台灣四面環海，對於海水資源的取得唾手可得，並且台灣地理位處亞熱帶地區，具有較長的日照時間擁有豐富的太陽能源，因此我們未來的願景是利用太陽能來提供偏壓做為光電化學產生氫氣的動力，並且使用海水做為電解液，產生的氫氣能夠導入動力系統燃燒，燃燒過後的氫氣只會產生水而不像石化燃料會有溫室氣體的生成，產生的水又能夠導入電解水的系統循環再利用，然而在本篇論文中所使用的基板是n型氮化鎵，隨著電化學產氫的進行，會造成n型氮化鎵的光腐蝕並產生缺陷使光電流降低並抑制產氫效率，所以在本篇論文中著重於使用濺鍍(Sputter)的方式讓均勻、緻密的氧化鎳完整的覆蓋在n型氮化鎵之上，避免氮化鎵基板的光腐蝕影響產氫效率，以及能夠讓n型氮化鎵的工作壽命延長。
使用濺鍍之氧化鎳當保護層的原因在於，就光學特性而言並不會與氮化鎵的吸收波段重疊也不會吸收可見光，因此不會影響氮化鎵基板的吸光能力；就能帶的角度來說，氧化鎳與n型氮化鎵接合後形成p-n junction後，氮化鎵與氧化鎳接面的能帶彎曲有利於電洞傳輸到氧化鎳而不會累積在氮化鎵表面造成光腐蝕；最後從化學角度來分析，透過添加氧化鎳發揮催化劑的效果，達到降低氧化水產生氧氣的過電位，有利於從載子轉移到電解液產氧氣的能力，避免電洞累積在氮化鎵表面造成光腐蝕。
在本論文的第四章著重於探討不同厚度的氧化鎳對於光電化學系統產氫的影響，並透過穿透、反射圖譜等光學特性來觀察濺鍍上不同厚度的氧化鎳之後的發現經過電化學處後的氧化鎳薄膜由於會有表面粗化的效果因此n型氮化鎵基板能夠吸收較多的光，並且發現較厚的氧化鎳會造成遮光的效應，接著從XPS去分析表面的化學組成發現使用Sputter得到的氧化鎳同時具有Ni2+以及Ni3+，最後進行三電極電化學系統的量測，發現較薄的氧化鎳由EIS能夠看到阻值會降低，LSV中可以看到飽和電流會有上升的情形，以及經過穩定性測試以及收集的產物中都能夠看到濺鍍上4nm的氧化鎳能夠提升產氫效率以及能夠具有穩定的光電流。
在本論文中的第五章節中使用不同濃度的氫氧化鉀容易對於4nm氧化鎳進行電化學處理，並證明NiOOH的存在有利於使光生電洞與電解液反應達到抗腐蝕的目的，從XPS觀察氧化鎳經過不同濃度的氧化鎳處理後，使用0.2M KOH處理後的氧化鎳能夠完全轉換Ni2+變成Ni3+也就是轉變為NiOOH，並且從SEM圖能夠觀察到高濃度的氫氧化鉀造成氮化鎵的嚴重腐蝕產生較多的缺陷，導致產氫效率的低落，最後從電化學的量測中能夠看到使用0.2M KOH處理之後的氧化鎳由於存在比例較高的NiOOH能夠有效將光生電洞傳往電解液並氧化水生成氧氣達到抗腐蝕的效果，因此可以得到較高的光電流，從產物的收集也能夠得到較高的產氫效率。

Photoelectrochemical(PEC) devices that use n-type gallium nitride(n-GaN) as working electrode will have the problem of photocorrosion.The photocorrosion of n-GaN lead to the decrease of hydrogen production efficiency and shorten the working electrode life time. In order to improve hydrogen production efficiency long-term stability,we sputtered nickel oxide on n-GaN.Sputtered nickel oxide film has the property of transparent, chemically stable, electrocatalysts can provide a dense protective layer avoiding the photocorrosion of n-GaN.Futhermore, nickel oxide is a oxygen evolution catalyst can reduce OER overpotential,and it is facile to the oxidation of water to O2.
First, comparing the effect of sputtering 4nm and 40nm nickel oxide on n-GaN and apply to PEC system generate hydrogen.Finding that 4nm nickel oxide has higher saturation current in LSV measurement. It show that 4nm can address the problem of photocorrosion of n-GaN by playing the role of p-n junction will facilitate the separation of carriers and hole can transfer into electrolyte.We speculate that this is because Ni(OH)2 doesn’t completely convert into NiOOH.
In order to verify the existence of NiOOH is beneficial for reducing OER overpotential.Hence, electrochemical treatment of nickel oxide by using different concentrations of KOH,can convert Ni2+ into Ni3+.From XPS analysis, we can know that in the alkaline solution do electrochemical treatment can convert Ni2+ into Ni3+.

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