Abstract
Solid oxide fuel cells (SOFCs) are efficient electrochemical devices, converting chemical
energy into electricity. However, the main drawback for the wide commercial use of SOFC
is its high operational temperature (around 750 ℃). Therefore, this research project mostly
focuses on developing new nanostructured electrode composites and low-temperature
fabrication techniques to further improve the performance of SOFCs at lower operating
temperatures. The first approach to reach lower operating temperatures for SOFCs was to
develop a novel, low-cost, efficient and environmentally friendly synthesis method to
improve the microstructural properties of both the electrolyte and anode materials. In this
regard, gadolinium doped ceria (GDC) nanocrystalline powders were synthesized through
a modified coprecipitation method using, for the first time, ammonium tartrate as an
environmentally friendly, inexpensive, and novel precursor. The developed synthesis
method 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 synergetic
effect was found among different constituents of the anode composites, where the strong
interaction between the well dispersed metal oxide nanocrystalline particles and the GDC
crystallite phase showed to shift the reduction temperature of the anode composites to lower
temperatures than those of bare anode constituents. Considering targeted objectives of
developing low temperature SOFCs (LT-SOCs), having a broad choice of material and
using metallic parts, avoiding high temperature fabrication processes was of great
importance in this project. With regards to the fabrication of anode supported SOFCs, all
synthesised anode and electrolyte powders illustrated a high sinteractivity, promoting the
densification of the GDC electrolyte film during the co-sintering process at considerably
low sintering temperatures (1100 ℃). The fabricated cells were evaluated using different
advanced electrochemical techniques, such as electrochemical impedance spectroscopy
(EIS), to evaluate mechanisms during different operating modes. Finally, the
electrochemical performance of the fabricated cells was studied under fuel cell operating
conditions.