Lyotropic Liquid Crystalline Mesophases Made of Salt-Acid-Surfactant Systems for the Synthesis of Novel Mesoporous Lithium Metal Phosphates

Nanoarchitectonics of Mesoporous M2P2O7 (M = Mn(II), Co(II), and Ni(II)) and M2-xCoxP2O7 and Transformation to Their Metal Hydroxides with Decent Charge Capacity in Alkali Media

A general synthetic method has been developed to synthesize spherical mesoporous metal pyrophosphate (m-M2P2O7) particles and to fabricate graphite rod-coated (GR-M2P2O7) electrodes, which are important as energy storage materials. The clear aqueous solution of the ingredients (namely, [M(H2O)6](NO3)2, H4P2O7, water, and P123) assembles, upon excess water evaporation, into a mesostructured M2HxP2O7(NO3)x·nH2O-P123 semisolid that is calcined to produce the spherical m-M2P2O7 (where M is Ni, Co, Mn, Ni/Co, or Mn/Co) particles, coated over GR, and calcined to fabricate the GR-M2P2O7 electrodes. The mesostructured and mesoporous materials are characterized using diffraction (XRD), spectroscopy (ATR-FTIR, XPS, and EDX), N2 adsorption-desorption, and imaging (SEM and TEM) techniques. The electrochemical/chemical investigations showed that the GR-M2P2O7 electrodes transform to β-M(OH)2 in alkali media. The spherical m-Ni2P2O7 particles transform into spherical ultrathin nanoflakes of β-Ni(OH)2. However, the m-Mn2P2O7 and m-Co2P2O7 particles transform to much thicker β-Mn(OH)2 and β-Co(OH)2 plate-like nanoparticles, respectively. The size and morphology of the β-M(OH)2 particle depend on the Ksp of the M2P2O7 and determine the charge capacity (CC) and specific capacitance (SC) of the electrodes. The β-Ni(OH)2 and β-Ni0.67Co0.33(OH)2 electrodes display high CC (129 and 170 mC/cm2, respectively) and SC (234.5 and 309 mF/cm2, respectively) values. However, these values are almost 10× smaller in β-Mn(OH)2, β-Co(OH)2, β-Mn1-xCox(OH)2, and cobalt-rich β-Ni1-xCox(OH)2 electrodes.

Lyotropic Liquid Crystalline Mesophases of Lithium Dihydrogen Phosphate and 10-Lauryl Ether Stabilized with Water or Phosphoric Acid

The molten phase of transition metal and lithium salts self-assemble with non-ionic surfactants to form lyotropic liquid crystalline (LLC) mesophases, which are important in the development of gel-electrolytes and mesoporous materials. Here, we show that LiH₂ PO₄ forms a semi-stable LLC mesophase with 10-lauryl ether (C₁₂ H₂₅ (OCH₂ CH₂ )₁₀ OH, C₁₂ E₁₀ ), decoded as Li-EO-X (X is LiH₂ PO₄ /C₁₂ E₁₀ mole ratio and between 2 and 200). The stability of the Li-EO-X phase is improved by increasing salt concentration (X>20) in the media. The semi-stable Li-EO-X mesophase is further stabilized by adding either water by controlling the humidity or H₃ PO₄ (PA) to the media. The phase behaviour of the above samples was investigated using POM, XRD, conductivity, and ATR-FTIR measurements. The addition of PA not only brings stability and higher conductivity (increase from 0.1 to 8.9 mS/cm) to the mesophase but also produce an LLC gel-electrolyte with a high buffer capacity that may be useful and important in various applications.

Emergence of the first XAFS/XRF beamline in the Middle East: providing studies of elements and their atomic/electronic structure in pluridisciplinary research fields

XAFS/XRF is a general-purpose absorption spectroscopy beamline at the Synchrotron-light for Experimental Science and Applications in the Middle East (SESAME), Jordan. Herein, its optical layout is presented along with its powerful capabilities in collecting absorption and fluorescence spectra within a wide energy range (4.7-30 keV). The beamline is equipped with a conventional fixed-exit double-crystal monochromator that allows the collection of an X-ray absorption spectrum within a few minutes in step-by-step mode. An on-the-fly scanning mode will be implemented shortly where the acquisition time will be reduced to less than a minute per scan. The full automation of the beamline allows performing successive measurements under different conditions. The different experimental setups and special features available to users are reported. Examples of XRF and XAFS measurements are presented, showing the performance of the beamline under different standard conditions.