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 structures. In our laboratory, a type of nanometer particle of a transition metal with a rare-earth outer shell was synthesized by a hydrogen arc plasma method, and their microstructures were analyzed by TEM and an X-ray diffraction profile refinement method. The nanoparticles were used as a catalyst in some chemical reactions. The catalytic activities of the nanometer particles with and without a rare-earth thin shell were evaluated by means of the catalytic reactions of toluene, nitrobenzene hydrogenation, and carbon monoxide oxidation. The results of these chemical reactions demonstrated that the nanometer transition metal particles with a rare-earth outer shell possess much higher catalytic activity and selectivity than those particles without 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.