Dopants adsorbed as single atoms prevent degradation of catalysts

被引:199
作者
Wang, SW
Borisevich, AY [1 ]
Rashkeev, SN
Glazoff, MV
Sohlberg, K
Pennycook, SJ
Pantelides, ST
机构
[1] Oak Ridge Natl Lab, Condensed Matter Sci Div, Oak Ridge, TN 37831 USA
[2] Vanderbilt Univ, Dept Phys & Astron, Nashville, TN 37235 USA
[3] Alcos Tech Ctr, Alcoa Ctr, PA 15069 USA
[4] Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA
基金
美国国家科学基金会;
关键词
D O I
10.1038/nmat1077
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
The design of catalysts with desired chemical and thermal properties is viewed as a grand challenge for scientists and engineers(1). For operation at high temperatures, stability against structural transformations is a key requirement. Although doping has been found to impede degradation, the lack of atomistic understanding of the pertinent mechanism has hindered optimization. For example, porous gamma-Al2O3, a widely used catalyst and catalytic support(2-6), transforms to non-porous alpha-Al2O3 at similar to1,100 degreesC(refs 7-10). Doping with La raises the transformation temperature(8-11) to similar to1,250 degreesC, but it has not been possible to establish if La atoms enter the bulk, adsorb on surfaces as single atoms or clusters, or form surface compounds(10-15). Here, we use direct imaging by aberration-corrected Z-contrast scanning transmission electron microscopy coupled with extended X-ray absorption fine structure and first-principles calculations to demonstrate that, contrary to expectations, stabilization is achieved by isolated La atoms adsorbed on the surface. Strong binding and mutual repulsion of La atoms effectively pin the surface and inhibit both sintering and the transformation to alpha-Al2O3. The results provide the first guidelines for the choice of dopants to prevent thermal degradation of catalysts and other porous materials.
引用
收藏
页码:143 / 146
页数:4
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