Abstract:
Metal oxide-supported nanoparticles of the platinum group metals Pt, Rh and Pd were studied
at ambient temperature and atmosphere using Kelvin probe force microscopy. In all cases, the
results reveal electron transfer from the metal to the oxide support which decreases in the
order TiO2 > CeO2 >> Al2O3, leading to charge polarization at the Schottky type interfaces
analogous to that of a parallel plane capacitor. This polarization cancels out to a large extent
for the Kelvin signal. On top of this there is a much smaller number of positive charges at the
outer catalyst particle surface, compensated by negative charges near the oxide surface. They
show the same trend over the different oxides. These charges determine the constant electrical
potential of the metal and are suggested to be the important component of the electronic
catalytic metal-support interaction which are known to be much stronger for reducible than
for non-reducible oxides.
