�ber die Lichtabsorption des zweiwertigen Kupfers in oxidischen Phasen

Mont, Otto Schmitz-Du

doi:10.1007/bf00902672

Cited by 6 publications

(3 citation statements)

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“…The enhancement of oscillator strength by temperature because of odd parity vibrationally activated transitions in centrosymmetric Cu 2+ complexes is not observed in glasses (Figure 2), supporting their non‐centrosymmetric nature. In addition, its oscillator strength is an order of magnitude higher than that found in centrosymmetric diluted CuO 6 , as estimated from optical reflectance in MgO: Cu 2+ ( f d‐d ≈10 −5 ) 23. 24 The significant linear temperature dependence of the Cu 2+ oscillator strength in aqueous solution is noteworthy.…”

supporting

confidence: 74%

Zeolitic Imidazolate Framework (ZIF)‐Derived, Hollow‐Core, Nitrogen‐Doped Carbon Nanostructures for Oxygen‐Reduction Reactions in PEFCs

Palaniselvam

Biswal

Banerjee

et al. 2013

Chemistry A European J

148

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The facile synthesis of a porous carbon material that is doped with iron-coordinated nitrogen active sites (FeNC-70) is demonstrated by following an inexpensive synthetic pathway with a zeolitic imidazolate framework (ZIF-70) as a template. To emphasize the possibility of tuning the porosity and surface area of the resulting carbon materials based on the structure of the parent ZIF, two other ZIFs, that is, ZIF-68 and ZIF-69, are also synthesized. The resulting active carbon material that is derived from ZIF-70, that is, FeNC-70, exhibits the highest BET surface area of 262 m(2) g(-1) compared to the active carbon materials that are derived from ZIF-68 and ZIF-69. The HR-TEM images of FeNC-70 show that the carbon particles have a bimodal structure that is composed of a spherical macroscopic pore (about 200 nm) and a mesoporous shell. X-ray photoelectron spectroscopy (XPS) reveals the presence of Fe-N-C moieties, which are the primary active sites for the oxygen-reduction reaction (ORR). Quantitative estimation by using EDAX analysis reveals a nitrogen content of 14.5 wt.%, along with trace amounts of iron (0.1 wt.%), in the active FeNC-70 catalyst. This active porous carbon material, which is enriched with Fe-N-C moieties, reduces the oxygen molecule with an onset potential at 0.80 V versus NHE through a pathway that involves 3.3-3.8 e(-) under acidic conditions, which is much closer to the favored 4 e(-) pathway for the ORR. The onset potential of FeNC-70 is significantly higher than those of its counterparts (FeNC-68 and FeNC-69) and of other reported systems. The FeNC-based systems also exhibit much-higher tolerance towards MeOH oxidation and electrochemical stability during an accelerated durability test (ADT). Electrochemical analysis and structural characterizations predict that the active sites for the ORR are most likely to be the in situ generated N-FeN(2+2)/C moieties, which are distributed along the carbon framework.

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confidence: 74%

Zeolitic Imidazolate Framework (ZIF)‐Derived, Hollow‐Core, Nitrogen‐Doped Carbon Nanostructures for Oxygen‐Reduction Reactions in PEFCs

Palaniselvam

Biswal

Banerjee

et al. 2013

Chemistry A European J

148

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“…The optical spectrum of 5% Cu(II) doped MgO have been previously reported and broadband transitions were observed with maxima at 5500 cm −1 and 11 500 cm −1 . These have been assigned to the vertical transitions between the two surfaces of the E g state and the E g → T 2g transition, respectively .…”

Section: Discussionmentioning

confidence: 69%

“…These have been assigned to the vertical transitions between the two surfaces of the E g state and the E g → T 2g transition, respectively . There is some uncertainty, however, in the nature of the lower energy transition . For strong E g ⊗e g Jahn−Teller coupling, with the neglect of second order coupling and any Jahn−Teller effects in the T 2g state, the energies of these Franck−Condon maxima are 4 E JT and Δ o + 2 E JT , respectively, from which one obtains: E JT = 1375 cm −1 and Δ o = 8750 cm −1 .…”

Section: Discussionmentioning

confidence: 99%

The Jahn−Teller Effect in Cu(II) Doped MgO

et al. 2008

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The Cu(II) doped MgO system is known to display features indicating behavior intermediate between static and dynamic Jahn-Teller effects at low temperature. The system is interesting as there is a low barrier between equivalent Jahn-Teller distortions in the cubic host lattice. In order to study the geometry of the Cu(II) ion in this system, we have recorded the low temperature magnetic circular dichroism (MCD) and X-ray absorption fine structure (XAFS) spectra. The spectra have been interpreted in terms of the Cu(II) centers distorting the host lattice such that the CuO 6 center is a tetragonally elongated octahedron.

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