Free radical reactions at the Ru(0 0 0 1) surface: Atomic oxygen and dissociated NH 3

• Published in: Surface science Vol. 603; no. 16; pp. 2469 - 2473
• Main Authors: Manandhar, Sudha, Gaddam, Sneha Sen, Kelber, Jeffry
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 2009
• Subjects: Ammonia; Atomic oxygen; Oxidation; Reduction; Ruthenium; XPS; Ammonia; Reduction; Ruthenium; Atomic oxygen; Oxidation; XPS
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/j.susc.2009.05.021

X-ray photoelectron spectroscopy was used to study the effect of atomic oxygen on Ru(0 0 0 1), and the effect of dissociated ammonia on RuO 2/Ru(0 0 0 1), in UHV conditions at ambient temperature. The Ru(0 0 0 1) surface was exposed, at ambient temperature, to a mixed flux of atomic and molecular oxygen generated by dissociation of O 2 in a thermal catalytic cracker, with ∼45% dissociation efficiency. The detailed study of the XPS spectra shows the formation of a disordered multilayer oxide (RuO 2). No formation of higher oxides of Ru was observed. The formation of RuO 2 proceeded without saturation for total oxygen exposures of up to 10 5 Langmuir, at which point an average oxide thickness of 68 Å was observed. RuO 2 formed by the reaction with atomic oxygen was exposed to a flux of NH x ( x = 1, 2) + H generated by the cracker. The reduction of RuO 2 to Ru metal was observed by XPS. An exposure of 3.6 × 10 2 L of NH x + H, resulted in the observation of adsorbed H 2O and OH, but no evidence of lattice oxide. The chemisorbed species were removed by additional NH x + H exposure. No nitrogen adsorption was observed.