N 1s orbital binding energies of some pyrazole pyrazoline compounds by XPS

Katrib, A.; El‐Rayyes, N. R.; Al‐Kharafi, F. M.

doi:10.1016/0368-2048(83)85079-8

Cited by 23 publications

(16 citation statements)

References 4 publications

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“…The two major components at 399.3 eV and 400.8 eV are consistent with a pyrazole-like moiety whereas the minor peak at 402.7 eV is attributed to a quaternary-like nitrogen. 15,55 Similar results were obtained from analysis of the heat-treated NGO sample (Fig. S4 †).…”

Section: Resultssupporting

confidence: 77%

CO tolerance of Pt and PtSn intermetallic electrocatalysts on synthetically modified reduced graphene oxide supports

et al. 2015

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Pt and PtSn intermetallic nanoparticle (NP) catalysts were grown directly on various reduced graphene oxide (rGO) supports and were characterized by a combination of X-ray photoelectron spectroscopic (XPS), Raman microscopy, transmission electron microscopy (TEM), and powder X-ray diffraction (XRD) studies. Electrochemical CO stripping and rotating disk electrochemical (RDE) experiments showed the four rGO-PtSn catalysts to be superior to the four rGO-Pt catalysts for CO and CO-H2 electrooxidation in acidic solutions regardless of the rGO support, in agreement with earlier reports on PtSn NP electrocatalysts. For the four rGO-Pt catalysts, the rGO support causes a 70 mV spread in CO oxidation peak potential (ΔEpeak) and a 200 mV spread in CO-H2 electrooxidation onset. The more oxygenated graphenes show the lowest CO oxidation potentials and the best CO tolerance. For the four rGO-PtSn intermetallic catalysts, a ∼160 mV spread in CO-H2 electrooxidation onset is observed. With the exception of the nitrogen-doped graphene (NGO), a similar trend in enhanced CO electrooxidation properties with increasing oxygen content in the rGO support is observed. The NGO-PtSn electrocatalyst was superior to the other rGO-PtSn catalysts and showed the largest improvement in CO tolerance relative to the pure Pt system. The origin of this enhancement appears to stem from the unique rGO-PtSn support interaction in this system. These results are discussed in the context of recent theoretical and experimental studies in the literature.

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Section: Resultssupporting

confidence: 77%

CO tolerance of Pt and PtSn intermetallic electrocatalysts on synthetically modified reduced graphene oxide supports

et al. 2015

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“…11,44,45 The lower-energy peak can be attributed to the two-coordinate (pyridine-like) nitrogen atom, whereas the ca. 400 eV peak can be attributed to the three-coordinate (pyrrole-like) nitrogen atom.…”

Section: Resultsmentioning

confidence: 98%

Near-edge x-ray absorption fine structure spectroscopy study of nitrogen incorporation in chemically reduced graphene oxide

Dennis¹,

Schultz²,

Jaye³

et al. 2013

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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The chemical reduction of exfoliated graphene oxide (GO) has gained widespread acceptance as a scalable route for the preparation of chemically derived graphene albeit with remnant topological defects and residual functional groups that preclude realization of the conductance of single-layered graphene. Reduction of GO with hydrazine is substantially effective in restoring the π-conjugated framework of graphene and leads to about a five-to-six orders of magnitude decrease of sheet resistance, but has also been found to result in incidental nitrogen incorporation. Here, the authors use a combination of x-ray photoelectron spectroscopy (XPS) and C, O, and N K-edge near-edge x-ray absorption fine structure (NEXAFS) spectroscopy to examine the local geometric and electronic structure of the incorporated nitrogen species. Both NEXAFS and XPS data suggest substantial recovery of the sp2-hybridized graphene framework upon chemical reduction and removal of epoxide, ketone, hydroxyl, and carboxylic acid species. Two distinct types of nitrogen atoms with pyridinic and pyrrolic character are identified in reduced graphene oxide. The N K-edge NEXAFS spectra suggest that the nitrogen atoms are stabilized within aromatic heterocycles such as pyrazole rings, which has been further corroborated by comparison to standards. The pyrazole fragments are thought to be stabilized by reaction of diketo groups on the edges of graphene sheets with hydrazine. The incorporation of nitrogen within reduced graphene oxide thus leads to local bonding configurations very distinct from substitutional doping observed for graphene grown by chemical vapor deposition in the presence of NH3.

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“…72−74 The observation of a single N 1s XPS signal is inconsistent with the presence of notable amounts of pyrazole for which distinct sp 2 and sp 3 nitrogen signals separated by 1.3−1.8 eV would be expected, unlike the single peaks characteristic of metal-bound pyrazolates. 75,76 If reduction to form a free pyrazoline had occurred in the presence of H 2 , one symmetrical signal around ∼400 eV would be expected, but such an assignment was considered unlikely due to the significantly lower binding energy of 398.8 eV observed upon reduction of 1 in the presence of H 2 (Figure S21b). 75 Interestingly, when the Guerbet reaction of 1-butanol promoted by 10 mol % NaOBu was carried out under an atmosphere of N 2 , a TOF of 20 956 Ru −1 h −1 (Table S16) was observed for 1 (versus TOF = 17 416 Ru −1 h −1 for the equivalent reaction carried out under air (Table S4, entry 1)).…”

Section: ■ Effect Of Ruthenium Ligandmentioning

confidence: 99%

Structural Evolution of MOF-Derived RuCo, A General Catalyst for the Guerbet Reaction

Neumann

Payne

Rozeveld

et al. 2021

ACS Appl. Mater. Interfaces

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Guerbet alcohols, a class of β-branched terminal alcohols, find widespread application because of their low melting points and excellent fluidity. Because of the limitations in the activity and selectivity of existing Guerbet catalysts, Guerbet alcohols are not currently produced via the Guerbet reaction but via hydroformylation of oil-derived alkenes followed by aldol condensation. In pursuit of a one-step synthesis of Guerbet alcohols from simple linear alcohol precursors, we show that MOF-derived RuCo alloys achieve over a million turnovers in the Guerbet reaction of 1-propanol, 1-butanol, and 1-pentanol. The active catalyst is formed in situ from ruthenium-impregnated metal–organic framework MFU-1. XPS and XAS studies indicate that the precatalyst is composed of Ru precursor trapped inside the MOF pores with no change in the oxidation state or coordination environment of Ru upon MOF incorporation. The significantly higher reactivity of Ru-impregnated MOF versus a physical mixture of Ru precursor and MOF suggests that the MOF plays an important role in templating the formation of the active catalyst and/or its stabilization. XPS reveals partial reduction of both ruthenium and MOF-derived cobalt under the Guerbet reaction conditions, and TEM/EDX imaging shows that Ru is decorated on the edges of dense nanoparticles, as well as thin nanoplates of CoO x . The use of ethanol rather than higher alcohols as a substrate results in lower turnover frequencies, and RuCo recovered from ethanol upgrading lacks nanostructures with plate-like morphology and does not exhibit Ru-enrichment on the surface and edge sites. Notably, 1H and 31P NMR studies show that through use of K3PO4 as a base promoter in the RuCo-catalyzed alcohol upgrading, the formation of carboxylate salts, a common side product in the Guerbet reaction, was effectively eliminated.

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N 1s orbital binding energies of some pyrazole pyrazoline compounds by XPS

Cited by 23 publications

References 4 publications

CO tolerance of Pt and PtSn intermetallic electrocatalysts on synthetically modified reduced graphene oxide supports

CO tolerance of Pt and PtSn intermetallic electrocatalysts on synthetically modified reduced graphene oxide supports

Near-edge x-ray absorption fine structure spectroscopy study of nitrogen incorporation in chemically reduced graphene oxide

Structural Evolution of MOF-Derived RuCo, A General Catalyst for the Guerbet Reaction

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