| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 102 === A high-pressure solid oxide fuel cell (SOFC) experimental setup, which has been established in our laboratory, was used to measure and analyze the impact of carbon deposition on an anode-supported button full cell when using methane as a fuel in the anode based on power generating characteristics and electrochemical impedance spectra (EIS) measurements of the button full cell. All experiments were conducted at constant flow rates (CH4 + N2: 50 + 150 = 200 sccm in anode and air: 200 sccm in cathode) and at fixed
temperature (750 oC) and pressure (1 atm). Both humidified (about 3 % H2O added) and nonhumidified methane fuels were applied. By comparing their measured current-voltage curves
(I-V curve) and EIS data, the influence of adding a small amount of water to the carbon deposition of SOFC may be investigated. To further analyze the effect of operation time on the carbon deposition, measurements at a constant voltage (0.8 V) were continuously taken for 16 hours (every two hours one measurement, total 9 measurements including the first starting measurement). Before starting the carbon deposition experiment, we used hydrogen (H2: 200 sccm) in the anode to measure the button full cell’s I-V curves and EIS that served as a baseline data. After the completion of the carbon deposition measurements, hydrogen (H2: 200 sccm in anode) was again used to see whether the carbon deposition could be reduced and what happened to the cell performance. In the end of experiment, we applied the Scanning Electron Microscope－Energy Dispersive Spectrometry (SEM-EDX) to examine whether the carbon deposition did occur in the aforesaid anode-supported button full cell when methane was used. Results show that by adding a small amount of water into the fuel (humidified methane), the polarization resistance of EIS of the cell can be effectively decreased as compared to the case without humidification (non-humidified methane), resulting in a clear increase of the cell performance. For example, at 750 oC and 0.7 V, the power density for the case of humidified methane was 256 mW/cm2, while only 130 mW/cm2 for the case of non-humidified methane. Based on SEM-EDX micro-structure images, it is confirmed that the carbon deposition occurs in the present anode-supported button full cell. These results should be of help in understanding the carbon deposition phenomenon and its impact to the electrochemical mechanism of SOFC when using nature gas as the anode fuel. This may beuseful for the promotion of the application of SOFC.
|
|---|
