Surface reaction kinetics of NO on Rh{110}

Abstract

The reaction of NO with Rh(110) single crystal surfaces was studied by means of various surface analytical tools including static secondary ion mass spectrometry (SSIMS), temperature programmed desorption (TPD), monochromatized x-ray photoelectron spectroscopy (MXPS), and ion scattering spectroscopy (ISS). Molecular NO adsorption was found to occur below 200 K. Higher temperatures caused dissociation of adsorbed NO molecules. Complete dissociation occurred only below a critical coverage, i.e., ΘNO≤0.12. Nitrogen and oxygen molecules were the only desorption products in TPD under these conditions. For higher coverages, thermal desorption of NO occurred and was found to be associated with an activation energy Ed=130±6 kJ/mol and a preexponential νd=10(15.0±0.8) s−1 for the limit of zero NO coverage in a first order process. The dissociation of molecular NOad caused a shift of the N1s core level binding energies from 400.3 to 397.6 eV. SSIMS studies were performed in either real time or in a temperature programmed manner (TPSSIMS) and the calibrated intensities of ionic species were taken to evaluate the dissociation kinetics. Both the activation energy Edis and the preexponential k0dis for dissociation were determined from the TPSSIMS data by assuming first order kinetics in a Polanyi–Wigner ansatz. Values of Edis=15±2 kJ/mol and k0dis=10(1.9±0.5) s−1 were found. These data are compatible with the rate constant kdis=0.18 s−1 obtained in real-time measurements during the ongoing NO adsorption and dissociation at 300 K. In this case, the SSIMS data were evaluated on the basis of consecutive reaction kinetics, including site inhibition by oxygen and Kisliuk’s precursor-mediated adsorption. ISS measurements indicated that oxygen atoms can also partly diffuse into the interior of the Rh(110) crystal.

Chapter 8 The role of cerium-based oxides used as oxygen storage materials in DeNOx catalysis

“…In fact, it seems that preferential orientation of Rh surface on reduced ceria may also explain the specific role of CeOx surface. This is consistent with the fact that NO dissociation occurs at lower temperatures on Rh (110) and on Rh (100) than on Rh (111) [84,85].…”

Applying Dynamic and Synchronous DRIFTS/EXAFS to the Structural Reactive Behaviour of Dilute (≤1 wt%) Supported Rh/Al2O3 Catalysts using Quick and Energy Dispersive EXAFS

“…At present we might postulate that the reason for the persistence of EXAFS visible Rh-Rh interactions might lie in the results of any dissociative adsorption of the NO [44,45] or subsequently, CO [46][47][48]. The products of any low level dissociation would be invisible to the mid range infrared and yet could quite easily act to curtail oxidative redispersion by adsorbing in high symmetry sites [48]effectively holding Rh atoms together and preventing their dispersion into monodisperse Rh nitrosyl or carbonyl species-or simply blocking the sites from whence oxidative disruption is promoted.…”

Reduction Reaction of Nitric Oxide on the Rh5V+ Cluster: A Density Functional Theory Mechanistic Study

“…As described above, the NO decomposition on the small rhodium clusters is highly effective which was proved in theoretical and experimental studies. − ,− ,,,− However, as is well known, Rh is so expensive and limited in supply, hence there is a continued need to decrease the amount used in the three-way catalytic converters. An effective method is by doping other metals to reduce the amount of precious metal that has been used to improve the catalytic activity. ,− These results indicate that doping other atoms can increase the dissociative adsorption energy.…”

“…The reaction of the adsorption and reduction of NO on rhodium clusters and surfaces has received extensive attention in the areas of surface science. − Size is one of the important parameters influencing the catalytic performance for most catalysts. , For instance, Rh particles have obvious size dependences, and the turnover number decreases gradually with the size decreasing in the reactions of CO + O 2 and CO + NO . The various chemisorption states of NO on Rh(111) and (100) surfaces had been studied with density functional theory (DFT), and the result revealed that the binding energy between NO molecules and Rh surfaces increased with the decrement of the coverages of NO .…”