Oxidative steam reforming of ethanol on rhodium nanoclusters supported by graphene grown on Ru(0001)

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题名:	Oxidative steam reforming of ethanol on rhodium nanoclusters supported by graphene grown on Ru(0001)
作者:	黃怡誠;Huang, Yi-Cheng
贡献者:	物理學系
关键词:	氧化蒸氣重整;乙醇;銠;Oxidative steam reforming;Ethanol;Rhodium;water;oxygen
日期:	2019-02-26
上传时间:	2019-04-02 14:33:21 (UTC+8)
出版者:	國立中央大學
摘要:	我們研究以銠(Rhodium)奈米粒子作為催化劑鍍在graphene上用釕(Ruthenium)單晶作為基板，了解水(H2O)及氧氣(O2)在乙醇(Ethanol)的氧化蒸氣重整反應中如何扮演有效改變反應途徑的角色。並藉由熱脫附質譜儀(TPD)、紅外光反射吸收能譜(IRAS)與同步輻射光電子能譜(PES)表面探測技術在超高真空(UHV)的環境下進行表面量測。結果顯示，當有氧原子(O)預先吸附在銠奈米粒子表面上會促進乙醇的分解並改變反應途徑從純乙醇吸附藉由C-Hβ的斷鍵形成乙醇中間產物oxametallacycle (CH2CH2O)改變為藉由C-Hα的斷鍵形成乙醛(CH3CHO)，此變大大促進了氫氣(H2)的產生，也生成副產物一氧化碳(CO)及甲烷(CH4)。而隨著高氧原子覆蓋量的表面，反應途徑轉向為生成乙酸(CH3COO)，此改變抑制了氫氣的產生但也促進生成了二氧化碳。水以分子的狀態吸附在銠奈米粒子上並沒有分解且脫附溫度低於200 K。相反的，當氧原子預先吸附於銠奈米粒子金屬表面上，有大部分的水分解形成氫氧根(OH)及氧原子(O)且脫附溫度高於常溫300 K。在之後的乙醇的氧化蒸氣重整反應中水與氧的共同吸附對於反應的效率並沒有像氧預先吸附那樣有效且明顯的改變反應途逕及產量。;With rhodium-based catalysts, rhodium nanoclusters supported on graphene grown on Ru(0001) surface, we investigated how oxygen and water play effective roles in the oxidative steam reforming reaction of ethanol, under ultrahigh vacuum conditions and using temperature programmed desorption (TPD), infrared reflection adsorption spectroscopy (IRAS), synchrotron-based photoemission spectroscopy (PES). The result show that the atomic oxygen (O) on Rh surfaces promoted the decomposition of ethanol and altered the reaction pathway from the one via C-Hβ bond cleavage forming oxametallacycle to that via C-Hα bond cleavage forming acetaldehyde; the alternation high promoted the production of H2 along with the side products of CO, CH4. The reaction pathway shifted to acetate intermediates with higher oxygen content, which suppressed the production of H2 but promoted that of CO2. Water adsorbed molecularly on Rh surface; no water was dissociated and water desorbed below 200 K. In contrast, on atomic oxygen (O) pre-covered Rh surface, a great fraction of water molecules underwent dissociation into atomic hydrogen and hydroxyl groups (OH) and desorbed above room temperature 300 K. The OH on D2O/O-Rh clusters surface abstracted H from ethanol, like O* but did not altered the reaction pathway as effectively as O*－ the O2 effect in this aspect is more significant than the H2O one.
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