisting of LSGMZ electrolyte and symmetric SFTO/LSGMZ composite electrodes showed a maximum power density of 500 mW/cm² at 750 ^oC. In this presentation, we will discuss our recent efforts in using the composite electrodes in SSFC, which include a synthesis procedure of materials, structural redox stability, and electrochemical performance.