On the Fabrication of Three-Dimensional Nickel-Zinc alloys by electroplating and Their Performance of Hydrogen evolution in Alkaline Water Electrolysis;On the Fabrication of Three-Dimensional Nickel-Zinc alloys by electroplating and Their Performance of Hydrogen evolution in Alkaline Water Electrolysis

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题名:	On the Fabrication of Three-Dimensional Nickel-Zinc alloys by electroplating and Their Performance of Hydrogen evolution in Alkaline Water Electrolysis;On the Fabrication of Three-Dimensional Nickel-Zinc alloys by electroplating and Their Performance of Hydrogen evolution in Alkaline Water Electrolysis
作者:	拉維雅;Clemente, Lavinia Russell
贡献者:	應用材料科學國際研究生碩士學位學程
关键词:	Hydrogen evolution;electrodeposition;Nickel;Zinc;Raney Nickel
日期:	2020-04-08
上传时间:	2020-06-05 17:46:27 (UTC+8)
出版者:	國立中央大學
摘要:	本研究中使用微陽極引導析鍍(MAGE)來製造3維的鎳鋅合金。此製程以含0.5M鋅離子與0.25 M – 1.00 M鎳離子之氯化鹽為鍍浴，然而本製程與一般的傳統的平板電鍍不同。它屬於局部電化學析度(LECD)，是在不對稱性電場中以高電流密度進行。所製得之鎳鋅合金，其表面形貌由掃描式電子顯微鏡觀察；合金之化學組成，則使用能量色散X射線譜來分析；合金的結晶構造則由X光繞射分析，鑑定其結晶相組成。研究結果顯示: 當渡浴中鎳離子濃度增加，則製得合金微柱中的鎳含量也隨之增加；在鎳含量較高的微柱，其柱直徑較小，表面較粗糙。XRD分析顯示: 鎳鋅合金微柱主要由γ相的結構組成、至於鎳含量較低的合金中則含有純鋅相共存。為理解電鍍過程中的電場分布，此研究使用COMSOL Multiphysics 5.2商用軟體來模擬電場之強度與分佈。此外，動態陰極極化曲線研究則可提供鎳鋅合金的異常共鍍機制。已知鎳鋅合金在析氫反應中，過電位很低，並且具有極高的交換電流密度，因此廣用為鹼性電解水產氫的陰極催化劑材料。在本研究中以MAGE製造之鎳鋅合金，嘗試作為電解水產氫的應用研究，以循環伏安法和Tafel極化分析法來檢測在這些合金在鹼性水溶液中的產氫性能；同時使用掃描式電子顯微鏡、能量色散X射線譜、X光繞射分析來比對合金產氫前後的表面型態變化和晶體結構，以評估其產氫之壽命。結果顯示，鎳含量28 at.%的鎳鋅合金有最大的交換電流密度(1.94 mA/cm2)。由於其成分的合金對於HER電催化反應擁有高穩定性，因此可作為最具潛力的鹼性水電解之產氫材料。從循環伏安法中顯示:含有28 at.% 鎳的鎳鋅合金在鹼性水溶液中縱使進行了1000次循環，其反應活性也沒有絲毫降低。 ;A process named micro-anode guided electrodeposition (MAGE) was adopted to fabricate three-dimensional (3-D) nickel-zinc alloys in this work. This process was performed in the chloride baths containing 0.50 M [Zn2+] and [Ni2+] ranging in 0.25 M – 1.00 M. It belongs to one of localized electrochemical deposition (LECD) carried out under high current density in an asymmetric electrical field compared to the traditional planar electrochemical plating. The surface morphology, chemical composition, and the crystallographic phase composition of the 3D Ni-Zn alloys was examined using SEM, EDS and XRD respectively. It was found that the alloys containing higher nickel content reveal a rougher surface with a smaller diameter. With increasing the [Ni2+] concentration in the electrolyte, the Ni-content in the alloys increases. Analysis by XRD indicated that the Ni-Zn alloys are major consisting of γ-phase and some of them display a co-existence of pure Zn-phase from the baths with diluted [Ni2+] concentration. One commercial software (i.e., COMSOL Multiphysics 5.2) was used to simulate the strength and distribution of the electric field in the MAGE process. This simulation provided a quantitatively asymmetric distribution of the electric field. In addition, the study of cathodic polarization provided useful information to realize the mechanism of Ni-Zn electrodeposition, which is classified as the anomalous electroplating. Nickel-zinc alloys are well known catalyst to produce hydrogen gas in the alkaline water electrolysis because of high exchange current density and low over-potential of the hydrogen evolution reaction (HER). Techniques of cyclic voltammetry and Tafel polarization were conducted in the alkaline solution to study the availability of the Ni-Zn alloys to produce hydrogen gas. Prior to and post water electrolysis, the Ni-Zn alloys were examined using SEM, EDS and XRD to investigate the change their surface morphology, crystalline structure for estimation of their life. The alloy containing 28 at.% Ni was found to depict the highest exchange current density (i.e., at 1.94 mA/cm2) among the Ni-Zn alloys. This alloy 28 at.% Ni is considered as a very good candidate of cathode material in the alkaline water electrolysis due to the extreme stability of the electrochemical catalytic reactivity to the HER. Resultant from CV study of the Ni-Zn alloys with 28 at.% Ni, the reactivity remains no loss even it have withstood 1000 cycles in the alkaline water.
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