Correlation between the chromaticity, dielectric properties and structure of the binary metal pyrophosphates, Cu(2−x)ZnxP2O7

Baitahe, Rattanai; Vittayakorn, Naratip; Maensiri, Santi

doi:10.1039/c5ra11103j

Cited by 11 publications

(6 citation statements)

References 38 publications

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“…In particular, the presence of the postedge shoulder and the absence of the rising-edge shoulder can indicate visual agreement between the XANES of PC5 and Cu (pyro)phosphates. The FT EXAFS of PC5 is in general agreement with both Cu phosphate and Cu pyrophosphate at radial distances below 3 Å. However, PC5 is more similar to Cu 2 P 2 O 7 than to Cu 3 (PO 4 ) 2 at higher radial distances. , The absence of a complete agreement is associated with differences in the Cu local coordination between the bulk and nanosized compounds.…”

Section: Discussionmentioning

confidence: 63%

“…However, PC5 is more similar to Cu 2 P 2 O 7 than to Cu 3 (PO 4 ) 2 at higher radial distances. 85,87 The absence of a complete agreement is associated with differences in the Cu local coordination between the bulk and nanosized compounds. Moreover, pure spectra derived from MCR-ALS analysis cannot be accurately represented by standard compounds.…”

Section: Discussionmentioning

confidence: 99%

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Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

et al. 2022

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Biodiesel is a promising renewable fuel, which may help to limit our dependence on fossil fuels. However, the presence of contaminants in biodiesel can affect the Cu speciation of the Cu-SSZ-13 selective catalytic reduction (SCR) catalyst, resulting in its deactivation and decreased durability. In situ Cu K-edge X-ray absorption fine structure (XAFS) scanning during a temperature-programmed reduction in hydrogen (H2-TPR) has been applied here for the analysis of Cu speciation in Cu-SSZ-13 catalysts aged using pure and contaminated biodiesel fuels. XAFS data were analyzed using the multivariate curve resolution alternating least-squares (MCR-ALS) method. While only reduction from CuII to CuI was observed at temperatures below 500 °C for the catalyst aged using pure biodiesel, a one-step reduction of CuII to Cu0 at temperatures between 400 and 500 °C was found for the catalyst aged using P-doped biodiesel. The transformation of isolated CuII species to CuII clusters was suggested for the catalyst as a result of aging using P-doped biodiesel. The catalyst aged using S-doped biodiesel showed mainly the reduction of isolated CuII to CuI, which was inhibited as compared to that observed for the catalyst aged using pure biodiesel. The reduction of the catalyst aged using P+S-doped biodiesel led to the reduction of CuII to both CuI and Cu0. The phosphorus was responsible for the formation of CuII clusters during aging of the catalyst using P+S-doped biodiesel. This study reveals that the presence of phosphorus in biofuels should be strictly regulated to avoid major changes in the Cu speciation of Cu-SSZ-13 catalysts.

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Section: Discussionmentioning

confidence: 63%

Section: Discussionmentioning

confidence: 99%

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

et al. 2022

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“…Even more problematic turned out to be the analysis of the copper vibrations. Here, the Cu-O stretching motions, according to the theory, ought to appear in the form of the bands centered in-between 100 and 300cm −1 [54]. The strongest PDOS signal indicates the greatest contribution of Cu vibrations below 200cm −1 .…”

Section: Raman Scatteringmentioning

confidence: 89%

Ab initio studies for characterization and identification of nanocrystalline copper pyrophosphate confined in mesoporous silica

Pastukh¹,

Laskowska²,

Dulski³

et al. 2021

Nanotechnology

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Here we employ a novel method for preparing the homogeneous copper pyrophosphate nanocrystals inside silica mesopores. In order to characterize and identify synthesized nanocrystals we performed the ab initio studies of the α phase of Cu2P2O7. The electronic and crystal structure were optimized within the density functional theory with the strong electron interactions in the states on copper atoms and van der Waals corrections included in calculations. The relaxed lattice parameters and atomic positions agree very well with the results of the diffraction measurements for nanocrystalline copper pyrophosphates embedded inside SBA-15 silica pores. The obtained Mott insulating state with the energy gap of 3.17 eV exhibits the antiferromagnetic order with magnetic moments on copper atoms (0.8 ) that is compatible with the experimental studies. The phonon dispersion relations were obtained to study the dynamical properties of the Cu2P2O7 lattice and the element-specific atomic vibrations were analyzed using the partial phonon density of states. The calculated Raman spectrum revealed the consistency of typical bands of Cu2P2O7 with the experimental data. The investigation that combines a new synthesis of nanomaterials with the first-principles calculations is important for better characterization and understanding of the physical properties relevant for nanotechnological applications.

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“…These nanoparticle sizes are in reasonable agreement with the grain sizes (d = 43 and 46 nm for Cu 2 P 2 O 7 −OAc and −NO 3 , respectively) calculated from the (002) diffraction lines using Scherrer's equation (Table 1). The FTIR spectra of both Cu 54,55 The Cu K-edge X-ray absorption near-edge structure (XANES) and the Cu K-edge extended X-ray absorption fine structure (EXAFS) oscillations were acquired for each Cu 2 P 2 O 7 and copper oxide sample (Figure S9c,d). The XANES spectrum of Cu 2 P 2 O 7 shows a pre-edge of Cu 2+ at 8977 eV, which is assignable to the 1s → 3d transition, 56 similar to the pre-edge of Cu 2+ observed in the spectrum of CuO.…”

Section: Catalyst Effect Of Metal Phosphate On Ch 4 Oxidation Into Hchomentioning

confidence: 99%

Copper Phosphate Nanostructures as Catalysts for the Direct Methane Oxidation

Matsuda,

Aihara,

Kiyohara

et al. 2024

ACS Appl. Nano Mater.

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The development of heterogeneous catalysts for the selective direct transformation of methane (CH 4 ) remains a challenge because of the difficulty in activating the strong C−H bond and controlling selectivity to target products. The effect of various metal phosphate catalysts (37 examples) on the direct oxidation of CH 4 to formaldehyde (HCHO) with molecular oxygen (O 2 ) as the sole oxidant was studied using a fixed-bed flow reactor, and the effectiveness of the copper phosphate catalysts was confirmed. Four crystalline copper phosphates (Cu 2 P 2 O 7 , Cu 3 (PO 4 ) 2 , Cu 2 (P 4 O 12 ), and Cu 4 O(PO 4 ) 2 ) with different Cu coordination geometries and Cu/P ratios were synthesized from Cu(OAc) 2 •H 2 O and (NH 4 ) 2 HPO 4 , and the dependence of CH 4 oxidation on their structures, as well as that on the structure of CuO, was investigated. The Cu/P molar ratio strongly affected the oxidation catalysis; CH 4 conversion increased with increasing Cu/P molar ratio, although the selectivity to HCHO decreased. Among the investigated Cu-based catalysts and metal phosphate nanoparticles (FePO 4 and BiPO 4 ), monoclinic Cu 2 P 2 O 7 , which has a Cu/P ratio of 1/1, exhibited the highest HCHO yield. The catalytic activity of Cu 2 P 2 O 7 was improved by changing the copper source to Cu(NO 3 ) 2 •3H 2 O due to the surface nanostructure control. On the basis of mechanistic studies that include catalyst effect, kinetics, isotope-labeling, and pulse reaction experiments, as well as infrared spectroscopic analyses of adsorbed probe molecules, (i) surface lattice oxygen species of Cu 2 P 2 O 7 possibly react with CH 4 to give HCHO as the primary product and (ii) the surface redox-active Lewis acidic Cu 2+ sites and weakly basic phosphate units on Cu 2 P 2 O 7 play important roles in the C−H activation and the suppression of overoxidation to CO 2 , respectively. Density functional theory calculations revealed that the vacancy formation energies at oxygen sites in β-Cu 2 P 2 O 7 , which was formed by the phase transition of α-Cu 2 P 2 O 7 under the catalytic conditions, were lower than those in α-Cu 2 P 2 O 7 . Such a superior oxygen-transfer ability likely contributes to the high catalytic performance and durability of Cu 2 P 2 O 7 for the oxidation of CH 4 to HCHO.

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Correlation between the chromaticity, dielectric properties and structure of the binary metal pyrophosphates, Cu_(2−x)Zn_xP₂O₇

Abstract: The phenomena of both dielectric and optical properties of binary metal pyrophosphates resulted from the changing crystal structure of the respective P2O74− cluster and octahedral MO6 site.

Cited by 11 publications

References 38 publications

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

Ab initio studies for characterization and identification of nanocrystalline copper pyrophosphate confined in mesoporous silica

Copper Phosphate Nanostructures as Catalysts for the Direct Methane Oxidation

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Correlation between the chromaticity, dielectric properties and structure of the binary metal pyrophosphates, Cu(2−x)ZnxP2O7

Abstract: The phenomena of both dielectric and optical properties of binary metal pyrophosphates resulted from the changing crystal structure of the respective P2O74− cluster and octahedral MO6 site.

Cited by 11 publications

References 38 publications

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H2-TPR

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H2-TPR

Ab initio studies for characterization and identification of nanocrystalline copper pyrophosphate confined in mesoporous silica

Copper Phosphate Nanostructures as Catalysts for the Direct Methane Oxidation

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Correlation between the chromaticity, dielectric properties and structure of the binary metal pyrophosphates, Cu_(2−x)Zn_xP₂O₇

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR

Impact of Biodiesel-Based Phosphorus and Sulfur on Copper Speciation of Cu-SSZ-13 Catalysts: XAFS Scanning during H₂-TPR