Transitional metal(TM)and noble metal(NM)nanoparticles supported on appropriate substrates have been extensively used as efficient and economical catalysts in many industrial applications,such as CO oxidation in vehicle emission reduction,Water-gas shift reaction,and hydrogenation.However,the intrinsic catalytic activities and selectivity of these supported metal particles are strongly size-and geometrydependent,particularly at nanometer and sub-nanometer scales.