電解水產氫中極化作用之分析與研究; The investigation of polarization in water electrolysis

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Title:	電解水產氫中極化作用之分析與研究;The investigation of polarization in water electrolysis
Authors:	黃心華;Huang,Hsin-Hua
Contributors:	能源工程研究所
Keywords:	極化現象;水電解;等效電路;電化學阻抗頻譜;polarization, electrochemical impedance spectroscopy, water electrolysis
Date:	2013-07-25
Issue Date:	2013-08-22 12:03:14 (UTC+8)
Publisher:	國立中央大學
Abstract:	在水電解過程中，會有極化現象產生，極化現象又分為，濃度極化、活性極化以及歐姆極化，而極化現象是造成電解效率下降的原因之一。故本論文主要是藉由水電解的奈示圖(Nyquist)，來解釋其等效電路、極化現象、以及電極片上所生成的氧化現象…等。本文實驗所設定之參數為電解液氫氧化鉀濃度(10%、20%、30%、40%)，電解電位(2V、2.25V、2.5V、2.75V、3V)，電極間距(2mm、5mm、10mm)，電極為鎳電極，並用恆電位儀紀錄實驗所產生的數據，以探討反應在不同的狀況下，所產生的奈示圖。結果顯示，在不同電壓下，阻抗隨著電壓的增加而降低。而當濃度在30%時，會有最好的電解效益；濃度在過低或是過高的情況下，主要影響的是濃度極化，而濃度在20%以及30%時，主要影響落在活性極化上。通常活性極化在低電流時為主要的過電壓來源，濃度極化並不明顯；當電流升高至極限電流時，濃度極化急速上升，成為過電壓的主要來源。隨著電壓達到2.5V以上時，陰極表面開始有氧化現象產生，。而電極距離在2mm時，會有最佳的極化表現。 There is polarization phenomenon in water electrolysis. The polarization could be separatedinto three parts, namelyconcentration, active, and ohmic polarizations.The potassium hydroxide electrolyte concentration is set up from 10% to 40%, and the potential is set up from 2V to 3V. Electrode distance is kept at 2mm, 5mm, and 10mm, while the electrode materialis nickel. Then the potentiostat is used to record the data. Results show that the impedance decreases when theelectricpotential is increased. The optimal result occurs when the electrolyte concentration is 30%. If the concentration is too high or too low, concentration polarization is the main factor. When the concentration is at20% or 30%, active polarization becomes the primary factor.The overpotentialis usually due to the active polarization on low current, and the concentration polarization is not obvious at this time. When the current reaches the limit current, the concentration polarization becomes the main cause for the overpotential. When applied potential is over 2.5V, there will beoxided layers deposited on the cathode side surface. The best performanceoccurs as the electrode distance is 2mm. Key word: polarization, water electrolysis, equivalent circuit model, electrochemical impedance spectroscopy.
Appears in Collections:	[Energy of Mechatronics] Electronic Thesis & Dissertation

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