Two-Channel Decomposition of Methanol on Pt Nanoclusters Supported on a Thin Film of Al2O3/NiAl(100)

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• 作者：Chen-Sheng Chao ; Yu-Da Li ; Bo-Wei Hsu ; Won-Ru Lin ; Hsin-Chung Hsu ; Ting-Chieh Hung ; Chao-Chuan Wang ; Meng-Fan Luo
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：March 21, 2013
• 年：2013
• 卷：117
• 期：11
• 页码：5667-5677
• 全文大小：591K
• 年卷期：v.117,no.11(March 21, 2013)
• ISSN：1932-7455

文摘

The decomposition of methanol on Pt nanoclusters grown from vapor deposition onto an ordered Al₂O₃/NiAl(100) thin film was investigated under ultrahigh vacuum conditions with various surface probe techniques. The Pt clusters had mean diameter near 2.3 nm and height 0.4 nm before their coalescence; consisting of phase fcc, the clusters grew with their facets either (111) or (001) parallel to the 胃-Al₂O₃(100) surface, depending on the temperature of growth. More than half the adsorbed monolayer of methanol on the Pt clusters decomposed via two channels: dehydrogenation to CO and C鈥揙 bond scission. The dehydrogenation was dominant and induced first at low-coordinated Pt sites, at 150 K on Pt(001) clusters and 200 K on Pt(111) clusters, whereas both low-coordinated and some terrace Pt sites exhibited reactivity, despite the cluster size. On average, one CO was produced per surface Pt site, for a monolayer of methanol on either Pt(111) or Pt(001) clusters. In the other reaction, scission of the C鈥揙 bond occurred primarily in methanol itself and began about 250 K; the intermediate methyl preferentially formed methane on combining with atomic H from dehydrogenated methanol. No preferential reaction site for the C鈥揙 bond scission is indicated, but this process showed a remarkable dependence on the size and lattice parameter of the clusters: the probability of C鈥揙 bond scission decreased when the size increased and the lattice parameter decreased.