X-ray photoelectron spectroscopy, X-ray auger electron spectroscopy and electron spin resonance studies of the reduction of some solid metal 12-molybdophosphates

Akimoto, Masamichi; Shima, Kenji; Echigoya, Etsuro

doi:10.1039/f19837902467

Cited by 13 publications

(2 citation statements)

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“…The XP spectra of the samples showed three O 1s peaks at 531.2 eV, 532.6 eV, and 534.1 eV, respectively. The peak at 531.2 eV could be assigned to W-O-W or Mo-O-Mo species [29]. The peak at 532.6 eV is attributed to W-O-P or Mo-O-P species.…”

Section: Resultsmentioning

confidence: 95%

Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

2019

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La-exchanged 12-tungstophosphoric acid (La x TPA) and 12-molybdophosphoric acid (La x MPA) salts (x = 0.25, 0.50, 0.75 and 1.00) were prepared via an ion exchange method. The physico-chemical characteristics of the materials were analyzed by using elemental analysis, X-ray diffraction (XRD), Fourier transformed infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), N 2 -physical adsorption, X-ray photoelectron spectroscopy (XPS), and acidity-basicity measurements. The results indicated that La was introduced into the secondary structure of heteropolyacid (HPA) and have not influenced the primary structure, which effectively improved the surface area and pore size. Acidity-basicity studies indicated that incorporation of La resulted in a decrease in the number of acid sites and an increase in the number of basic sites. The catalytic activity of samples was studied in transesterification of glyceryl tributyrate with methanol and La x TPA samples which exhibited high activity compared to La x MPA samples due to having more active basic sites and a larger surface area. Calcined La x TPA samples showed excellent stability, outstanding recyclability, and high activity for one pot transesterification and esterification processes. This outcome was attributed to the presence of balanced acidic and basic sites.

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Section: Resultsmentioning

confidence: 95%

Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

2019

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“…This new ERS-HPA will be called heteropoly-green-blue ERS. This particular structure type presents irreversible reduction with appreciated structural changes 33 in comparison with the heteropoly-blue compounds. 2 In order to investigate the electrodeposition of ERS-HPA on top of a surface other than HOPG, a fresh solution of HPA was injected into the fluid cell.…”

Section: Resultsmentioning

confidence: 96%

In Situ Atomic Force Microscopy Imaging of a Heteropolyanion onto a HOPG Electrode during Its Cyclic Voltammetry

Rivera¹,

Holguin²,

Moreno³

et al. 2002

J. Electrochem. Soc.

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The voltammetric electrodeposition of the heteropolyanion ͑HPA͒ ͓CoMo 6 O 18 (OH) 6 ͔ 3Ϫ on the surface of highly oriented pyrolytic graphite ͑HOPG͒ was studied by in situ atomic force microscopy ͑AFM͒. The electrochemical behavior of the HPA showed voltammetric plots similar to those found on the growth mechanism of organic conducting polymers. The combined electrochemical behavior and the AFM images revealed that electroreduced species of HPA ͑ranging from Ϫ1.5 to 0.6 V vs. Ag wire͒ were deposited on the graphite surface in an irregular aggregation. The depth and morphology of the deposit changed as the number of potential cycles and concentration were modified. Additionally, the electrodeposits were characterized by scanning electron microscopy-energy dispersive spectroscopy techniques. These results show that electrochemical studies of inorganic compounds by electrochemistry-AFM provide a strong evidence of electrodeposition for heteropolyanions such as the HPA molecule.Over the last few years, the importance of heteropolyoxometalates ͑HPOM͒ has increased considerably since they can be used in modified electrodes. 1 These compounds are multielectronic oxidizers, which present a strong blue color ͑''heteropolyblues''͒ when they are reduced and become mixed-valence compounds. 2 For these reasons, HPOM can be used in homo-and heterocatalysts, 3,4 solar energy sources, 5 electrochromic materials, 6 and more recently, medical applications. 7 Electrochemical studies on HPOM reveal they transfer up to 8 electrons in four steps. 8 In a recent report, the application of HPOM in modified electrodes shows that these compounds can form monolayer and multilayer structures on electrode surfaces. 9 On the other hand, it is well known that scanning probe microscopes ͑SPM͒ are important tools in surface science because they are capable to characterize surface structures with molecular resolution at different interfaces. It has been shown that scanning tunneling microscopy ͑STM͒ and atomic force microscopy ͑AFM͒ provide a better understanding on interfacial phenomena since they can investigate interfacial processes in situ at the local scale. Now the application of these techniques to study the structure and reactivity of solutions on electrode surfaces includes a rich variety of materials. 10 In particular, materials such as inorganic adsorbates like polyoxometalates, which have industrial and medical applications, have been investigated with these techniques. 11,12 STM has been used to study successfully the deposition on highly-ordered pyrolytic graphite ͑HOPG͒ of different HPOM by evaporative adsorption and electrochemical deposition. [13][14][15][16][17][18] Resulting STM images showed, in both cases, ordered domains after few voltammetric cycles; unfortunately, the interpretation of these images remains unclear. 13,14 On the other hand, although electrochemical deposition of metals and organic molecules onto several substrates have been reported extensively, 19,20 little work has been done to characterize the electrochem...

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ChemInform Abstract: X‐RAY PHOTOELECTRON SPECTROSCOPY, X‐RAY AUGER ELECTRON SPECTROSCOPY, AND ELECTRON SPIN RESONANCE STUDIES OF THE REDUCTION OF SOME SOLID METAL 12‐MOLYBDOPHOSPHATES

Akimoto¹,

Shima²,

Echigoya³

1983

Chemischer Informationsdienst

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X-ray photoelectron spectroscopy, X-ray auger electron spectroscopy and electron spin resonance studies of the reduction of some solid metal 12-molybdophosphates

Cited by 13 publications

References 0 publications

Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

Lanthanum Exchanged Keggin Structured Heteropoly Compounds for Biodiesel Production

In Situ Atomic Force Microscopy Imaging of a Heteropolyanion onto a HOPG Electrode during Its Cyclic Voltammetry

ChemInform Abstract: X‐RAY PHOTOELECTRON SPECTROSCOPY, X‐RAY AUGER ELECTRON SPECTROSCOPY, AND ELECTRON SPIN RESONANCE STUDIES OF THE REDUCTION OF SOME SOLID METAL 12‐MOLYBDOPHOSPHATES

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