AU, CU, AG, NI, AND PD PARTICLES GROWN IN SOLUTION AT DIFFERENT ELECTRODE-POTENTIALS

The multiply twinned particles (MTPs) of Cu, Ni, Ag, and Pd formed on an electrode in solution at low electrode potentials were systematical ly studied by means of transmission electron microscopy (TEM). At low electrode potentials the icosahedral and dedahedral particles were obs erved for gold, silver, and palladium, but only the decahedral particl es were observed for copper and nickel. The icosahedral particles of c opper and nickel are less stable compared to the decahedral particles. The decahedral Ag particles were oxidized during the observation by T EM and changed into Ag2O having fee structure. The stability of these transition metal MTPs formed in solution is in the sequence Au > Ag > Cu and Pt > Pd > Ni. The differences of d-s hybridization or s,p-d hyb ridization among 3d, 4d, and 5d transition metals will increase the su rface electron density, which results in the contraction of the lattic e in the lateral direction. The decahedral and icosahedral particles o f Au were formed on an SnO2 electrode, which indicates that the MTPs o f Au are grown not only on carbon film but on SnO2 film depending on t he electrode potential.