鎳鉬鎢合金微柱之MAGE製備及其在1M KOH中之產氫功能研究

Ni-Mo-W alloy Micro columns Prepared by MAGE and their Evolution of Hydrogen in 1M KOH

本研究是以微陽極導引電鍍法（Micro-anode guided electroplating, MAGE）製備鎳鉬鎢三元合金微柱，並探討其在1.0M KOH中之產氫電化學性質。微柱的優點是在極小的面積上製造出三維的電極取代薄膜電極，增加產氫催化電極的活性表面積；另一方面，則藉由鎳與鉬、鎢等過渡元素的協同效應，來製作具有優越產氫活性之三元合金微柱。本MAGE電鍍係以玻璃管披護直徑127μm之白金絲，露出其底面0.1267 mm2為陽極，而以直徑0.643 mm之漆包銅線露出其橫截面0.325 mm2為陰極。兩極間偏壓設在6.5 V，間距則設定在20、40、60、80和100μm等五個條件進行電鍍。電解液配方係由0.38 M氯化銨、0.36 M焦磷酸鈉、0.15 M六水硫酸鎳、0.064 M二水鉬酸鈉、0.04 M二水鎢酸鈉加水製成。電鍍分別經1472、1780、2514、3083、3227秒鍍出1 mm高度之微柱。所得微柱經SEM觀察其表面形貌、EDS分析化學成分、XRD測定晶體結構等。隨後，將合金微柱浸入1.0M KOH中進行循環伏安法、塔弗極化曲線測試，觀察鎳鉬鎢合金電化學性質與析氫之效能。

The nickel-molybdenum-tungsten ternary alloy microcolumns were prepared by a micro-anode guided electroplating (MAGE) method and their electrochemical characters to serve as a cathode of water electrolysis in 1.0M KOH for hydrogen production was explored. An advantage of the microcolumns is to construct3-dimensional array of electrodes on a tiny area to offer effectively catalytic hydrogen reduction as compared to a wide thin-film electrode. On the other hand, the synergistic effect among Ni, Mo and W benefits a superior reactivity in hydrogen reduction than the usual ternary Ni-alloys. In MAGE, a Pt-wire (in a diameter of 127 μm) mounted with glass capillary to expose a disc of the area at 0.1267 mm2was used as a micro anode; an enameled copper wire (0.643 mm in diameter) to expose one end in 0.325 mm2was the cathode. A bias of 6.5 V was set between the microanode and cathode and their separation was fixed at 20, 40, 60, 80 and 100 μm to perform the electroplating. The bath was formulated by 0.38 M ammonium chloride, 0.36 M sodium pyrophosphate, 0.15 M nickel sulfate hexahydrate, 0.064 M sodium molybdate dihydrate and 0.04 M sodium tungstate dihydrate. After 1472, 1780, 2514, 3083, and 3227 seconds of electroplating, microcolumns with a height of 1 mm are plated out. The surface morphology of microcolumns was examined through SEM, chemical composition was determined by means of EDS, and crystal structure analyzed with XRD. The effect of electric field on the morphology, chemical composition, crystal structure of the columns was of interest. Then, cyclic voltammetry (CV), Tafel polarization of the alloy microcolumns in 1.0M KOH were explored to estimate the availability of the microcolumns to act the cathode in the alkaline electrolysis of water in production of hydrogen gas.