The Structure and Reactivity of Al2O3-Supported Cobalt−Palladium Particles: A CO-TPD, STM, and XPS Study
The Structure and Reactivity of Al2O3-Supported Cobalt−Palladium Particles: A CO-TPD, STM, and XPS Study
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DOI：
10.1021/jp021966v
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发表时间：
2003
影响因子：
3.3
通讯作者：
A. Carlsson;M. Naschitzki;M. Bäumer;H. Freund
中科院分区：
文献类型：
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作者：
A. Carlsson;M. Naschitzki;M. Bäumer;H. Freund
双金属Co - Pd Fischer - Tropsch催化剂在Co -氢化和甲烷转化方面表现出更高的活性。建立了Fischer - Tropsch催化剂的模型，并在超高真空条件下进行了研究。利用扫描隧道显微镜（STM）、Co的程序升温解吸（TPD）和x射线光电子能谱（XPS）研究了氧化铝薄膜上Co−Pd双金属颗粒的形貌、生长模式、暴露的结合位点和电子性能。Co和Pd的顺序沉积形成了核-壳结构。三层中空的场地很容易拆除，而顶部的场地在双金属外壳形成后具有统计弹性。CO与每一种金属的结合能因另一种金属的存在而降低。Pd 3d能级向更高结合能的移动同时Co 2p能级向更低结合能的移动表明电荷的净极化或d带态的重新分配。
Bimetallic Co−Pd Fischer−Tropsch catalysts have shown increased activity toward CO-hydrogenation and methane conversion. A model for these Fischer−Tropsch catalysts has been constructed and studied under ultrahigh vacuum conditions. The morphology, growth modes, exposed binding sites, and electronic properties of Co−Pd bimetallic particles supported on a thin alumina film have been studied using scanning tunneling microscopy (STM), temperature-programmed desorption (TPD) of CO, and X-ray photoelectron spectroscopy (XPS). Sequential deposition of Co and Pd results in a core−shell structure. Three-fold hollow sites are easily dismantled, whereas atop sites are statistically resilient upon the formation of a bimetallic shell. The binding energy of CO to each of the metals is lowered by the presence of the other. A shift in the Pd 3d level to higher binding energy concurrent with a shift in the Co 2p level to lower binding energy suggests a net polarization of charge or redistribution of d-band states.