Charge Polarization at Catalytic Metal–Support Junctions. Part B: Theoretical Modeling of Kelvin Probe Force Microscopy

Existing models for the analysis of Kelvin probe microscopy experiments are extended and used to analyze the experimental electrical potential profiles for a Pt/TiO 2 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.