Chemisorption of NO on Pd single crystals studied by UPS, AES and XPS

Abstract

The chemisorption of NO on Pd(100) was studied by uv photoelectron spectroscopy (UPS), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS), and was compared with that on Pd(111). The UPS results showed that the peaks derived from atomic N and O were found for NO-saturated. Pd(100) at room temperature. The NO-derived peaks disappeared at about 350 K and the N- and/or O-derived peak increased in intensity with increasing temperature. Signals from adsorbed N and NO were also found at 397.0 and 400.4 eV in the N(1s) XP spectra, respectively, at room temperature. The N(KLL) intensity increased for sample temperature increasing up to 360 K, began to decrease at 540 K and disappeared at 800 K. For the O(KLL) intensity, the corresponding temperatures above were 360, 730 and 920 K, respectively. The results obtained here suggest that a considerable amount of NO on Pd(100) dissociates into N and O contrary to the case of Pd(111), and that the N and O partially diffuse into the bulk, the oxygen forming a palladium oxide layer at room temperature. The nitrogen in the bulk diffuses back to the surface at higher temperatures.