Electronic Structure Of Cobalt Research Articles

Composition-dependent PMS activation in SrxLa2-xCoO4±δ perovskite-derivatives: From radical to strengthen the electron-transfer pathway

Ruddlesden-Popper phases (R-P) with the chemical formula SrxLa2-xCoO4±δ (x=0.6, 0.8, 1.0, 1.2, and 1.5), consisting of alternating layers of perovskite and rock-salt type oxides, were found to be efficient catalysts for peroxymonosulfate (PMS) activation. By modifying the strontium content, it is possible to tune the spin state of cobalt in the material, which in turn affects the PMS activation mechanism. When the rock-salt layer is intercalated in the R-P perovskite structure, as in Sr0.8La1.2CoO4, a non-radical pathway is involved, which exhibits superior performance in PMS activation, as indicated by the higher reaction rate constant (0.70 min−1) compared to LaCoO3 (0.13 min−1) with SO4•- generation as the primary mechanism. This research provides a deeper understanding of how the electronic structure of cobalt in perovskite oxides influences the PMS activation mechanism. Such insights are crucial for the rational design of effective PMS activators for water treatment.

Electronic Structure of Aqueous [Co(bpy)3]2+/3+ Electron Mediators.

We report on the electronic structure of cobalt(II) tris-2,2'-bipyridine and cobalt(III) tris-2,2'-bipyridine in aqueous solution using resonant inelastic X-ray scattering (RIXS) spectroscopy at the Co L-edge and N K-edge resonances. Partial fluorescence yield X-ray absorption spectra at both edges were obtained by signal integration of the respective RIXS spectra. Experiments are complemented by calculations of the X-ray absorption spectra for high- and low-spin configurations using density functional theory/restricted open-shell configuration interaction singles and time-dependent density functional theory methods. We find that linear combinations of the simulated X-ray absorption spectra for different spin states reproduce the experimental spectra. Best agreement is obtained for measurements at the Co L-edge, for both samples. For cobalt(II) tris-2,2'-bipyridine, our combined experimental and computational study reveals ∼40% low-spin and ∼60% high-spin state components. Much stronger low-spin character is found for cobalt(III) tris-2,2'-bipyridine, ∼80% low spin and ∼20% high spin. Prominent energy-loss features in the Co RIXS spectra are indicative of d-d excitations and charge-transfer excitations due to strong mixing between metal and ligand orbitals in both complexes. Analysis of N 1s RIXS data reveals the emission from metal dominated orbitals in the valence region, supporting the strong metal-ligand mixing.

Specific features of the formation of atomic magnetic moments in amorphous films RE-Co (RE = La, Gd, Tb)

A systematic investigation of the magnetic properties of amorphous films in (RE) x Co100 − x binary systems in the ground state with rare-earth elements (RE) of different types has been performed. The concentration dependences of the average atomic magnetic moments of cobalt (m Co), gadolinium (m Gd), and terbium (m Tb) have been determined from the analysis of the spontaneous magnetization of the films with a nonmagnetic rare-earth element (La), a rare-earth element with a spherical electron shell (Gd), and a rareearth element with a large orbital magnetic moment (Tb). It has been shown that, in the range 0 < x < 50 at %, the magnetic moment m Co decreases from 1.7 μB to zero, the magnetic moment m Gd remains unchanged and almost coincides with the magnetic moment of the free atom (7 μB), and the value of m Tb decreases monotonically, but the rate of decrease depends on the method of the sample preparation. The revealed regularities are associated with the concentration change in the electronic structure of cobalt and with the specificity of the magnetic structure of the films, which has a ferromagnetic, ferrimagnetic, or sperimagnetic character for samples containing La, Gd, or Tb, respectively.

The electronic structure of cobalt(II) phthalocyanine adsorbed on Ag(111)

The electronic states of submonolayers and multilayers of cobalt(II) phthalocyanine (CoPc) adsorbed on Ag(111) were examined with photoelectron spectroscopy to obtain insight into the details of the substrate–adsorbate interaction. UV photoelectron spectroscopy (UPS) reveals the presence of two interaction-related valence states in the direct vicinity of the Fermi edge, in agreement with previous DFT calculations. X-ray photoelectron spectra indicate that the substrate–adsorbate interaction results in transfer of electron density from the substrate to the Co(II) ion. Substantial changes in the Co 2p multiplet structure, a spectral pattern induced by the open-shell character of the central Co(II) ion, indicate a complete quenching of the molecular spin. While pristine CoPc molecules are paramagnetic with S=1/2, molecules in direct contact to the Ag(111) substrate appear to be in a diamagnetic state.

Effect of Se in Co-based selenides towards oxygen reduction electrocatalytic activity

In this study, Co-based selenides with various selenium contents have been synthesized by heating dodecacarbonyltetracobalt [Co4(CO)12] and elemental selenium in 1,6-hexanediol solvent under refluxing conditions. The synthesized catalyst powders are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The samples exhibit cauliflower-like surface morphologies and reveal the crystalline characteristics of orthorhombic CoSe2 compound. Electrocatalytic performances of the Co–Se compounds for the oxygen reduction reaction in 0.5M H2SO4 electrolyte are evaluated by rotating disk electrode (RDE). Co–Se catalysts are electrochemical stable in the potential range of 0.05–0.80V (vs. NHE). The catalytic activity changes with increasing selenium content, and the highest activity is obtained at 67.1mol% Se in the catalyst, which can be attributed to the modification of selenium element on the electronic structure of cobalt.

Magnetic Circular Dichroism Spectroscopy as a Probe of Geometric and Electronic Structure of Cobalt(II)-Substituted Proteins: Ground-State Zero-Field Splitting as a Coordination Number Indicator

Variable-temperature magnetic circular dichroism (VT MCD) is used as a probe of the ground-state electronic structure in Co(II)-substituted liver alcohol dehyrogenase, carbonic anhydrase, carboxypeptidase, substrate and inhibitor complexes of these enzymes, and four- and five-coordinate Co(II) model complexes. VT MCD was used to determine the magnitude of the ground-state zero-field splitting (ZFS) in these samples. The four-coordinate Co(II) species had ZFS's that ranged from 2.3 to 30 cm-1 and the five-coordinate species had ZFS's that ranged from 2.7 to 98 cm-1, values which fall outside of the ranges previously suggested for distinguishing 4-coordinate and 5-coordinate Co(II) (Makinen, M. W.; Kuo, L. C.; Yim, M. B.; Wells, G. B.; Fukuyama, J. M.; Kim, J. E. J. Am. Chem. Soc. 1985, 107, 5245−5255). The magnitude of the ZFS is not very sensitive to ligand heterogeneity but can be very sensitive to bond angles. Since protein active sites are in general highly angularly distorted from ideal four- or five-...

Photoemission and electronic structure of cobalt

Energy distribution curves (EDC's) of photoelectrons emitted normal to the surface have been measured for the (0001) and (10\ifmmode\bar\else\textasciimacron\fi{}10) single crystal faces and for evaporated polycrystalline films of cobalt. Incident photon energies of 11.83, 16.85, and 21.22 eV were used. The EDC's of the (0001) and (10\ifmmode\bar\else\textasciimacron\fi{}10) faces can be interpreted in terms of emission from electronic states characteristic of the one-dimensional bulk band structure along the corresponding symmetry lines. The maximum density of occupied states of the entire Brillouin zone is found to occur at ---0.35 \ifmmode\pm\else\textpm\fi{} 0.05 eV relative to the observed Fermi level. The density of states $N(E)$ for the ferromagnetic fcc phase has been calculated self-consistently by applying the Hubbard-model Hamiltonian. $N(E)$ at the Fermi level is obtained to be 0.65 and 0.99 electron/(atom eV) for the majority-spin and minority-spin states, respectively. The calculated $N(E)$ is consistent with the overall shapes of ultraviolet and x-ray photoelectron spectra. The present experimental and theoretical results agree with the requirements of the itinerant-electron model of ferromagnetism of the Slater-Stoner-Wohlfarth theory below the Curie point.

Electronic structure of cobalt

Results of KKR calculations using a Gaspar like potential are presented for paramagnetic cobalt in its fcc phase. The exchange energy contribution is reduced to just under 80% of the original Gaspar value to obtain a reasonable positioning of the d bands. The density of states is compared in detail with those arising from experimental and other theoretical investigations mainly for the hcp phase. The densities for both fcc and hcp phases are found to have much in common. The analysis is extended to the ferromagnetic case assuming rigid splitting of the paramagnetic bands. Adoption of the experimental magneton number leads to an exchange splitting of 1.92 eV and an electronic specific heat of 7.7*10-4 cal mol-1 K-2.

Effects of nitrogen donors on the electronic structure of cobalt(II) bis(dithioacetylacetonate)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of nitrogen donors on the electronic structure of cobalt(II) bis(dithioacetylacetonate)Kathleen M. Erck and Bradford B. WaylandCite this: Inorg. Chem. 1972, 11, 5, 1141–1143Publication Date (Print):May 1, 1972Publication History Published online1 May 2002Published inissue 1 May 1972https://doi.org/10.1021/ic50111a050RIGHTS & PERMISSIONSArticle Views47Altmetric-Citations10LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (405 KB) Get e-Alerts Get e-Alerts