X-ray photoelectron studies of Ca, Sr and Ba and their oxides and carbonates

Sosulnikov, M.I.; Teterin, Yu. A.

doi:10.1016/0368-2048(92)85002-o

Cited by 186 publications

(76 citation statements)

References 14 publications

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“…To identify the origin of the Sr surf we compare the BE of Sr 3d, O 1s, and C 1s features. The values of the Sr 3d, O 1s, and C 1s binding energies (in eV) reported in the literature for different Sr, O, and C containing compounds are summarised in Table 6 [36,57,58,68,69]. The feature at 288.5 eV was clearly observed in the C 1s spectra of the LSC perovskite and LSCC57 composite, thereby implying the possibility of carbonate formation.…”

Section: Surface States Of Co and Sr Cations Carbon And Oxygen Ionsmentioning

confidence: 94%

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Konysheva

Francis

2013

Applied Surface Science

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Keywords:X-ray photoelectron spectroscopy (XPS) Surface composition Composites with perovskite and fluorite structures Oxidation state of cerium cations Binding energy a b s t r a c t X-ray photoelectron spectroscopy (XPS) has been used to explore the cation rearrangement between the surface and bulk of grains and the surface chemical states of Ce, Mn, Co, Sr, and O ions in the single phase CeO 2 -based solid solutions and in the two phase (100 − x)La 0.6 Sr 0.4 CoO 3 -xCeO 2 (LSCCx) and (100 − x)La 0.8 Sr 0.2 MnO 3 -xCeO 2 (LSMCx) composites. The well-resolved Ce 3d 5/2 and Ce 3d 3/2 spin-orbit components were determined to study the Ce 4+ to Ce 3+ electronic transition at the surface. The surface of the LSCCx and LSMCx (x = 8-40 mol%) composites is depleted in cerium. Both Ce 4+ and Ce 3+ cations were revealed. The surface fraction of Ce 4+ cations increases with the rise in CeO 2 content in both systems, but it is higher by about a factor of two in the LSCC composites. A strong enrichment of the surface by Co cations was observed for the composites LSCCx (x = 8-40 mol%), implying that the presence of cerium could facilitate the Co surface segregation. A slight Sr surface enrichment compared to the nominal stoichiometry was found for La 0.6 Sr 0.4 CoO 3 , CeO 2 -based solid solutions, LSCC57, and LSMCx (x = 10-57) composites. In contrast, the surface of the LSCCx (x = 10-37) composites is slightly depleted in strontium cations. The O 1s spectra of the LSCC and LSMC composites contain several contributions associated with the lattice oxygen related to the phases with the perovskite and fluorite structures as well as with different surface states. Their contributions vary with CeO 2 content and a chemical origin of the transition metal cations on the B-site in the perovskite structure. The Ce 2 (CO 3 ) 3 -based phase seems to exist at the surface of grains and crystallites in the LSCC57 and LSCM composites.

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Section: Surface States Of Co and Sr Cations Carbon And Oxygen Ionsmentioning

confidence: 94%

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Konysheva

Francis

2013

Applied Surface Science

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“…In the C 1s region, both COS and Na-COS exhibited two signals at 285.0 eV and 289.6 eV, due to C-H and carbonate groups, respectively [29]. The Ca 2p of COS and Na-COS exhibited a doublet with a separation of 3.5 eV, 2p1/2, and 2p3/2 components, whose binding energy (BE) values were 347.00 eV, 350.5 eV, and 346.3 eV, 349.8 eV, respectively, suggesting that the Ca was associated with CaO [30,31]. In the O 1s spectra, both COS and Na-COS displayed doublet peaks; however, the intensity Figure 3 presented C 1s, Ca 2p, O 1s, and Na 1s regions for COS (bottom) and Na-COS (top).…”

Section: Catalyst Characterizationmentioning

confidence: 99%

Kinetics and Mechanism of NaOH-Impregnated Calcined Oyster Shell-Catalyzed Transesterification of Soybean Oil

et al. 2017

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Abstract:The objective of this research is to develop a kinetic model to describe the transesterification of soybean oil with methanol using NaOH-impregnated calcined oyster shell (Na-COS). Batch experiments were performed via a two-factor randomized complete block design using a molar ratio of methanol to oil (MR) of 6, 12, and 18 and catalyst loadings (CL) (mass of catalyst/mass of oil in %) of 2%, 4%, 6%, and 8% to obtain fatty acid methyl ester yields. In addition, the catalyst was studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion spectrometry (TOF-SIMS) to elucidate the role of the catalyst in the transesterification reaction. XRD and XPS analyses suggested that the formation of sodium peroxide (Na 2 O 2 ) on the surface contributed to catalytic activity. The TOF-SIMS analysis suggested that the transesterification occurred between adsorbed triglyceride and free methanol, similar to the Eley-Rideal mechanism. The transesterification of adsorbed triglyceride to adsorbed diglyceride was found to be the rate-determining step with a rate constant of 0.0059 ± 0.0002 L mol −1 min −1 .

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“…Deconvolution of the O 1s spectra yields three peaks, namely O 1s a (529.0 eV), O 1s b (531.2 eV) and O 1s c (532.9 eV). From the literature, the peak at the 532.9 eV is probably due to the water and hydroxide absorbed on the surface [38][39][40][41], while the peaks at 531.2 eV correspond to carbonate compounds and chemical Adsorption [42][43][44][45][46][47][48][49][50][51]. The main peaks at 529.0 eV (O 1s a) correspond to the oxygen lattice [19,20,50].…”

Section: Xps Studiesmentioning

confidence: 99%

Preparation, surface state and band structure studies of SrTi(1−x)Fe(x)O(3−δ) (x=0–1) perovskite-type nano structure by X-ray and ultraviolet photoelectron spectroscopy

et al. 2012

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X-ray photoelectron studies of Ca, Sr and Ba and their oxides and carbonates

Cited by 186 publications

References 14 publications

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Identification of surface composition and chemical states in composites comprised of phases with fluorite and perovskite structures by X-ray photoelectron spectroscopy

Kinetics and Mechanism of NaOH-Impregnated Calcined Oyster Shell-Catalyzed Transesterification of Soybean Oil

Preparation, surface state and band structure studies of SrTi(1−x)Fe(x)O(3−δ) (x=0–1) perovskite-type nano structure by X-ray and ultraviolet photoelectron spectroscopy

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