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Lipson A.L.,Chemical science and Engineering Division | Lipson A.L.,Argonne National Laboratory | Pan B.,Chemical science and Engineering Division | Pan B.,Argonne National Laboratory | And 7 more authors.
Chemistry of Materials | Year: 2015

As new uses for larger scale energy storage systems are realized, new chemistries that are less expensive or have higher energy density are needed. While lithium-ion systems have been well studied, the availability of new energy storage chemistries opens up the possibilities for more diverse strategies and uses. One potential path to achieving this goal is to explore chemistries where a multivalent ion such as Ca2+ or Mg2+ is the active species. Herein, we demonstrate this concept for a Ca-ion system utilizing manganese hexacyanoferrate (MFCN) as the cathode to intercalate Ca reversibly in a dry nonaqueous electrolyte. Through characterization via X-ray absorption near-edge spectroscopy, it is determined that only the manganese changes oxidation state during cycling with Ca. X-ray diffraction indicates the MFCN maintains its crystallinity during cycling, with only minor structural changes associated with expansion and contraction. Furthermore, we have demonstrated the first rechargeable Ca-ion battery utilizing MFCN as the cathode and elemental tin as the anode. © 2015 American Chemical Society. Source

Wang J.,X ray Science Division | Wang J.,University of Utah | Winans R.E.,X ray Science Division | Anderson S.L.,University of Utah | And 6 more authors.
Journal of Physical Chemistry C | Year: 2013

The generation and growth of nanoparticles by thermal decomposition of organo-Pd precursors in toluene solution has been studied using in situ small-angle X-ray scattering. The results show that detectable concentrations of particles begin to form at solution temperatures above 130 C, and both the size and volume of the particles increase with heating temperature and time. The radius of the particles detected ranges from 0.5 ± 0.1 nm to a few nanometers, depending on the temperature and heating time. The structure of the particles was probed by measurement of pair distribution functions, which demonstrated that the particles have structure identical to bulk metallic Pd. The identification of the particles as metallic Pd was confirmed by X-ray absorption near-edge structure spectroscopy, and transmission electron microscopy. © 2013 American Chemical Society. Source

Chen L.X.,Chemical science and Engineering Division | Chen L.X.,Northwestern University | Zhang X.,X ray Science Division | Wasinger E.C.,Chemical science and Engineering Division | And 7 more authors.
Chemical Science | Year: 2010

Axial ligation mechanisms of a metalloporphyrin, nickel(ii) tetramesitylporphyrin (NiTMP), were investigated by static and transient X-ray absorption spectroscopy at Ni K-edge (8.333 keV). A surprisingly broad (i.e. ∼1.4 eV) linewidth for the 1s → 3dx2-y2 transition in the ground state was attributed to strong geometry dependent 3d molecular orbital (MO) energies due to coexisting conformers in solution. The broad distribution of 3d MO energy levels enables transient degeneracy of the 3dz2 and 3dx2-y2 MOs to produce a temporary vacancy in the 3dz2 MO which favors axial ligation. Photoexcitation also induces the vacancy in the 3dz2 MO, leading to a more than two-fold enhancement in the axial ligated species. Therefore, a unified axial ligation mechanism for both the ground and excited state is proposed based on the elucidation of the excited state structural dynamics, which will have a broad impact in understanding and controlling axial ligation in enzymatic reactions and molecular catalysis involving transient axial ligation. © 2010 The Royal Society of Chemistry. Source

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