Existing models for the analysis of Kelvin probe microscopy experiments are extended and
used to analyze the experimental electrical potential profiles for a Pt/TiO2 model nanoparticle.
The derived model reproduces in detail the Kelvin probe image that reveals a characteristic
ring-shaped negative charge zone at the surface around the particle: A planar negative charge
zone at the surface of the support extends beyond the diameter of the Pt particle. It is
compensated mostly by a planar layer of positive charges in the metal across the interface,
and by a smaller number of positive charges at the metal-air interface. These latter charges
determine the positive electrical potential of the metal particle, and they are likely responsible
for the extent of the metal-support interaction in catalytic reactions.