鈷摻雜釕基催化劑於電催化析氫反應之研究

Abstract

近年來能源議題已成為熱門研究主題，如何從自然界中有效獲取並儲存各種再生能源將會成為舒緩能源需求的關鍵。以太陽能為例，日光通過光電效應以光子撞擊太陽能板放出光電子，使得光能得以轉化為電能的形式，然而，電能的長途運輸不是那麼容易，這時需要再將電能轉化為更方便運輸的形式。透過電解反應以電能驅動溶液進行化學反應使我們得以在陰極、陽極獲得對應之產物，其中電解水便是一種能有效將電能儲存成化學鍵鍵能的手段。在電解水的過程中得到的陰極產物，氫氣，具有高能量密度且燃燒無汙染的優勢，藉由開發出優秀的陰極與陽極端電催化劑便能降低電解水過程中的能量損耗進而提高能量轉化效率。 本研究藉由尿素水解反應將含釕、鈷之前驅物合成在導電碳布上，再以管爐在氬氣環境下進行磷化反應合成一系列磷化釕鈷之碳布元件。藉由添加鈷金屬進入磷化釕後，相較於純的磷化釕無論是在酸性還是鹼性下催化都得到顯著的性能提升，尤其是在酸性電解液中，鈷的添加改善了磷化釕材料過電位較鹼性電解液高出許多的缺點，將本材料在酸性電解液中的過電位降低至鉑催化劑的催化活性，以及維持鹼性溶液中磷化釕的塔菲爾斜率與過電位，並且在全酸鹼值範圍都擁能保持相當優異的催化能力。此外為了瞭解電催化劑在施加電壓在水溶液中進行電催化反應時的結構以及原子區域結構，本研究除了基本的材料鑑定之外也輔以臨場X光吸收光譜與X光繞射實驗監控催化劑在真實催化條件下之材料結構變化，連結電化學量測中觀察到的現象，說明如何藉由添加鈷金屬調控釕基催化劑的催化活性。

Energy issues have attracted increasing attention in recent years due to the global warming and climate change. To avoid deterioration of greenhouse effect, clean energy sources should be developed to replace fossil fuels. Among numerous techniques which are able to extract energy from the nature, conversion of solar energy to electricity via photoelectric effect is a feasible method to utilize the energy from sunlight. However, delivery and storage of obtained electricity from sunlight may be challenging. To store electricity in another form, conversion of energy to chemical bonding through water electrolysis provides zero-pollution and high energy density fuel. The energy conversion efficiency can be enhanced by lowering the overpotential of anodic and cathodic catalysts. In this work the ruthenium-based catalysts were synthesized on carbon cloth by a two-step process: urea hydrolysis chemical bath deposition followed by chemical vapor deposition using phosphine (PH3) gas. With the addition of cobalt cation, enhancement on catalytic activity is observed especially in acidic media. Numerous techniques including in situ XAS, XRD are applied to monitor the genuine behaviors of materials under reaction conditions. Hence, the reaction mechanism can be unraveled. Our catalyst exhibits extremely small overpotential at 10 mA cm-2 of current density (3 mV in 0.5 M H2SO4 solution; 4 mV in 1.0 M KOH solution; 30 mV in 1.0 M PBS solution). Besides, the catalyst possesses high stability of electrocatalytic activity and material structure in catalytic process. These performances outperform all the other HER electrocatalysts, including benchmark of HER, Pt/C.