| 摘要: | 在本研究中，為了增益白金基催化劑之乙醇氧化反應(ethanol oxidation reaction, EOR)的活性，系統性的合成碳支撐之鉑基催化劑，包含鉑(Pt)、鉑釕(PtRu)、鉑銠(PtRh)以及鉑釕銠(PtRuRh)之奈米棒，並探討一維結構對EOR活性之增益的效果。所製備觸媒之組成、結構、形貌、表面組成、電化學性質分析分別藉由熱場發射掃描式電子顯微鏡-微區元素能量分析儀、X光繞射分析儀、穿透式電子顯微鏡、X光電子能譜儀(X-ray photoelectron spectroscopy, XPS) / 氫氣程溫還原系統(H2-temperature programmed reduction, TPR)、循環伏安法 (cyclic voltammograms) / 線性掃描伏安法 (linear sweep voltammograms) / 計時伏安法(chronoamperometric, CA)進行檢測與分析。
本研究結果分成兩個部分，第一部分是利用甲酸還原法製備長寬比約為4.6的鉑基奈米棒。並藉由XPS與TPR的分析可得知Pt80Ru3Rh17在表面具備同時具備PtOx, RuOx和RhOx三種含氧物種(oxygen containing species, OCS)，且在0.6 V時能提供較高的電流值，說明其表面的OCS可藉由雙功能機制來促進乙醇吸附於鉑表面以提升活性；另外CA的結果也指出Pt80Ru3Rh17觸媒相較於其他觸媒展現出最佳的活性和穩定性，也可以歸功於表面OCS的作用，氧化了CO或是CHx等吸附於鉑表面的中間產物，避免鉑催化劑被毒化。
第二部分則是探討不同長寬比的鉑釕銠奈米棒對於EOR活性之影響，藉由不同的溫度和成長天數，可成功製備出長寬比分別為4.7, 6.5和8.1的三元Pt80Ru3Rh17。在EOR活性檢驗中，具有最高長寬比的三元PtRuRh觸媒在0.6 V 的電流密度都高於其他兩者；此外，在2小時的CA測試後，最大長寬比之奈米棒同樣顯示了最佳之活性，此結果可歸因於擁有較大長寬比之奈米棒能協助表面OCS形成，促進移除吸附於表面之中間產物。由以上成果可知，控制催化劑的形貌是一有效提升EOR活性之方法。
;In this study, in order to enhance the EOR activity, carbon-supported Pt-based catalysts, including PtRu, PtRh, and PtRuRh nanorods (NRs) have been prepared, and the effect of 1-Dimensional structures on the EOR activity has been investigated. The compositions, structures, morphologies, surface compositions and electrochemical properties of prepared catalysts are analyzed by Field-Emission scanning electron microscope and X-ray energy dispersive spectrometer, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) / H2-temperature programmed reduction (TPR) and cyclic voltammograms (CV) / linear sweep voltammograms (LSV) / chronoamperometric (CA).
This study is divided into two parts. In the first part, formic acid method has been used to prepare Pt-based NRs with an aspect ratio of 4.6. XPS and TPR results confirm that ternary Pt80Ru3Rh17can possess oxygen containing species (OCS) including PtOx, RuOx and RhOx onto the surface simultaneously and with high current density at 0.6 V, indicating that the surface OCS can promote the adsorption of ethanol through bi-functional mechanism and thereby enhance the EOR activity. On the other hand, CA results suggest that the ternary Pt80Ru3Rh17 have the highest current density and stability compared to other prepared catalysts, which can be attributed to that the surface OCS help the oxidation of adsorbed intermediates, such as CO or CHx, preventing Pt active sites from poisoning.
In the second part, the effect of aspect ratios on the EOR activity of PtRuRh NRs has been investigated. The Pt80Ru3Rh17NRs with an aspect ratio of 4.7, 6.5 and 8.1 have been prepared at different temperatures and times. The EOR activity of ternary PtRuRh which possess the largest aspect ratios at 0.6 V is the highest and present the best performance after CA test for 2 hrs, because NRs with large aspect ratios are able to assist the formations of OCS, promoting the removal of adsorbed intermediates. Based on the above results, we have demonstrated that controlling the morphologies is an effective method to enhance EOR performance. |
