Revisiting Diffuse Reflectance Spectroscopy for the Characterization of Metal and Semiconducting Oxide Catalysts

Rakai, A.; Bensalem, Abdelhamid; Müller, Jean-Claude; Tessier, D.; Bozon‐Verduraz, François

doi:10.1016/s0167-2991(08)64556-5

Cited by 11 publications

(4 citation statements)

References 3 publications

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“…The peak at 210 nm corresponds to dispersed Ce 3+ species [2] and the one at 260 nm is due to the 4f-5d interconfiguration transitions of Ce 3+ species [24]. The band at 310 nm has been assigned to CeO 2 [23][24][25] and increases with cerium loading. Therefore, a mixture of cerium species in 3+ and 4+ states coexists in Ce-HMOR and in Ce-Pd-HMOR catalysts.…”

Section: Catalyst Characterizationmentioning

confidence: 95%

“…10 shows the diffuse reflectance UV-VIS spectra of Pd-HMOR during successive reduction and oxidation treatments at temperatures in the range 25-600 • C. During reduction, a band at about 240 nm that grows with temperature is observed. This band has been assigned [23] to the formation of palladium clusters of different sizes at high temperature. No significant changes are observed during the oxidation treatment at different temperatures when compared to the fresh sample at 25 • C. Therefore, it appears that in the fresh catalyst palladium exists in an oxidized state.…”

Section: Catalyst Characterizationmentioning

confidence: 98%

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Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Córdoba

Flytzani‐Stephanopoulos

Correa

2001

Applied Catalysis B: Environmental

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The selective catalytic reduction (SCR) of NO x by dodecane in excess oxygen-containing gas mixtures was studied on Ce and/or Pd-loaded HMOR. Under dry conditions the best fresh bimetallic catalyst, 6.2 wt.% Ce-0.08 wt.% Pd-HMOR, displayed a maximum of about 70% NO x conversion to N 2 at 350 • C and GHSV = 30,000 h −1 , while either Ce-HMOR or Pd-HMOR exhibited low activity for the SCR reaction. The presence of both Ce and Pd in the zeolite was crucial for high deNO x activity. The dodecane concentration is very important for the reaction. The catalyst is not active in the absence of the reducing agent and inhibition of NO x reduction is observed at dodecane concentrations higher than 440-500 ppm. The presence of 40 ppm SO 2 in the gas feed suppresses the reaction. However, the coexistence of 15% H 2 O and 40 ppm SO 2 has no appreciable effect on the catalyst activity. Enhanced activity and a broader temperature window was observed in the NO 2 + dodecane + O 2 reaction in the presence of 15% H 2 O and 100 ppm SO 2 . In this reaction mixture, the catalyst was capable of retaining a stable NO 2 conversion to N 2 for a period of ten days. Characterization by XPS and UV-VIS-diffuse reflectance spectra (UV-VIS-DRS) of selected fresh and aged catalyst samples indicates that Pd exists mainly as Pd 2+ cations in Ce-Pd-HMOR. Cerium is mostly present as CeO 2 on the surface of the zeolite particles. However, part of the cerium in 6Ce-Pd-HMOR, exists as stable Ce 3+ species.

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Section: Catalyst Characterizationmentioning

confidence: 95%

Section: Catalyst Characterizationmentioning

confidence: 98%

Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Córdoba

Flytzani‐Stephanopoulos

Correa

2001

Applied Catalysis B: Environmental

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“…It is important to mention that there is a lot of controversy about this band. According to Rakai et al [79], this band is correlated with a surface redox couple of cerium ions (Ce 3+ /Ce 4+ ). A similar band was found from Bensalem et al [80] and Binet et al [81].…”

Section: Raman Measurementsmentioning

confidence: 99%

Tuning the Catalytic Properties of Copper-Promoted Nanoceria via a Hydrothermal Method

et al. 2019

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Copper-cerium mixed oxide catalysts have gained ground over the years in the field of heterogeneous catalysis and especially in CO oxidation reaction due to their remarkable performance. In this study, a series of highly active, atomically dispersed copper-ceria nanocatalysts were synthesized via appropriate tuning of a novel hydrothermal method. Various physicochemical techniques including electron paramagnetic resonance (EPR) spectroscopy, X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), Raman spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS) were employed in the characterization of the synthesized materials, while all the catalysts were evaluated in the CO oxidation reaction. Moreover, discussion of the employed mechanism during hydrothermal route was provided. The observed catalytic activity in CO oxidation reaction was strongly dependent on the nanostructured morphology, oxygen vacancy concentration, and nature of atomically dispersed Cu2+ clusters.

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“…M n+ in zeolites), (ii) metal-oxygen ''clusters'' at the nanometer scale (d < 10 nm) and (iii) bulk oxide. DRS observations on solid catalysts were reported in the 1990s [48][49][50][51][52][53][54]; for example, according to the particle size, narrow gap semiconductors, such as PdO, are black (large size) or colored (d < 6 nm). DRS gives a significant insight into the characterization of nanoparticles of semiconducting oxides, owing to the intervention of the quantum confinement effect or quantum size effect [46].…”

Section: Complexmentioning

confidence: 99%

UV–Vis–NIRandEPRSpectroscopies

Sojka

Bozon‐Verduraz

Che

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction UV – V is– NIR Spectroscopy EPR Spectroscopy Comparison between UV – V is– NIR ( DRS ) and EPR Spectroscopies Conclusions

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Revisiting Diffuse Reflectance Spectroscopy for the Characterization of Metal and Semiconducting Oxide Catalysts

Cited by 11 publications

References 3 publications

Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Lean NOx reduction with dodecane over cerium and palladium loaded mordenite

Tuning the Catalytic Properties of Copper-Promoted Nanoceria via a Hydrothermal Method

UV–Vis–NIRandEPRSpectroscopies

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