Lateral Interactions in the Dissociation Kinetics of NO on Rh(100)

Abstract

Temperature programmed desorption and static secondary ion mass spectrometry have been used to study the dissociation and desorption of NO and the formation of N 2 on the (100) surface of rhodium. At low coverages we find an activation energy of 37 ( 5 kJ/mol for dissociation of NO and 225 ( 5 kJ/mol for N 2 desorption. At higher coverages the dissociation is significantly retarded by lateral interactions with N-and O-atoms and NO molecules. At coverages close to saturation the dissociation is entirely blocked by NO due to the lack of ensembles containing empty sites. The results are compared with those of earlier studies on Rh(111). It appears that dissociation of NO proceeds faster on the more open Rh(100) surface, due to the higher heat of adsorption of the N-atoms. As a consequence, formation of N 2 is slower than on Rh(111).

Structure sensitivity in the CO oxidation on rhodium: Effect of adsorbate coverages on oxidation kinetics on Rh(100) and Rh(111)

“…37 The Rh͑111͒ crystal surface was cleaned in a similar fashion at slightly higher temperatures, as described previously. 13 After the cleaning procedure, residual oxygen was removed and surface order was restored by annealing the crystals to 1400 K. Surface cleanliness and ordering were checked by Auger spectroscopy, which did not show any contamination and LEED, which showed sharp p(1ϫ1) patterns for both crystals.…”

Spectroscopic Link between Adsorption Site Occupation and Local Surface Chemical Reactivity

“…This quantity is important to understand the NO reduction process in the automotive threeway catalyst [26]. The results are plotted in Fig.…”

Quantification of lateral repulsion between coadsorbed CO and N on Rh(100) using temperature-programmed desorption, low-energy electron diffraction, and Monte Carlo simulations

“…2. The rhodium crystal of ͑100͒ orientation has a thickness of about 1.2 mm and was mounted on a moveable sample rod by two tantalum wires of 0.3 mm diameter, pressed into small grooves on the side of the crystal.…”

“…1,2 Therefore, quantitative information about lateral interactions is essential to model reaction kinetics correctly at high coverages, as met under realistic catalytic conditions. Obviously, single-crystal adsorption calorimetry ͑SCAC͒ is the most direct way to determine lateral interactions in a quantitative fashion.…”

“…We focus on the system COϩNO on Rh͑100͒, which is of interest for automotive exhaust catalysis 5,6 and for which a number of elementary kinetic parameters have recently been obtained. 2,7,8 The reason for selecting Rh͑100͒ instead of ͑111͒ is that the chemistry on the latter may be dominated by defects, whereas reactions on Rh͑100͒ are expected to reflect intrinsic chemistry of the ͑100͒ surface, as was observed for the elementary reaction COϩO to CO 2 . 8 To the best of our knowledge, there is hardly any quantitative information available on interactions between CO and coadsorbates on rhodium.…”