以微電鍍法析鍍鎳鎢合金微結構並研究其在鹼性溶液電解產氫行為;Ni-(20~40 at. %) W alloyed micro features prepared by MAGE process and their electrolytic behavior of hydrogen production in the alkaline solution

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Title:	以微電鍍法析鍍鎳鎢合金微結構並研究其在鹼性溶液電解產氫行為;Ni-(20~40 at. %) W alloyed micro features prepared by MAGE process and their electrolytic behavior of hydrogen production in the alkaline solution
Authors:	李盈家;Lee-Ying-Chia
Contributors:	材料科學與工程研究所
Keywords:	微電鍍;鎳鎢合金;產氫
Date:	2020-08-20
Issue Date:	2020-09-02 15:45:00 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究中使用微陽極導引電鍍(Microanode-guided electroplating, MAGE)來製造鎳鎢合金微結構。電鍍製程中改變鍍浴酸鹼值(6.0~7.5)與溫度(60 °C~75 °C)等條件對析鍍鎳鎢合金微結構表面形貌、化學組成、結晶構造、機械性質等之影響。表面形貌以冷場發射掃描式電子顯微鏡觀測，晶體構造以X光繞射儀分析。電鍍過程監測析鍍電流，並對產物秤重，以計算電流效率。結果顯示: 鍍浴pH 在7.5、溫度75 °C時，所產出的鎳鎢合金微結構具較平滑表面，鎢含量可達37 at.%。若以鎳鎢合金作為鹼性溶液電解產氫的陰極時，由於其氫還原的交換電流密度高、氫過壓低，因而成為當前產氫的熱門陰極材料。本論文以MAGE所製造出來的鎳鎢合金微結構，以循環伏安法、計時電位法、Tafel極化分析法來檢測此合金在鹼性水溶液中的產氫表現。結果顯示:含37 at.% W的鎳鎢合金微結構，具有最大的交換電流密度(6.01  10-1 mA/cm2)，最小的Tafel slope (80 mV/dec)。計時電位法之結果顯示，含38 at.% W的合金微柱在1.0 M KOH溶液中，以定電流-300mA/cm2經過六小時的電解產氫，其電位始終維持在-0.30±0.07 V，並無明顯的漂移，顯示此材料相當穩定，是鹼性水溶液電解產氫及有潛力之候選材料。 ;Micro-anode guided electrodeposition (MAGE) process was used to fabricate three-dimensional (3-D) micro features of Ni-W alloys in this work. The effect of pH value (from 6.0 to 7.5) and the bath temperature (60~75 °C) on the surface morphology, chemical composition, crystallographic microstructure and mechanical property was investigated. The surface morphology was observed through SEM and the chemical composition determined by EDS; the crystallographic microstructure phase was examined by XRD. The micro feature was weighed and compared to the overall electrical quantity evaluated by integration of the current with time to calculate the cathodic current efficiency. As a result, the Ni-W micro features containing 37 at.% W in smooth surface was attained in a 75 °C-bath with pH of 7.5. Nickel-tungsten alloy is known as a good cathode material used to produce hydrogen gas by means of electrolysis in the alkaline water solution because of high exchange current density and low overvoltage of the hydrogen evolution reaction (HER). Micro features of the Ni-W alloys from MAGE were investigated in terms of cyclic voltammetry (CV), chronoamperometry (CP) and Tafel polarization to study their cathodic behavior of water electrolysis. The alloy containing 37 at.% W resulted from the MAGE in the 75 °C-bath with pH of 7.5 revealed the best HER efficiency. It demonstrated the highest exchange current density (6.01 x 10-1 mA/cm2) and lowest Tafel slope (80 mV/dec). The chronopotentiometry of the 37 at.% W alloy conducted at- 300 mA/cm2 in1.0 M KOH displayed a stable potential at -0.30±0.07 V without showing any significant shift within 6 hours. This fact indicates that this material is a stable and excellent cathode candidate for HER in the alkaline electrolysis.
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