本實驗使用n型砷化鎵半導體，為一個小能隙的半導體，理論上能吸收大部分的太陽能能量，在透過施加偏壓調整能帶相對於水氧化電位的位置後，能有效的將太陽能轉換至化學能。但以n型砷化鎵為光電陽極下極易腐蝕，如何將砷化鎵表面的光生電洞送至電解液便至關重要。

因此本篇論文的研究方向是先分析砷化鎵在中性 (0.1M Na2SO4)、鹼性(0.1M KOH)電解液中的特性。了解其腐蝕機制、腐蝕電位和腐蝕產物，藉此分析如何有效抑制腐蝕並同時進行水分解。而後在光輔助電鍍NiMo催化劑修飾砷化鎵表面，進而提升水氧化能力並抑制光腐蝕。

關鍵詞：光電化學、砷化鎵、光腐蝕、腐蝕電位、鎳鉬催化劑

Gallium arsenide(GaAs) has a suitable bandgap (1.43 eV) for spectrum absorption. In addition, it can also provide some photovoltaic which reduces the overvoltage of water splitting. However, photo-corrosion occurs when the holes are accumulated at gallium arsenide surface. It causes either decomposition or the formation of an insulating oxide layer in different electrolyte. In this study, we divided our research into two parts. First, we attempted to clarify the corrosion mechanism of bare n-GaAs in neutral and alkaline electrolyte. Next, we grew NiMo catalyst on the surface of n-GaAs by photo-assisted electrodeposition to improve the performance in PEC. We observed that GaAs with NiMo photoanodes could inhibit photo-corrosion and reduce overvoltage in solar water splitting reactions. In catalyst optimization research, we found that NiMo catalyst provides good OER enhancement. Furthermore, after NiMo catalyst is annealed under oxygen, it has the better OER ability because NiMo is completely oxidized. Stability tests had shown that the NiMo catalyst can enhance its oxygen Faraday’s efficiency in some degree. This means that NiMo catalyst can increase water oxidation current and inhibit semiconductor corrosion to a certain degree. However, it is still necessary to further improve the uniformity of the catalyst from exposing to the electrolyte.

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