Fuel cells (FCs) convert the chemical energy of fuel directly to electricity. FCs are potential canditates for clean electricity sources in the future, provided that the main challenges halting their commercialization can be solved. Several different FC subtypes exist. This Thesis is focused on ceramic nanocomposite FCs (CNFCs) and single-layer FCs (SLFCs). Both of these FCs operate at intermediate temperatures, at around 500-600 °C. CNFC utilizes the traditional three-layer structure: anode, electrolyte, and cathode. The key component is the electrolyte, that consists of a composite of a solid oxide and a salt, here doped ceria and alkali carbonate mixture respectively. This composite electrolyte allows an efficient multi-ion conduction, reducing the ohmic losses in the cell. Excellent power densities, exceeding 1 W per square centimeter, were achieved with two different CNFCs in this Thesis. SLFC is a ground-breaking innovation where all FC functions are compressed into one single layer, consisting of a mixture of a semiconductor (here lithium nicke zinc oxide or copper iron oxide) and an ionic conductor (here doped ceria or doped ceria – alkali carbonate mixture). The SLFC desing allows to elimintate the challenges originating from the three-layer structure and to simplify the manufacturing procedure. In this Thesis, the working principle and performance-affecting factors of SLFCs were studied. The key findings include that the proton is dominating over the oxygen-ion in ionic conduction with the studied SLFC configuration and that applying the composite ionic conductor of CNFC to SLFC improves vastly the cell performance. Since both CNFCs and SLFCs are complex nanoscale structures, studying the microstructure of these devices with electron microscopy and X-ray spectroscopy are identified as crucial procedures to understand the macroscopic output. Systematic studies combined with modern microscopic methods are suggested as a pathway to push both SLFCs and CNFCs towards commercialization.
|Publication status||Published - 2020|
|MoE publication type||G5 Doctoral dissertation (article)|
- single-layer fuel cell
- ceramic nanocomposite fuel cell
- microscopic characterization