Structure and NO reactivity of Zr-deposited Pd surfaces

The structure and NO reactivity of Zr-deposited Pd surfaces were investigated by X-ray photoelectron spectroscopy, low-energy electron diffraction, infrared reflection absorption spectroscopy, and temperature-programmed desorption. Zr on Pd(1 0 0) was oxidized to ZrO2 by exposure to O2 at 773 K. Heating at 823 K in a vacuum led to decomposition of ZrO2 to Zr metal and O2. The activation energy for ZrO2 decomposition changed remarkably at ΘZr = 0.4. For ΘZr > 0.4, a hexagonal structure was observed for ZrO2/Pd(1 0 0); no ordered structure was observed for ΘZr < 0.4. Deposited Zr had no significant effect on the adsorption and decomposition of NO on Pd(1 0 0) but resulted in a creation of new NO dissociation sites on Pd(3 1 1). Zr on Pd(3 1 1) was oxidized to ZrOX by oxygen produced from NO dissociation. Heating at 823 K in a vacuum led to decomposition of ZrOX to Zr metal and O2.