Thin-shell structure of nanometal particles

As is well known, the rare-earth and transition-metal elements are the main active components in catalysis because of their special d and f electron s tructures. In our laboratory, a type of nanometer particle of a transition metal with a rare-earth outer shell was synthesized by a hydrogen are plasm a method, and their microstructures were analyzed by TEM and an X-ray diffr action profile refinement method. The nanoparticles were used as a catalyst in some chemical reactions. The catalytic activities of the nanometer part icles with and without a rare-earth thin shell were evaluated by means of t he catalytic reactions of toluene, nitrobenzene hydrogenation, and carbon m onoxide oxidation. The results of these chemical reactions demonstrated tha t the nanometer transition metal particles with a rare-earth outer shell po ssess much higher catalytic activity and selectivity than those particles w ithout a rare-earth outer shell. This means that the rare-earth shell plays an important role in these chemical reactions. This catalytic mechanism of the rare-earth shell is discussed. (C) Elsevier Science Inc., 2000. All ri ghts reserved.