Vital role of moisture in the catalytic activity of supported gold nanoparticles
Vital role of moisture in the catalytic activity of supported gold nanoparticles
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DOI：
10.1002/anie.200453796
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发表时间：
2004-04-04
影响因子：
16.6
通讯作者：
Haruta, M
中科院分区：
文献类型：
--
作者：
Daté, M;Okumura, M;Haruta, M
为什么惰性金只有在以纳米颗粒的形式分散时才能具有催化活性？这个简单的问题不仅在催化和工业化学领域引起了越来越多的兴趣，[1 - 4]而且在簇合物和理论科学领域也引起了越来越多的兴趣。[5-7]为了回答这个问题，CO氧化作为一个模型反应进行了深入研究。[8 - 14]已知反应物气体中的水分对反应有很大影响。[10然而，只有少数最近的研究讨论了考虑水的反应机理。[16 1989年首次报道了沉积在金属氧化物载体上的金纳米颗粒形成活性催化剂。[8]负载型Au催化剂不仅在低温下表现出显著的活性，[8]而且在水分存在下也表现出显著的活性。[15]这两个特征使得催化剂有利于在环境条件下，即中等温度和潮湿气氛下的应用，并导致其在1992年在日本用于厕所除臭的商业化。另一方面，基础研究通常在相对干燥的条件下进行。[5，11，13，14]因此，阐明水分的影响对于理解金的独特催化作用非常重要。金催化剂中水分的影响主要用于CO氧化[10，16]，因为反应温度极低（<273 K），而且水分的影响显著。然而，在迄今为止的大多数情况下，仅定性地研究了这种效应，即确定添加几摩尔百分比的水蒸气是否会增强或抑制反应。在这项研究中，我们使用了一种特殊的装置，可以将水蒸气控制在极低的水平，[19]并表明这种低水平仍然可以影响催化反应。
Why can inert gold become catalytically active only when dispersed in the form of nanoparticles?—This simple question has attracted growing interest in the field of not only catalytic and industrial chemistry,[1–4] but also cluster and theoretical science.[5–7] To answer this question, CO oxidation has been intensively studied as a model reaction.[8–14] The reaction is known to be greatly influenced by moisture in the reactant gas.[10, 15] However, only a few recent studies discuss the reaction mechanisms taking water into account.[16, 18] Even in these studies on the effect of moisture, for practical reasons, the addition of water vapor has been examined only at high concentrations.It was first reported in 1989 that gold nanoparticles deposited on metal-oxide supports form active catalysts.[8] Supported Au catalysts exhibit significant activity not only at low temperatures,[8] but also in the presence of moisture.[15] These two features make the catalysts advantageous for applications at ambient conditions, that is, moderate temperatures and humid atmospheres, and have led to their commercialization for odor removal in restrooms in Japan in 1992. On the other hand, fundamental studies are usually carried out under relatively dry conditions.[5, 11, 13, 14] Therefore, it is important to elucidate the effect of moisture to understand the unique catalysis of gold. The effect of moisture in gold catalysts has been investigated mainly for CO oxidation,[10, 16] because of the extremely low reaction temperature (< 273 K) and because of the remarkable effect of moisture. In most cases to date, however, the effect has been studied only qualitatively, that is, to determine whether the addition of a few mole percent of water vapor enhances or suppresses the reaction. In this study, we employ a special apparatus that allows the control of water vapor to extremely low levels,[19] and show that such low levels can still influence the catalytic reaction.