Surface Diffusion of Potassium Coadsorbed with CO on Ru(001):  A Coverage Grating−Optical Second Harmonic Diffraction Study

Abstract

The effect of coadsorbed CO on potassium surface diffusion on Ru(001) has been studied using coverage grating-optical second harmonic diffraction method. The enhancement of the first-order diffraction peak at 0.06 ML of CO coadsorption coverage demonstrates the very strong electronic interaction between these coadsorbates. At an initial potassium coverage of 1.0 ML, the activation energy for the diffusion of K increases from 2.7 kcal/mol on the clean ruthenium surface to 17.0 kcal/mol in the presence of 0.06 ML CO. At 280 K, the diffusion rate coefficient drops from D ) 6.4 × 10 -10 cm 2 /s on clean ruthenium to D ) 1.5 × 10 -14 cm 2 /s as a result of CO coadsorption. CO and K stabilize each other upon the formation of K y -CO x surface complexes that increase the apparent activation energy for potassium diffusion, thereby slowing its diffusion rate.

Coadsorption of potassium and carbon monoxide on Ni(111): A density functional theory study

“…[1][2][3][4] On the Ni͑111͒ surface, a half coverage of CO forms a c͑2 ϫ 4͒ low-energy electron-diffraction ͑LEED͒ pattern, with molecules adsorbed at both hcp and fcc threefold hollow sites. 5,6 For a coverage of about 0.25 ML, K atoms form an ordered p͑2 ϫ 2͒ structure and occupy the atop sites.…”

Collision-Induced Migration of Adsorbates on Solid Surfaces: An Experimental Approach

“…Finally, the coverage profiles of CO on the modulated potassium density were simulated on the basis of standard LITD equations. − These are shown for demonstration in Figure for initial potassium coverage of 1 ML (before grating formation) and several CO exposures. The final CO coverage was obtained from separate CO sticking measurements on top of various potassium coverages for calibration purposes (these are not shown here).…”

“…Finally, the coverage profiles of CO on the modulated potassium density were simulated on the basis of standard LITD equations. [31][32][33][34][35] These are shown for demonstration in Figure 2 for initial potassium coverage of 1 ML (before grating formation) and several CO exposures. The final CO coverage was obtained from separate CO sticking measurements on top of various potassium coverages for calibration purposes (these are not shown here).…”

First principle study on alkali metals promotion of CO oxidation over Ir(100)

“…Moreover, alkali metals are known as effective promoters in a wide variety of industrial processes, such as the catalytic treatment of automotive exhaust, Fischer–Tropsch reactions, and ammonia synthesis . The deposition of alkali metals on transition metal surfaces is often found to alter their chemical properties and affect their catalytic activity .…”