Colloids of Pt, Pt0.8Pd0.2, and
Pt0.2Pd0.8 particles of approximately 2.5
nm diameter with poly (N-vinyl-2-pyrrolidone) as protecting agent were dried, and the
195Pt NMR spectrum and nuclear spin−lattice
relaxation
rates were measured. The spectra indicate that the particles are
indeed bimetallic and that the composition
of their interior corresponds well to the nominal value. A strong
variation of catalytic activity of these systems
with composition around Pt0.2Pd0.8 has
been reported in the literature. We suggest that this effect is
related
to corresponding variations in the local densities of electronic states
at the Fermi energy on the surface sites
of the catalytic metal.