Crystal orbital contributions to the pyrrhotite valence band with XPS evidence for weak Fe-Fe ? bond formation

Nesbitt, H.W.; Schaufuß, Andrea G; Bancroft, G.M.; Szargan, R.

doi:10.1007/s002690100200

Cited by 16 publications

(8 citation statements)

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“…Recently Nesbitt et al (2002) investigated the valence band structure of hexagonal pyrrhotite (Fe 10 S 11 ) using synchrotron radiation XPS (SXPS) and demonstrated the existence of Fe 3d peak contributions in the upper valence band consistent with the model of Tossell (1977). They also suggested that, due to the similarity of their structure, these contributions should be evident in monoclinic pyrrhotite (Fe 7 S 8 ) and troilite (FeS).…”

Section: Introductionmentioning

confidence: 87%

XPS identification of bulk hole defects and itinerant Fe 3d electrons in natural troilite (FeS)

Skinner

Nesbitt

Pratt

2004

Geochimica et Cosmochimica Acta

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Section: Introductionmentioning

confidence: 87%

XPS identification of bulk hole defects and itinerant Fe 3d electrons in natural troilite (FeS)

Skinner

Nesbitt

Pratt

2004

Geochimica et Cosmochimica Acta

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“…For Fe 2+ in the [FeS 6 ] octahedra with a 3d 6 electron configuration, the energy levels are split into two e g and three t 2g orbitals [15,16]. It is assumed that the overlap between the t 2g orbitals of the interlayer Fe-Fe bonds causes the spin-orbital coupling (SOC), which is responsible for a strong anisotropy with the hard axis in the c-direction and the spin rotation out of the c-plane at T < 200 K [17][18][19]. According to Goodenough [20], the critical value of an Fe-Fe bond length for the overlap of d electrons in NiAs-type monosulfides is 3.0 Å.…”

Section: Introductionmentioning

confidence: 99%

The relation between local structural distortion and the low-temperature magnetic anomaly in Fe₇S₈

Koulialias

Canévet

Charilaou³

et al. 2018

J. Phys.: Condens. Matter

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Structural defects on an atomic level can crucially impact the magnetic properties of a material. We study this phenomenon by means of magnetometry and powder neutron diffraction on a stoichiometric, monoclinic pyrrhotite (FeS), which is a classic omission structure with a magnetic anomaly at about 30 K. The initial structural distortion of the pyrrhotite at 300 K caused by the vacancy arrangement decreases upon cooling, and simultaneous to the magnetic anomaly the anisotropic contraction of the unit cell homogenizes the covalency of the Fe-Fe bonds with lengths less than 3.0 Å and the Fe-S-Fe bond angles. These changes on the atomic level affect the spin-orbit coupling and the super-exchange interactions in FeS, and trigger the low-temperature magnetic anomaly within a crystallographically stable system.

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“…The much stronger peak intensity of Fe 2+ to that of Fe 3+ suggested a larger portion of Fe 2+ in Fe 1– x S. Generally, the valence of Fe was supposed to exhibit the single bivalence to balance the valance of S 2– in stoichiometric FeS. However, the previous reports showed that though the molar ratio of Fe/S was near-stoichiometric in FeS, the defects were still present in the phase at ambient temperature because of the entropic considerations . Moreover, Goodenough pointed out that a very limited deficiency of iron (Fe 1– x S, 0 < x < 0.055) is possible for FeS (troilite) .…”

Section: Resultsmentioning

confidence: 99%

“…However, the previous reports showed that though the molar ratio of Fe/S was near-stoichiometric in FeS, the defects were still present in the phase at ambient temperature because of the entropic considerations. 61 Moreover, Goodenough pointed out that a very limited deficiency of iron (Fe 1−x S, 0 < x < 0.055) is possible for FeS (troilite). 21 Thus, a certain amount of Fe vacancies was supposed to be formed in Fe 1−x S, as the Fe valence has partially varied from +2 to +3.…”

Section: Resultsmentioning

confidence: 99%

Strategic Design of Vacancy-Enriched Fe_1–xS Nanoparticles Anchored on Fe₃C-Encapsulated and N-Doped Carbon Nanotube Hybrids for High-Efficiency Triiodide Reduction in Dye-Sensitized Solar Cells

Chen

Wang²,

Shao

et al. 2018

ACS Appl. Mater. Interfaces

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A new class of hybrids with the unique electrocatalytic nanoarchitecture of FeS anchored on FeC-encapsulated and N-doped carbon nanotubes (FeS/FeC-NCNTs) is innovatively synthesized through a facile one-step carbonization-sulfurization strategy. The efficient synthetic protocols on phase structure evolution and dynamic decomposition behavior enable the production of the FeS/FeC-NCNT hybrid with advanced structural and electronic properties, in which the Fe vacancy-contained FeS showed the 3d metallic state electrons and an electroactive Fe in +2/+3 valence, and the electronic structure of the CNT was effectively modulated by the incorporated FeC and N, with the work function decreased from 4.85 to 4.63 eV. The meticulous structural, electronic, and compositional control unveils the unusual synergetic catalytic properties for the FeS/FeC-NCNT hybrid when developed as counter electrodes (CEs) for dye-sensitized solar cells (DSSCs), in which the FeC- and N-incorporated CNTs with reduced work function and increased charge density provide a highway for electron transport and facilitate the electron migration from FeC-NCNTs to ultrahigh active FeS with the electron-donating effect, and the Fe vacancy-enriched FeS nanoparticles exhibit ultrahigh I adsorption and charge-transfer ability. As a consequence, the DSSC based on the FeS/FeC-NCNT CE delivers a high power conversion efficiency of 8.67% and good long-term stability with a remnant efficiency of 8.00% after 168 h of illumination, superior to those of traditional Pt. Furthermore, the possible catalytic mechanism toward I reduction is creatively proposed based on the structure-activity correlation. In this work, the structure engineering, electronic modulation, and composition control opens up new possibilities in constructing the novel electrocatalytic nanoarchitecture for highly efficient CEs in DSSCs.

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Crystal orbital contributions to the pyrrhotite valence band with XPS evidence for weak Fe-Fe ? bond formation

Cited by 16 publications

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XPS identification of bulk hole defects and itinerant Fe 3d electrons in natural troilite (FeS)

XPS identification of bulk hole defects and itinerant Fe 3d electrons in natural troilite (FeS)

The relation between local structural distortion and the low-temperature magnetic anomaly in Fe₇S₈

Strategic Design of Vacancy-Enriched Fe_1–xS Nanoparticles Anchored on Fe₃C-Encapsulated and N-Doped Carbon Nanotube Hybrids for High-Efficiency Triiodide Reduction in Dye-Sensitized Solar Cells

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Crystal orbital contributions to the pyrrhotite valence band with XPS evidence for weak Fe-Fe ? bond formation

Cited by 16 publications

References 0 publications

XPS identification of bulk hole defects and itinerant Fe 3d electrons in natural troilite (FeS)

XPS identification of bulk hole defects and itinerant Fe 3d electrons in natural troilite (FeS)

The relation between local structural distortion and the low-temperature magnetic anomaly in Fe7S8

Strategic Design of Vacancy-Enriched Fe1–xS Nanoparticles Anchored on Fe3C-Encapsulated and N-Doped Carbon Nanotube Hybrids for High-Efficiency Triiodide Reduction in Dye-Sensitized Solar Cells

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The relation between local structural distortion and the low-temperature magnetic anomaly in Fe₇S₈

Strategic Design of Vacancy-Enriched Fe_1–xS Nanoparticles Anchored on Fe₃C-Encapsulated and N-Doped Carbon Nanotube Hybrids for High-Efficiency Triiodide Reduction in Dye-Sensitized Solar Cells