固態氧化物燃料電池使用甲烷燃氣之性能和電化學阻抗實驗研究;An Experimental Study on Performance and Electrochemical Impedance of Solid Oxide Fuel Cells using Methane

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Title:	固態氧化物燃料電池使用甲烷燃氣之性能和電化學阻抗實驗研究;An Experimental Study on Performance and Electrochemical Impedance of Solid Oxide Fuel Cells using Methane
Authors:	詹彥信;Chan,Yen-Hsin
Contributors:	機械工程學系
Keywords:	固態氧化物燃料電池;鈕扣型陽極支撐全電池;直接甲烷燃氣;碳沉積;加濕效應;電化學阻抗頻譜;SOFC;anode-supported button full cell;direct methane operation;carbon deposition;humidification;electrochemical impedance spectra
Date:	2014-08-13
Issue Date:	2014-10-15 17:19:58 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文使用實驗室已建立之加壓型固態氧化物燃料電池(Solid Oxide Fuel Cell, SOFC)鈕扣型實驗載具，量測分析陽極端使用甲烷燃氣所產生之碳沉積效應，以及其對鈕扣型陽極支撐全電池性能曲線(I-V curve)與電化學阻抗頻譜(Electrochemical Impedance Spectra, EIS)之影響。實驗條件為固定氣體流率(陽極CH4 + N2: 50 + 150 = 200 sccm 和陰極Air: 200 sccm)，在溫度 750 oC 和壓力1 atm，分別使用加濕(約3% H2O)與未加濕陽極甲烷燃氣，並分別量測其I-V curve 與EIS，以探討加濕效應對碳沉積之影響。在固定負載條件下(0.8 V)，持續量測電池性能16 小時 (每隔2 小時量測一次，共9次含開始第一次量測)，以探討在固定負載條件下之電池操作時間對碳沉積對和電池性能的影響。在進行前述碳沉積實驗前，於陽極端先通入氫氣(H2： 200 sccm)，並量測其性能和EIS，以作為碳沉積實驗之基本比較數據。並且，在碳沉積實驗後，以氫氣還原法，通入氫氣取代陽極甲烷/氮燃氣，以探討碳沉積是否可以被還原？以及其對電池性能有何影響？最後，使用掃描式電子顯微鏡－微區元素分析儀(Scanning Electron Microscope － EnergyDispersive Spectrometry, SEM-EDX)，來分析驗證使用甲烷燃氣的電池碳沉積現象。實驗結果顯示可知，使用加濕甲烷燃氣能明顯降低EIS 之極化阻抗，並且有效地提高電池性能。例如：在750 oC 和0.7 V 條件下，使用未加濕甲烷燃氣的功率密度為130 mW/cm2，而使用加濕甲烷燃氣的功率密度 ii則可被提升至256 mW/cm2。由SEM-EDX 針對陽極支撐全電池片所拍攝之微觀照片，確認使用甲烷燃氣的電池片有碳沉積現象之存在。本研究結果，應有助於進一步地了解SOFC 使用天然氣(甲烷)為陽極燃氣，所形成碳沉積之現象，及其對SOFC 電化學反應機制之影響，這對未來SOFC 產業之建立和推廣應有所助益。;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.
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