Decomposition of methanol on vanadium nanoclusters supported by graphene/Ru(0001) and Al2O3/NiAl(100)

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题名:	Decomposition of methanol on vanadium nanoclusters supported by graphene/Ru(0001) and Al2O3/NiAl(100)
作者:	武昱成;Wu, Yu-Cheng
贡献者:	物理學系
关键词:	釩;氧化鋁;石墨烯;催化;vanadium;Al2O3;graphene;catalysis
日期:	2018-03-28
上传时间:	2018-04-13 11:08:53 (UTC+8)
出版者:	國立中央大學
摘要:	甲醇的催化分解反應被廣泛的研究，是由於可以應用在甲醇燃料電池(DMFC)上，作為燃料電池的主要產物氫氣的供應來源，並有著提供高效率的電能轉換效率的未來展望。在甲醇燃料電池(DMFC)上的氫氣產量主要是由其甲醇催化反應所控制，因此對觸媒的反應動力學及反應能力與催化劑的結構的關係的相關知識是改善甲醇燃料電池催化分解反應的必備條件。為了研究重氫甲醇(CD3OD)在釩(Vanadium)奈米粒子鍍在graphene/Ru(0001) 及 θ-Al2O3/NiAl(100)兩種不同的基板上的催化分解反應，我們藉由熱脫附質譜(TPD)和紅外光反射吸收能譜(IRAS)表面探測技術在超高真空的環境下進行表面量測。當釩奈米粒子鍍在graphene/Ru(0001)上時甲醇並沒有任何的產物從表面脫附出來，包括CO及氫氣之類的甲醇分解的常見產物。但從紅外光反射吸收能譜卻可以觀察到C-O斷鍵在180 K時開始發生。吸附在樣品表面的甲醇看起來是有反應的，但缺沒有任何的產物從表面上脫附出來，可能是因為分解後的產物持續殘留在表面上。然而釩奈米粒子鍍在θ-Al2O3/NiAl(100)的反應路徑主要通過脫氫及C-O斷鍵。而C-O斷鍵的發生是在180 K左右，後續的氫氧根及甲基則會繼續經過脫氫形成C及O原子而持續殘留在表面上。而部分的甲基會與從甲醇脫氫下來的氫原子再結合形成甲烷並在400 K時脫附出來。 ;The catalytic decomposition of methanol (CH3OH) is extensively investigated because the principal reaction is applied in direct methanol fuel cells (DMFC), which offer a prospect of efficient conversion of methanol to electricity, and because it can serve as a source of hydrogen. As the performance of DMFC or the production of hydrogen is governed largely by the catalyzed reaction, a knowledge of the detailed reaction kinetics and a correlation between reactivity and structure of the catalysts are desirable. To respond to the demand, we investigated the adsorption and reaction of methanol-d4 (CD3OD) on vanadium (V) nanocluster supported on graphene grown on Ru(0001) single crystal and θ-Al2O3/NiAl(100), under ultrahigh vacuum conditions and with infrared reflection absorption spectroscopy and temperature programmed desorption. TPD results shows the distinct desorption of HD, D2 and methane from the surface around 400 K; there is no any CO desorption feature was found indicating CO bond scission along with dehydrogenation. The IRAS results show the C-O bond scission of methanol-d4 or methoxy start around 180 K. From TPD and IRAS results we have two different guess for the methanola-d4 reaction route on the V/Al2O3/NiAl(100). First, on the V surface the O-D bond scission happen and as the temperature reach to 180 K the C-O bond scission of methoxy takes place. The other guess is O-D bond scission after the C-O bond scission, thereafter; all the products dehydrogenated further to atomic oxygen, deuterium and carbon then diffused into V nanoclusters or substrate. For methanol-d4 on the V nanoclusters/graphene/Ru(0001), the TPD spectra show desorption of methanol-d4 only. Further, the vibration of CD3 from the IRAS spectra has a red shift reveal the C-O bond scission of methanol-d4. It seems that methanol-d4 decomposes on the V nanoclusters while all the products diffuse into the substrate.
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