Effect of preadsorbed oxygen on the adsorption of CO on Ir(110)

被引:31
作者
Burghaus, U
Ding, JQ
Weinberg, WH
机构
[1] Department of Chemical Engineering, Univ. of California at Santa Barbara, Santa Barbara
基金
美国国家科学基金会;
关键词
catalysis; adsorption probability; physical site blocking; carbon monoxide; oxygen; iridium; Ir(110); molecular beams;
D O I
10.1016/S0039-6028(97)00290-2
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
We report measurements of the initial adsorption probability S-0 as well as its coverage dependence S(theta(CO)) of CO on clean and oxygen-precovered Ir(110) for adsorption temperatures T-s below the onset of CO2 formation. The impact energy (1.3<E(0)24 kcal mol(-1)), the oxygen precoverage theta(O), and the surface temperature (85<T-s<200 K) were varied. The initial adsorption probability for CO on the clean surface decreases linearly with increasing impact energy E-0, and is independent of T-s. The shape of the S(theta(CO),E-0) curves points to non-activated precursor-mediated adsorption kinetics for low impact energies; for E-0 greater than or equal to 20 kcal mol(-1), direct adsorption events also contribute to the overall adsorption probability. For high impact energies (E-0>3 kcal mol(-1)), S-0(theta(0)) decreases almost linearly with increasing oxygen precoverage. However, for low impact energies (E-0<3 kcal mol(-1)), S-0(theta(0)) remains constant at 0.92+/-0.03 independent of theta(0). The results suggest a physical site blocking mechanism. No significant temperature dependence of S-0(theta(0)) was observed below the onset of CO oxidation. (C) 1997 Elsevier Science B.V.
引用
收藏
页码:L869 / L874
页数:6
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