NO dissociation on rhodium

Sellmer, C.; Schmatloch, V.; Kruse, Norbert

doi:10.1007/bf00807014

Cited by 11 publications

(6 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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.…”

Section: Discussion Summary and Outlookmentioning

confidence: 94%

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

Newton

2009

Top Catal

View full text Add to dashboard Cite

Examples of the application of a synchronous DRIFTS/EXAFS/mass spectrometry (MS) methodology to the study of dilute (B 1wt%) Rh/Al 2 O 3 catalysts are discussed. These are used to explore the potential of this approach for understanding of the behaviour of supported metal catalysts ''in a single shot'', and in the often preferred regime of low (\1 wt%) loadings of active precious metals. Firstly, the sequential interaction of NO (323 K) and then CO (373 K) with reduced, 0.5 wt% Rh/Al 2 O 3 catalysts is studied. Infrared spectroscopy indicates that two surface species (a bent Rh(NO -) and Rh(CO) 2 species) can be created using this sequential gas absorption/reaction method with minimal interference from other carbonyl or nitrosyl species. As such the potential for a reliable structural characterisation of the local structure of these species by EXAFS becomes possible. However, in contrast to the infrared spectroscopy, analysis of the EXAFS data also indicates that, even for such low loaded Rh systems, oxidative disruption of the Rh by the NO and CO is not complete and that bonding typical of small Rh clusters persists in both cases. The possible sources of this apparent spectroscopic difference of opinion are discussed. Secondly, 1wt% Rh/Al 2 O 3 catalysts are studied using dispersive EXAFS at 573 K with 100 ms time resolution, during a redox switching event involving a reducing feedstock comprising just 3000 ppm of CO and 3000 ppm of NO. It is shown that highly useful and insightful time resolved and synchronously obtained XANES/EXAFS/IR data can be obtained even in this dilute Rh and more ''realistic'' case. Additional data, regarding the overall performance of the experiment, as currently implemented at the ESRF, along with a discussion of where enhanced performance might be yet still be gained, are also given.

show abstract

Section: Discussion Summary and Outlookmentioning

confidence: 94%

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

Newton

2009

Top Catal

View full text Add to dashboard Cite

show abstract

“…In addition, nascent cluster ions were constantly supplied to the temperature-controlled extension tube, and thus the resulting TPD curves are given as integrals. 23 The cluster ions were accelerated to a kinetic energy of 3.5 keV in the acceleration region. The ions were detected using a Hamamatsu double-microchannel plate detector, signals of which were amplified with a preamplifier and digitized using an oscilloscope.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

“…Furthermore, the cluster ions remaining after thermal desorption were monitored, and the desorption of neutral species from the cluster ions was not detected. In addition, nascent cluster ions were constantly supplied to the temperature-controlled extension tube, and thus the resulting TPD curves are given as integrals …”

Section: Experimental Sectionmentioning

confidence: 99%

Thermal Desorption and Reaction of NO Adsorbed on Rhodium Cluster Ions Studied by Thermal Desorption Spectroscopy

et al. 2015

View full text Add to dashboard Cite

Cationic rhodium clusters, Rh(n)(+) (n = 4-8), were prepared in the gas phase by the laser ablation of a Rh rod. The Rh(n)(+) clusters were introduced into a reaction gas cell filled with nitric oxide (NO) diluted with He, where they were subjected to collisions with NO and He in a thermal equilibrium at 300 K. The NO molecules were found to adsorb sequentially on the Rh(n)(+) clusters forming Rh(n)(+)(NO)m. To examine the adsorption form and the reaction of NO, we heated Rh(n)(+)(NO)m in an extension tube located after the reaction gas cell and the thermal response of the clusters, desorption of the fragments, was recorded as a function of temperature (300-1000 K). The desorption of NO molecules was predominantly observed below 500 K, giving either Rh(n)(+)(NO)n+1 or Rh(n)(+)(NO)n+2, which indicates that there were NO molecules loosely adsorbed on the Rhn(+) clusters. Further desorption was found to proceed at higher temperatures (500-1000 K), whereby NO was released from the smaller clusters, Rh(n)(+) (n ≤ 5). In contrast, for the larger clusters (n ≥ 6), N2 release was clearly observed at high temperatures (>800 K). Thus, the reduction of NO occurred for larger clusters at higher temperatures.

show abstract

“…Rhodium is a major constituent of the automotive exhaust gas converter, owing to its properties to convert NO to N 2 with high selectivity. 1,2 Adsorption and dissociation of NO has been the subject of studies on polycrystalline Rh [3][4][5][6] and on the three low Miller index surfaces: Rh(111), [7][8][9][10][11][12][13][14][15][16][17][18] Rh(100), [19][20][21][22][23][24][25] and Rh(110). [26][27][28][29][30][31] The results generally indicate that NO adsorbs molecularly at low temperature but dissociates upon heating.…”

Section: Introductionmentioning

confidence: 99%

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

Hopstaken

Niemantsverdriet

2000

J. Phys. Chem. B

View full text Add to dashboard Cite

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).

show abstract

NO dissociation on rhodium

Cited by 11 publications

References 26 publications

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

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

Thermal Desorption and Reaction of NO Adsorbed on Rhodium Cluster Ions Studied by Thermal Desorption Spectroscopy

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

Contact Info

Product

Resources

About