Development of nano-composite materials for low-temperature solid oxide fuel cells (LT-SOFCs)

Abstract

Solid oxide fuel cells (SOFCs) are efficient electrochemical devices, converting chemicalenergy into electricity. However, the main drawback for the wide commercial use of SOFCis its high operational temperature (around 750 ℃). Therefore, this research project mostlyfocuses on developing new nanostructured electrode composites and low-temperaturefabrication techniques to further improve the performance of SOFCs at lower operatingtemperatures. The first approach to reach lower operating temperatures for SOFCs was todevelop a novel, low-cost, efficient and environmentally friendly synthesis method toimprove the microstructural properties of both the electrolyte and anode materials. In thisregard, gadolinium doped ceria (GDC) nanocrystalline powders were synthesized througha modified coprecipitation method using, for the first time, ammonium tartrate as anenvironmentally friendly, inexpensive, and novel precursor. The developed synthesismethod was successfully applied for the synthesis of a range of anode composites,including Ni-/GDC, Co/GDC, Co-Zn/GDC, Co/Cu-GDC, and Fe-Cu/GDC. A synergeticeffect was found among different constituents of the anode composites, where the stronginteraction between the well dispersed metal oxide nanocrystalline particles and the GDCcrystallite phase showed to shift the reduction temperature of the anode composites to lowertemperatures than those of bare anode constituents. Considering targeted objectives ofdeveloping low temperature SOFCs (LT-SOCs), having a broad choice of material andusing metallic parts, avoiding high temperature fabrication processes was of greatimportance in this project. With regards to the fabrication of anode supported SOFCs, allsynthesised anode and electrolyte powders illustrated a high sinteractivity, promoting thedensification of the GDC electrolyte film during the co-sintering process at considerablylow sintering temperatures (1100 ℃). The fabricated cells were evaluated using differentadvanced electrochemical techniques, such as electrochemical impedance spectroscopy(EIS), to evaluate mechanisms during different operating modes. Finally, theelectrochemical performance of the fabricated cells was studied under fuel cell operatingconditions