CHEMISORPTION OF NO ON PD(100), (111) AND (110) SURFACES STUDIED BY AES, UPS AND XPS

The adsorption state of NO on the Pd(100), (111) and (110) surfaces in the temperature range of 300-1100 K has been studied by Auger electron spectroscopy (AES), ultraviolet and X-ray photoelectron spectroscopy (UPS, XPS). The experimental results indicate that the adsorbed NO on the (100) surface dissociates partially into N and O atoms and part of the atoms diffuses into the bulk at room temperature. On the (110) and (111) surfaces, NO adsorbs molecularly at room temperature and part of the NO decomposes with a slight increasing of temperature and part of the N and O atom diffuses also into the bulk. The NO dissociation on the Pd surface and the diffusion into the bulk of the N and O atoms take place at lower temperature in the following order: (110), polycrystalline, (111) and (110) surface. On all surfaces, the back-diffusion to the surface of the N and O atoms in the bulk is caused by heating to higher temperature.