使用陽極氧化鋁模板製造鎳奈米線於提升電解水效率之應用

Abstract

電解水是最簡單製造氫氣與氧氣的方式，在電解水過程減少能源的消耗是一個重要的議題，而增加反應電極的表面積使電解水時的操作電壓降低是其中一種方法。我們利用氧化鋁模板(AAO)製造鎳奈米線，並利用它高深寬比的特性增加在電解水反應的有效表面積。利用直流脈衝電鍍的方式將鎳金屬沉積至AAO的孔洞當中，再使用KOH溶液將AAO模板移除留下高深寬比的鎳奈米線。在我們的研究當中製造出直徑250 nm、長度20~60 μm的鎳奈米線。將鎳奈米線組成的電極使用在電解水反應當中，使用中性及鹼性兩種電解液產生氧氣。在0.25 M的硫酸納當中，使用製造出來的鎳奈米線電極作為陽極可以在1.2 V的電壓下產生20 mA/cm2的電流密度，而以商用鎳片作為陽極則需1.7 V才能產生20 mA/cm2的電流密度。在1 M的KOH溶液當中外加1.8 V電壓，鎳片作為陽極可以產生63 mA/cm2的電流密度。而使用鎳奈米線電極則能產生308 mA/cm2。在產生氫氣的反應中，使用鹼性的KOH作為電解液。在外加電壓為-2 V時，電流密度也從使用鎳片產生的-104 mA/cm2提高到使用鎳奈米線電極時的-388 mA/cm2。實驗的結果也證實鎳奈米線組成的電極可以持續工作超過24小時。

Oxygen and hydrogen both play important roles because they are the feedstocks for fuel cells. Among many production methods, the water electrolysis is the simplest one. To reduce energy consumption, the operating cell voltage should be reduced as much as possible at practical current densities. Our efforts in this area are mainly focused on the development of nickel-based electrodes because of their acceptable catalytic capabilities at reasonable material cost. We used the direct-current (DC) pulse electrodeposition to fabricate nickel nanowires with in the AAO pore channels. After removing the AAO template by KOH solution, we obtained much larger surface areas. We fabricate nickel nanowires with lengths of 20 to 60 μm and 250 nm in diameter by adjusting the current densities in the DC pulse electrodeposition. We used these nickel nanowires electrodes to produce oxygen in neutral and alkaline solutions, and to generate hydrogen in alkaline electrolyte. The performances for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) by using the nickel nanowires electrodes were significantly improved than that of nickel plate. Otherwise, the nickel nanowires electrodes can work continuously over one day.