Electrolyte and Cathode Studies for Micro-Solid Oxide Fuel Cell
- PDF / 865,954 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 11 Downloads / 414 Views
1256-N16-50
Electrolyte and Cathode Studies for Micro-Solid Oxide Fuel Cell Yan Yan, Janine Conde and Paul Muralt Ecole Polytechnique Fédérale de Lausanne EPFL, Laboratoire de Céramique, Station 12, 1015 Lausanne, Switzerland
ABSTRACT Sputter deposited YSZ thin films were studied for the application as electrolyte membrane in micro solid oxide fuel cells. A new micro-machined test structure was developed to test 200 µm fuel cell membranes that are integrated onto silicon substrates. The membranes are liberated by means of deep silicon dry etching from the backside, and both contacts are situated on the front side of the wafer. Annular Pt electrodes provide contacts to specific anode and cathode layers. Preliminary tests are reported for the situation without specific electrodes. At 450 °C, an OCV of 570 mV, and a maximal power of about 0.55 mW/cm2 is obtained. LaSrMnO electrodes deposited by pulsed laser deposition were evaluated by electrical impedance spectroscopy. The dense films yielded too high ASR values. Interestingly, these could be reduced by applying a DC bias voltage. INTRODUCTION Low temperature SOFCs, operating under 600oC, are considered to be an effective approach to supply power in small systems requiring a few tens of Watts only [1], for example digital cameras. At such low temperature, ion transport losses in the electrolyte is a key limiter. It is necessary to either change to higher conductivity materials, or to reduce the thickness. The latter is much more convenient. Yttria-stabilized zirconia (YSZ) membranes of micrometer or sub-micrometer thickness meet most of the requirements [2-6]. However, mechanical integrity under fuel-cell operating conditions becomes an issue [6]. YSZ nanolaminates were realized by different deposition methods: reactive sputtering [7], pulsed laser deposition [8], spray pyrolysis [2] and atomic layer deposition [4]. Double layers of YSZ/Gd0.2Ce0.8O1.9 were investigated as well as multilayers of different microstructures of YSZ [7]. The performances of micro fuel cell devices are also limited by the diffusion and gas exchange kinetics of electrode materials. Since Pt electrodes are dewetting quickly at operating temperature, mixed ionic/electronic conducting perovskites such as La1-xSrxCo1-yFey O3-δ, or strontium-substituted lanthanum manganese (LSM) have gained substantial attention. In this paper, we report on the fabrication and characterization of newly designed micro SOFC silicon chips of 64 free-standing electrolyte membranes for testing electrolyte and electrode materials. The idea is to have both electrode contacts on the same chip side in order to measure cells with electrical probes on a hot chuck, and to use deep silicon dry etching for the liberation of membranes. In the present contribution we report on Pt/YSZ/CGO/Pt structures evaluated with the new micro devices. The conductivity through the electrolyte films was evaluated by variable temperature impedance spectroscopy. LSM electrodes and Pt/LSM electrodes were evaluated by the same method.
EXPERIMEN
Data Loading...
