STRUCTURAL EFFECTS ON WATER FORMATION FROM COADSORBED H+O ON RH(100)

被引:23
作者
GREGORATTI, L
BARALDI, A
DHANAK, VR
COMELLI, G
KISKINOVA, M
ROSEI, R
机构
[1] SINCROTRONE TRIESTE,I-34012 TRIESTE,ITALY
[2] UNIV LIVERPOOL,IRC SURFACE SCI,LIVERPOOL L69 3BX,MERSEYSIDE,ENGLAND
[3] UNIV TRIESTE,DIPARTIMENTO FIS,I-34127 TRIESTE,ITALY
关键词
ADATOMS; HYDROGEN; LOW ENERGY ELECTRON DIFFRACTION (LEED); OXYGEN; RHODIUM; SURFACE CHEMICAL REACTION; THERMAL DESORPTION SPECTROSCOPY; WATER; X-RAY PHOTOELECTRON SPECTROSCOPY;
D O I
10.1016/0039-6028(95)00695-8
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The effect of adsorbate coverage, adsorption sequence and temperature on the structure, composition and reactivity of coadsorbed layers, produced by dissociative adsorption of O-2 and H-2 at 200 K on a Rh(100) surface, has been studied by combined TPD, XPS and LEED measurements. The emphasis is on the impact of the structure and composition of the mixed O + H layers on the synthesis of hydroxyl and water as a result of the O + H surface reaction. The difference in the O Is binding energies of adsorbed O (529.9 eV) and OH species (530.8 eV) was used as a fingerprint to monitor the formation of the OH species. The H,O TPD spectra show substantial variations of the desorption temperature range and the amount of water evolved with coadsorbate coverage and structure: from 270 to 350 K and from 0 to 0.08 ML, respectively. It has been found that dense O + H adlayers, where the O coverage is in the range 0.25-0.4 ML, favor the formation of stable OH species. The maximum amount of stable hydroxyl OH species (similar to 0.16 ML) can be produced by heating of these dense adlayers to similar to 260 K. This results in reordering of the adspecies to form a new O + OH - (2 X 6) structure, where hydroxyls react readily to evolve 0.08 ML of water in a sharp desorption peak at similar to 280 K. The effect of the adlayer density and restructuring on the production of OH and H2O is discussed.
引用
收藏
页码:205 / 214
页数:10
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