(Invited) Boosting Solid Oxide Fuel Cell Performance through the Effect of of Interstitial Oxide Ion Supplying of Oxygen Storage Capacitance Materials at Cathodic Functional Layer

Abstract

Chemical compatibility between the hierachical interface components in solid oxide fuel cells (SOFCs) is an emerging critical issues that significantly impact the durability of SOFCs. However, there are several challenging issues to be solved: cost-effective manufacturing configuration, lowering the operating temperature, and durability. The creation of novel materials or long-lasting electrode/electrolyte interfaces that permit high activity (oxygen reduction or fuel oxidation) while maintaining long-term stability is one of the major barriers to the commercialization of the SOFC Rare-earth doped ceria (REDC) is commonly used to enhance durability and activity in solid oxide cells (SOCs) engineering, with Gd-doped ceria (GDC) being a popular choice for interlayer and additives in solid oxide fuel cells (SOFCs). However, the Ce diffusion into the lattice of ZrO2of YSZ-based electrolyte as a solid solution at high-temperature manufacturing still is remained to be solved. In this study, we conducted La-doped CeO2 (LDC), whose Ce-sites are highly occupied with La to avoid a solid solution of Ce-Zr, as a functionalized interlayer between YSZ-based electrolyte and cathode. When LDC (La-doped CeO2, LDC, Ce0.6La0.4O2−δ) or Bi doped Cerium Oxide buffer layer was optimized at lowering sintering temperature to prevent a La2Zr2O7 impurity reaction, the improved electrochemical performance was achieved at the maximum power density (MPD) of ~1.43 W cm-2 at 800 oC. The high substitution of La3+ into the ceria lattice improves the oxygen non-stoichiometry of LDC, leading to improve the oxide ion supplying of the cathode side during the high current operation. Consequently, we firstly propose that the larger oxygen storage or supplying capacitance (OSC) effect of the interdiffusion layer composition (La, Zr, Ce, Y)O2 in La-doped CeO2 (LDC) is responsible for the positive enhancement of the oxygen reduction reaction (ORR) at high current ranges through interstitial oxygen supply at the cathode/electrolyte interface rather than (Gd, Zr, Ce, Y)O2 in GDC. The OSC of the LDC is higher than that of the GDC, and it effectively enhances the electrochemical performance of the cathode interface in the SOFCs because it may be affected by the high oxygen carrier concentration of the LDC, the higher oxygen releasing, and storage capacitance. This revealed that the effect of oxygen releasing, and storage capacity of the buffer layer might be the cause of improved performance. Consequently, the cell containing the high OSC buffer layer fabricated at 1250 oC to avoid interfacial insulating layers, such as La2Zr2O7 impurities, successfully displayed a dramatically high-power density value. Figure 1