鉑系多元觸媒應用於直接甲醇與乙醇燃料電池電極活性探討

Abstract

本研究採用濺鍍法將鐵、鈷、鎳、銅、銀和鉑濺鍍於碳材顆粒以製備出鉑系多元觸媒層，進一步以去合金製程增進其活性表面積，探討應用於直接甲醇和乙醇燃料電池的催化活性和表現。 由掃描式電子顯微鏡和穿透式電子顯微鏡的結果得知鉑系多元觸媒層之顆粒大小約為30~80 nm；由能量散佈分析儀和感應式偶合電漿質譜儀得知藉由靶材鉑片放置數量和濺鍍時間可以控制鉑於觸媒層之含量，較多的鉑片數以及較長的濺鍍時間可使鉑的含量增加；藉X光繞射分析儀分析出鉑系多元觸媒層主要以鉑的面心立方結構成固溶體，經過去合金化製程後，鉑系多元觸媒依然與鉑面心立方結構形成固溶體，並以不同的去合金電壓區間分別探討去合金電壓對鉑系多元觸媒層之催化活性。經過電化學分析結果，鉑系多元觸媒於陽極反應在高鉑含量以及去合金電壓區間0~0.5 V(vs Ag/AgCl)有較佳的表現，而在陰極反應則在高鉑含量以及去合金電壓0~0.7 V有較好的催化活性。並藉由氫吸脫附實驗證實，經過去合金製程之鉑系多元觸媒確實可以得到提高電化學活化表面的結果以提高催化表現。

In this research, Pt-based multi-element catalysts were prepared by sputter -deposition of Fe, Co, Ni, Cu, Ag and Pt onto a carbon support and followed by electrochemical dealloying process to improve active sites of catalysts. Furthermore, the catalytic activity and performances of different catalysts in anodic methanol oxidation reaction (MOR), alcohol oxidation reaction (AOR) and cathodic oxygen reduction reaction (ORR) were also investigated. It was observed that nano-particles of all Pt-based multi-element catalysts were successfully prepared about 30~80 nm in size from SEM and TEM images. The EDX and ICP-MS results showed that as the sputtering time and Pt metal pieces on the sputtering target were increased, the catalysts had a tendency to become higher Pt composition loading. As the matter of fact, Pt-based multi-element catalysts appeared a solid solution with Pt (fcc) crystalline structure after XRD measurements, and so did the samples after dealloying. Under different applied dealloying voltage regions for dealloying process and analysis by cyclic voltammetry and polarization curve measurements, 0~0.5 V (vs Ag/AgCl) exhibited the better performance in MOR and AOR; while 0~0.7 V showed obviously high catalytic activity towards ORR. Relied on the results of hydrogen adsorption/desorption experiment, the Pt active sites would be increased after the dealloying process in order to lead the better performance behavior.