Iterative partial equalization of orbital electronegativity – a rapid access to atomic charges

What is Solid State Chemistry? Preparative Methods. Characterization of Inorganic Solids: Application of Physical Techniques. Thermal Analysis. X-ray Diffraction. Point Groups, Space Groups and Crystal Structure. Descriptive Crystal Chemistry. Some Factors Which Influence Crystal Structure. Crystal Defects and Non-Stoichiometry. Solid Solutions. Interpretation of Phase Diagrams. Phase Transitions. Ionic Conductivity and Solid Electrolytes. Electronic Properties and Band Theory: Metals, Semiconductors, Inorganic Solids, Colour. Other Electrical Properties. Magnetic Properties. Optical Properties: Luminescence, Lasers. Glass. Cement and Concrete. Refractories. Organic Solid State Chemistry. Appendixes. Index.

Solid State Chemistry and its Applications

Electronic structure intrinsically controls the light absorbance, redox potential, charge-carrier mobility, and consequently, photoreactivity of semiconductor photocatalysts. The conventional approach of modifying the electronic structure of a semiconductor photocatalyst for a wider absorption range by anion doping operates at the cost of reduced redox potentials and/or charge-carrier mobility, so that its photoreactivity is usually limited and some important reactions may not occur at all. Here, we report sulfur-doped graphitic C(3)N(4) (C(3)N(4-x)S(x)) with a unique electronic structure that displays an increased valence bandwidth in combination with an elevated conduction band minimum and a slightly reduced absorbance. The C(3)N(4-x)S(x) shows a photoreactivity of H(2) evolution 7.2 and 8.0 times higher than C(3)N(4) under lambda > 300 and 420 nm, respectively. More strikingly, the complete oxidation process of phenol under lambda > 400 nm can occur for sulfur-doped C(3)N(4), which is impossible for C(3)N(4) even under lambda > 300 nm. The homogeneous substitution of sulfur for lattice nitrogen and a concomitant quantum confinement effect are identified as the cause of this unique electronic structure and, consequently, the excellent photoreactivity of C(3)N(4-x)S(x). The results acquired may shed light on general doping strategies for designing potentially efficient photocatalysts.

Unique Electronic Structure Induced High Photoreactivity of Sulfur-Doped Graphitic C3N4

The lithium-sulfur battery is receiving intense interest because its theoretical energy density exceeds that of lithium-ion batteries at much lower cost, but practical applications are still hindered by capacity decay caused by the polysulfide shuttle. Here we report a strategy to entrap polysulfides in the cathode that relies on a chemical process, whereby a host--manganese dioxide nanosheets serve as the prototype--reacts with initially formed lithium polysulfides to form surface-bound intermediates. These function as a redox shuttle to catenate and bind 'higher' polysulfides, and convert them on reduction to insoluble lithium sulfide via disproportionation. The sulfur/manganese dioxide nanosheet composite with 75 wt% sulfur exhibits a reversible capacity of 1,300 mA h g(-1) at moderate rates and a fade rate over 2,000 cycles of 0.036%/cycle, among the best reported to date. We furthermore show that this mechanism extends to graphene oxide and suggest it can be employed more widely.

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A highly efficient polysulfide mediator for lithium-sulfur batteries.

All of the x-ray emission wavelengths have recently been reevaluated and placed on a consistent \AA{}* scale. For most elements these data give a highly overdetermined set of equations for energy level differences, which have been solved by least-squares adjustment for each case. This procedure makes "best" use of all x-ray wavelength data, and also permits calculation of the probable error for each energy difference. Photoelectron measurements of absolute energy levels are more precise than x-ray absorption edge data. These have been used to establish the absolute scale for eighty-one elements and, in many cases, to provide additional energy level difference data. The x-ray absorption wavelengths were used for eight elements and ionization measurements for two; the remaining five were interpolated by a Moseley diagram involving the output values of energy levels from adjacent elements. Probable errors are listed on an absolute energy basis. In the original source of the present data, a table of energy levels in Rydberg units is given. Difference tables in volts, Rydbergs, and milli-\AA{}* wavelength units, with the respective probable errors, are also included there.

Reevaluation of x-ray atomic energy levels.

ESCA : atomic, molecular and solid state structure studied by means of electron spectroscopy

Electron spectra from an extensive series of sulfur compounds have been studied. A correlation has been established between the observed position of inner electron lines of sulfur and structure. The influence of structure on the electron binding energies is discussed in terms of a calculated atomic charge, based on the concepts of electronegativity and partial ionic character of bonds. The results are useful for the study of bonding and structure in sulfur chemistry, and are applied particularly to the discussion of the sulfur-oxygen bond (S=O).

A. Fahlman

Papers

ESCA : atomic, molecular and solid state structure studied by means of electron spectroscopy

Molecular Spectroscopy by Means of ESCA II. Sulfur compounds. Correlation of electron binding energy with structure

Charge transfer in transition metal carbides and related compounds studied by ESCA

Electron Spectroscopy and Chemical Binding

Binding energy of the "2p" electrons of silicon in various compounds