| Summary: | 碩士 === 國立中央大學 === 物理學系 === 107 === 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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