Surface characterization of Au/HY by Xe-129 NMR and diffuse reflectance IR spectroscopy of adsorbed CO. Formation of electron-deficient gold particles inside HY cavities
Surface characterization of Au/HY by Xe-129 NMR and diffuse reflectance IR spectroscopy of adsorbed CO. Formation of electron-deficient gold particles inside HY cavities
复制标题
DOI：
10.1039/a703431h
复制
发表时间：
1997-10-07
期刊：
影响因子：
--
通讯作者：
Fraissard, J
中科院分区：
文献类型：
--
作者：
Guillemot, D;Borovkov, VY;Fraissard, J
用透射电子显微镜、Xe-129核磁共振和CO吸附漫反射红外光谱研究了[Au(En)(2)](3+)在423K的惰性气流中自动还原制备的Au/HY(4wt.%)体系。80%的金属团簇的尺寸在1-4 nm之间，平均线径为2.6 nm。还观察到一些大颗粒(~gt；5 nm)。氙气吸附和Xe-129核磁共振谱证实了HY腔内存在金团簇，并清楚地表明金团簇是氙弱吸附中心。Xe-129核磁共振谱显示了颗粒大小分布的不均一性。漫反射红外光谱显示，CO在金表面有一个强烈的不对称吸收带，它是线性吸附的。约2110-2120和2170 cm(-1)的两个弱肩部分别归属于中性颗粒和氧化金位置。首次观察到吸附在金表面的CO在2140 cm(-1)处的主要吸收带，这是由于CO物种与HY晶格内的缺电子金颗粒Au-n(sigma+)相互作用并与质子接触所致。CO在这些Au-n(sigma+)粒子上的吸附比在其他金位上更强，即使在室温下抽真空30min，也观察到了相应的红外伸缩振动。
The Au/HY (4 wt.%) system, prepared by autoreduction of [Au(en)(2)](3+) in inert gas flow at 423 K, has been studied by TEM, Xe-129 NMR and diffuse reflectance infrared spectroscopy of adsorbed CO. 80% of the metallic clusters were in the 1-4 nm size range, and the average linear diameter was found to be 2.6 nm. Some large particles (>5 nm) were also seen. Xenon adsorption and Xe-129 NMR spectroscopy proved the presence of gold clusters inside HY cavities and showed clearly that gold clusters are weak adsorption sites for xenon. Heterogeneity in the particle size distribution was suggested by Xe-129 NMR spectroscopy. Diffuse reflectance IR spectroscopy showed an intense asymmetric absorption band of CO linearly adsorbed on the gold surface. Two weak shoulders at ca. 2110-2120 and 2170 cm(-1) were ascribed to neutral particles and oxidized gold sites, respectively. The main absorption band at about 2140 cm(-1) is observed for the first time for CO adsorbed on a gold surface and was attributed to CO species interacting with electron-deficient gold particles Au-n(sigma+) inside the HY lattice and in contact with protons. CO was more strongly adsorbed on these Au-n(sigma+) particles than on other gold sites; the corresponding IR stretching vibration was observed even after evacuation for 30 min at room temperature.