The ESCA technique has been employed to characterize various palladium-oxygen species on the surface of oxidized palladium metal. Both oxygen-chemisorbed palladium atoms (PdOads) and PdO are observed on metal substrates exposed to air at 600 to 900 °C. These results have been applied to studying electrochemically oxidized palladium electrodes in 1N H2SO4. Both PdO and PdO2 are observed at potentials beginning at +0.90 V vs. N.H.E. In addition, since the mean escape depth of the photoelectron is on the order of 10 Å, estimates of oxide film thicknesses can be made. Electrodes oxidized at 0.9 V had a coating about 5 Å thick whereas at 1.7 V, the thickness increased to greater than 40 Å. By examining the peak areas of the Pd spectra and the oxygen spectra, the presence of excess oxygen as adsorbed and H2O, hydrated PdO, PdO2, and Pd(OH)2 or Pd(OH)4 was clearly indicated.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry