Roberto Neagu

Thin Film Solid Oxide Fuel Cells Deposited by Spray Pyrolysis

Two techniques of spray pyrolysis, namely, electrostatic and pneumatic spray deposition, were used to deposit samaria-doped ceria (SDC) electrolyte and lanthanum strontium cobalt ferrite (LSCF) cathode on cermet or metal supported anodes for solid oxide fuel cells (SOFCs) operated at reduced temperature. The deposition processes, the properties of the deposited films, and the electrochemical performances of the fabricated cells are reported in this paper. The deposited SDC electrolytes were dense and gas-tight, and had good adhesion to the underlying anodes. The deposited LSCF cathode had a preferred morphology to facilitate the transport of oxygen gas and effective contact with the electrolyte. Button cell testing indicated that the SOFCs with electrolyte or cathode deposited by spray pyrolysis had good electrochemical performance. This study demonstrated that spray pyrolysis is a cost-effective process for fabricating thin film SOFCs, especially metal supported SOFCs.

Spray Pyrolysis Deposition of Electrolyte and Anode for Metal-Supported Solid Oxide Fuel Cell

Metal-supported solid oxide fuel cells (SOFCs) offer many advantages, including increased robustness, improved thermal shock resistance, and decreased cost. However, fabricating metal-supported SOFCs using conventional techniques is both very difficult and very costly. In this study, two processes of spray pyrolysis deposition, pneumatic spray deposition and electrostatic spray deposition, were used to deposit samaria-doped ceria (SDC) electrolytes on different substrates and NiO-SDC anodes on porous stainless steel substrates. A cathode layer was subsequently applied on the electrolyte by stencil printing for electrochemical testing. The test results indicated that the electrolyte had reasonable cell performance, but the topography of the anode needed optimization. It was also discovered that the porous ferritic stainless steel 430 substrate used in this study did not have sufficient oxidation resistance as the substrate of a metal-supported SOFC.

Low Platinum Electrodes for Proton Exchange Fuel Cells Manufactured by Reactive Spray Deposition Technology

Reactive spray deposition technology (RSDT) is a method of depositing films or producing nanopowders through combustion of metal-organic compounds dissolved in a solvent. This technology produces powders of controllable size and quality by changing process parameters to control the stoichiometry of the final product. This results in a low-cost, continuous production method suitable for producing a wide range of fuel cell related catalyst films or powders. In this work, the system is modified for direct deposition of both unsupported and carbon supported layers on proton exchange membrane (PEM) fuel cells. The cell performance is investigated for platinum loadings of less than 0.15 mg/cm using a heterogeneous bi-layer consisting of a layer of unsupported platinum followed by a composite layer of Nafion®, carbon and platinum. Comparison to more traditional composite cathode architectures is made at loadings of 0.12 and 0.05 mgplatinum/cm. The composition and phase of the platinum catalyst is confirmed by XPS and XRD analysis while the particle size is analyzed by TEM microscopy. Cell voltages of 0.60 V at 1 A/cm using H2/O2 at a loading of 0.053 mgplatinum/cm have been achieved.

Nanostructured YSZ Thin Film for Application as Electrolyte in an Electrode Supported SOFC

The development of solid oxide fuel cell with thin film concepts for an electrode supported design based on the yttria-stabilized zirconia has demonstrated favourable results due to its high chemistry stability in oxidization and environment reduction. The spray pyrolysis process was investigated in order to obtain dense thin films of YSZ on different substrates. The precursor solution was obtained by zirconium and yttrium salt dissolutions in a mixture of water and glycerine in several ratios to study the solvent influence. The substrate was initially heated at 600 °C and during the deposition it ranged from 260-350°C, finishing at a fast increase in temperature of 600°C. The heat treatment was carried out in four different temperatures: 700 °C, 750 °C, 800 °C, and 900 °. The precursors were characterized by thermal analysis. The microstructures of the films were studied using scanning electron microscopy and X-ray diffraction. The results obtained showed that the films obtained were crystalline before the heat treatment process and have shown ionic conductivity above 800°C.