Reductive routes to stabilized nanogold and relation to catalysis by supported gold
Reductive routes to stabilized nanogold and relation to catalysis by supported gold
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DOI：
10.1016/j.apcata.2005.05.038
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发表时间：
2005-09-18
影响因子：
5.5
通讯作者：
Scurrell, MS
中科院分区：
文献类型：
--
作者：
Boyd, D;Golunski, S;Scurrell, MS
提出并讨论了离子金（可能是Au(1+)）参与负载金催化反应的证据。各种催化体系和各种实验技术已用于涉及一氧化碳的反应。对金-钛和冷-钛-锆的穆斯堡尔效应谱分析表明，Au(0)、Au(I)和Au（III）同时存在，但只有Au(I)的含量与这些固体的CO氧化活性直接相关。XPS数据表明，相对于Au(0)，金-钛-锆催化剂中存在的一小部分金（约6%）处于缺电子状态。对于金-铁氧化物催化剂，在金（最初以Au（III）的形式存在）发生部分还原的样品中，获得了高的水气转换活性。对于金- hy沸石，其中金最初是通过[Au(en(2))]（3+）的离子交换作为Au（III）引入的，样品只有在超过相当长的诱导期后才具有催化活性。硼氢化钠预处理缩短了催化剂的诱导周期，提高了催化剂的活性，并对金进行了一定程度的还原。基于金-钛的活性CO氧化催化剂中存在非等量金（即金属金和离子金）的进一步证据是，当固体在氧化条件下用含氰化物离子的溶液处理时，会发生部分金的去除。当金含量降低时，单位金的比活度随金含量的降低而增加。结果与Au(I)参与催化反应的要求一致，尽管不排除Au(0)的作用。(c) 2005 Elsevier B.V.版权所有
Evidence is presented and discussed for the involvement of ionic gold, probably Au(1+) in catalysis by Supported gold. Various catalytic systems and various experimental techniques have been used for reactions involving carbon monoxide. Mossbauer effect spectroscopy on gold-titania and cold-titania-zirconia reveals the co-existence of Au(0), Au(I) and Au(III), but only the Au(I) content correlates directly with the activity of these solids for CO oxidation. XPS data suggest that a small (ca. 6%) fraction of the gold present in gold-titania-zirconia catalysts is present in an electron deficient state relative to Au(0). For gold-iron oxide catalysts, high water-gas shift activity is obtained for samples in which a partial reduction of the gold, initially present as Au(III), has occurred. For gold-HY zeolites, in which the gold is initially introduced as Au(III) by ion-exchange from [Au(en(2))](3+), samples become catalytically active only after a considerable induction period has been exceeded. The induction period is shortened and the activity of the catalysts increased by pre-treatment with sodium borohydride, and some degree of reduction of the gold is assessed to have occurred. Further evidence that non-equivalent states of gold exist (i.e. metallic and ionic gold) in active CO oxidation catalysts based on gold-titania is provided by the fact that partial removal of gold Occurs when the solids are treated with solutions containing cyanide ions under oxidative conditions. The specific activity per unit of gold increases with decreasing gold content when the gold content is lowered by such treatment. The results are consistent with the requirement for Au(I) involvement in the catalytic reaction, though a role for Au(0) is not ruled out. (c) 2005 Elsevier B.V. All rights reserved.