Effects of palladium particle size and palladium silicide formation on Fourier transform infrared spectra and carbon monoxide adsorbed on palladium/silicon dioxide catalysts
Effects of palladium particle size and palladium silicide formation on Fourier transform infrared spectra and carbon monoxide adsorbed on palladium/silicon dioxide catalysts
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DOI：
10.1021/j100349a042
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发表时间：
1989-06
期刊：
影响因子：
--
通讯作者：
L. Sheu;Zbigniew Karpinski;W. Sachtler
中科院分区：
文献类型：
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作者：
L. Sheu;Zbigniew Karpinski;W. Sachtler
CO在SiO{sub2}负载的Pd上的两种主要吸附模式反映了不同程度的回馈作用，这至少部分是由吸附中心的局部电子密度控制的。随着Pd颗粒尺寸的增大，桥联模式(B)的CO含量增加，线形模式(L)的CO含量减少，表明密排晶面平台中Pd原子的电子密度较高，符合Smoluchowski的经典模型。对于300℃还原的样品，我们的数据点和其他作者的数据点位于B/L随金属分散度的共同曲线上。600℃下的大量还原导致B/L值显著降低，这归因于钯硅化物的初步形成。300℃氧化还原破坏了硅化物，B/L值恢复到原始曲线。
Two major modes of CO adsorption on SiO{sub 2}-supported Pd reflect different extents of back-donation, which is, at least in part, controlled by the local electron density at the adsorption site. The fraction of CO in the bridging mode (B) increases and that of the linear mode (L) decreases, with increasing size of the Pd particles, indicating high electron density at Pd atoms in terraces of close-packed crystal faces, in agreement with Smoluchowski's classical model. For samples reduced at 300{degree}C our data points and those of other authors are located on a common curve of B/L vs metal dispersion. Extensive reduction at 600{degree}C results in significantly lower B/L values, attributed to the incipient formation of a palladium silicide. Oxidation followed by reduction at 300{degree}C destroys the silicide, and the B/L value returns to the original curve.