We have developed a quick-scanning x-ray absorption fine structure (QXAFS) system and installed it at the recently constructed synchrotron radiation beamline BL33XU at the SPring-8. Rapid acquisition of high-quality QXAFS data was realized by combining a servo-motor-driven Si channel-cut monochromator with a tapered undulator. Two tandemly aligned monochromators with channel-cut Si(111) and Si(220) crystals covered energy ranges of 4.0-28.2 keV and 6.6-46.0 keV, respectively. The system allows the users to adjust instantly the energy ranges of scans, the starting angles of oscillations, and the frequencies. The channel-cut crystals are cooled with liquid nitrogen to enable them to withstand the high heat load from the undulator radiation. Deformation of the reflecting planes is reduced by clamping each crystal with two cooling blocks. Performance tests at the Cu K-edge demonstrated sufficiently high data quality for x-ray absorption near-edge structure and extended x-ray absorption fine-structure analyses with temporal resolutions of up to 10 and 25 ms, respectively.
Highly
dense sulfonic acid-functionalized mesoporous electrolytes
with high proton conductivity under dry conditions were prepared using
tetramethoxysilane and 3-mercaptopropyltrimethoxysilane in the presence
of surfactants. Impedance spectroscopy and quasielastic neutron scattering
measurements showed that the proton conductive properties of the mesoporous
electrolytes depended significantly on the sulfonic acid densities
on the surface of the mesoporous walls. This finding was also supported
by molecular dynamics simulations. The proton conductivity of the
mesoporous electrolyte with the highest acid density of 3.1 SO3H molecules/nm2 showed a value of 0.3 mS/cm at
433 K even under dry conditions. This value was higher than that for
Nafion by about 2 orders of magnitude. Such high proton conductivity
is thought to be induced by proton hopping in the hydrogen-bonded
networks that were predominantly formed by neighboring sulfonic acid
groups.
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