ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The surface mobilities of both CO and K coadsorbed on Ru(001) were studied using laser-induced thermal desorption (LITD) techniques. The LITD measurements revealed that CO was essentially immobile on the potassium-promoted Ru(001) surface when the CO surface coverage, aitch-thetaCO, was less than the potassium coverage, aitch-thetaK. The CO surface mobility increased dramatically when aitch-thetaCO(approximately-greater-than)aitch-thetaK. At aitch-thetaK=0.10 ML and 315 K, the CO diffusion coefficient was DCO〈4×10−10 cm2/s for aitch-thetaCO〈0.10 ML and increased to DCO=2.5×10−7 cm2/s for aitch-thetaCO(approximately-greater-than)0.10 ML. At aitch-thetaK=0.25 ML and 315 K, the CO surface diffusion coefficient was DCO〈4×10−10 cm2/s for aitch-thetaCO〈0.25 ML and increased to DCO=5×10−9 cm2/s for aitch-thetaCO(approximately-greater-than)0.25 ML. The potassium surface mobility also decreased dramatically as a function of CO coverage at both aitch-thetaK=0.10 ML and aitch-thetaK=0.25 ML. These diffusion results are consistent with a mutually stabilizing and trapping interaction between coadsorbed CO and K with a 1:1 CO:K stoichiometry. The thermal desorption spectra of both CO and K were also studied using temperature programmed desorption (TPD) techniques. At aitch-thetaK=0.10 ML and CO coverages ranging from aitch-thetaCO=0.06 ML to aitch-thetaCO=0.42 ML, CO TPD peak temperatures were consistently higher than CO peak temperatures obtained on clean Ru(001). These TPD results indicate that CO is stabilized by K on Ru(001). In addition, the potassium TPD spectra at various CO coverages with aitch-thetaK=0.10 ML and aitch-thetaK=0.25 ML revealed that K was stabilized by coadsorbed CO. The experimental results for CO and K coadsorbed on Ru(001) argue for a mutually stabilizing, short-ranged trapping CO–K interaction with a 1:1 CO:K stoichiometry. Monte Carlo simulations based on this model for the CO:K interaction were also consistent with the coadsorbate surface diffusion results. © 1996 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.471398
