The structure and reactivity of Al2O3-supported cobalt-palladium particles:: A CO-TPD, STM, and XPS study

被引:87
作者
Carlsson, AF [1 ]
Naschitzki, M [1 ]
Bäumer, M [1 ]
Freund, HJ [1 ]
机构
[1] Max Planck Gesell, Fritz Haber Inst, Dept Chem Phys, D-14195 Berlin, Germany
关键词
D O I
10.1021/jp021966v
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
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.
引用
收藏
页码:778 / 785
页数:8
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