Reaction between NO and CO on Rh(100): how lateral interactions lead to auto-accelerating kinetics

The reactions between NO and CO adsorbed on Rh(100) were studied with temperature programmed reaction spectrometry and static secondary ion mass spectrometry and compared with similar reactions on Rh(111). Elementary steps in the overall reactions, such as dissociation of NO, and reaction between CO and O atoms were studied as well. Dissociation of NO is faster on the more open Rh(100) surface, while formation of N2 is slower. Desorption of either CO or NO occurs at comparable rates on Rh(100) and Rh(111). The oxidation of CO to CO2 proceeds much faster on Rh(100) than on Rh(111). When the Rh(100) surface is saturated with NO and CO, explosive formation of CO2 is observed, which can be explained by an autocatalytic mechanism, in which the availability of empty sites plays a crucial role

NO dissociatie op Rh(100) : het modelleren van de NO dissociatie op Rh(100) met dynamische Monte Carlo simulaties

No Abstrac

First-principles extrapolation method for accurate CO adsorption energies on metal surfaces

We show that a simple first-principles correction based on the difference between the singlet-triplet CO excitation energy values obtained by DFT and high-level quantum chemistry methods yields accurate CO adsorption properties on a variety of metal surfaces. We demonstrate a linear relationship between the CO adsorption energy and the CO singlet-triplet splitting, similar to the linear dependence of CO adsorption energy on the energy of the CO 2$\pi$* orbital found recently {[Kresse {\em et al.}, Physical Review B {\bf 68}, 073401 (2003)]}. Converged DFT calculations underestimate the CO singlet-triplet excitation energy $\Delta E_{\rm S-T}$, whereas coupled-cluster and CI calculations reproduce the experimental $\Delta E_{\rm S-T}$. The dependence of $E_{\rm chem}$ on $\Delta E_{\rm S-T}$ is used to extrapolate $E_{\rm chem}$ for the top, bridge and hollow sites for the (100) and (111) surfaces of Pt, Rh, Pd and Cu to the values that correspond to the coupled-cluster and CI $\Delta E_{\rm S-T}$ value. The correction reproduces experimental adsorption site preference for all cases and obtains $E_{\rm chem}$ in excellent agreement with experimental results.Comment: Table sent as table1.eps. 3 figure

Elementary Raection kinetic and Lateral Interactions in the catalytic Reaction between No and Co on rhodium Surfaces

+196hlm.;24c

Lateral interactions in the dissociation kinetics of NO on Rh(100)

Temperature programmed desorption and static secondary ion mass spectrometry have been used to study the dissociation and desorption of NO and the formation of N2 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 N2 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 N2 is slower than on Rh(111)

Lateral interactions in the dissociation kinetics of NO on Rh(100)

Temperature programmed desorption and static secondary ion mass spectrometry have been used to study the dissociation and desorption of NO and the formation of N2 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 N2 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 N2 is slower than on Rh(111)