The interaction of catalytically active metal particles with supporting oxide surfaces is still an actual topic in catalysis. Particularly, the exact role of sites at the metal-support boundary is not entirely clear. Here we demonstrate a long-range effect of metal-oxide boundaries of Pd/ZrO2 and Rh/ZrO2 model systems on the reactivity of Pd and Rh in CO and H2 oxidation reactions. The effect was directly observed by a photoemission electron microscope (PEEM), used as a flow reactor in the 10-6 mbar pressure range. The kinetics by imaging approach allowed evaluation of reaction kinetics for individual supported particles within the resolution limit of PEEM, whereas the activation and deactivation fronts (chemical waves) were used to probe the metal/oxide interface contribution. The observations show that the atomically narrow (&lt;1 nm) interface between metallic Pd or Rh and ZrO2 causes a remarkable shift in the kinetic behaviour even of µm-sized particles, i.e. affecting metal sites thousands of nanometers away from the interface. The effect is attributed to the critical role of the perimeter sites for the initiation of kinetic transitions from the inactive to active state and vice versa, due to the modified binding energy of oxygen at the sites along the metal/oxide interface. The kinetic transitions initiated locally at the metal/oxide boundary are then transmitted over the entire Pd or Rh particles.

Long-ranging metal/oxide interface effects for ZrO2 supported Pd and Rh particles

2019 Fall National Meeting

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