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Molecular Design Strategy in Dye-sensitized Photoelectrochemical Cells for the Lignin Oxidation
No full textLignocellulosic biomass comprises lignin, cellulose, and hemicellulose and is the largest renewable carbon source on earth. The conversion of lignin represents an alternative to petroleum as a source for the production of aromatic compounds that serve as feedstocks for aviation fuels. The prospect of using lignin as a renewable and alternative source of aromatic compounds in place of petroleum has motivated several approaches for carrying out lignin depolymerization, but controlling the extent of the reaction to afford specific products remains a significant challenge. To overcome this issue, dye-sensitized photoelectrochemical cells have emerged for the visible-light-driven selective cleavage of the C???C/C???O bond in lignin model compounds at ambient temperature. However, these recent works have been limited to studying a relatively simple Ruthenium dye with limited tunable redox potentials. Compared with metal complexes like ruthenium dyes, the energy levels of organic dyes can be easily tuned by controlling donor????????acceptor (D????????A) configuration. This is because the organic dyes are designed with ??-conjugated organic segments in a donor????????acceptor (D????????A) configuration, and their photophysical properties can be easily tuned by changing the molecular units. Especially, the controlling donor units in organic dyes are very important to study the mechanism of catalyzed cleavage of lignin. My group has studied organic dyes for over 10 years. In this presentation, I will present the molecular design strategy of controlling the donor energy level and the efficient charge transfer for photocatalytic oxidative C???C/C???O bonds cleavage in the DSPEC
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No full textA Kinetic Indicator of Ultrafast Nickel-Rich Layered Oxide Cathodes
No full textElucidating high-rate cycling-induced nonequilibriumelectrodereactions is crucial for developing extreme fast charging (XFC) batteries.Herein, we unveiled the distinct rate capabilities of a series ofNi-rich layered oxide (NRLO) cathodes by quantitatively establishingtheir dynamic structure-kinetics relationships. Contrary toconventional views, we discovered electrode kinetic properties obtained ex-situ near equilibrium states failed to assess the effectiverate capability of NRLOs at ultrafast C rates. Further, the kineticphase heterogeneity, characterized by the dynamic separations in in-situ X-ray diffraction patterns and deviations in NRLO c-axis lattice parameters, exclusively correlated with thecapacity reduction under XFC and became an effective indicator ofthe NRLO rate capability. Enhancing the cycling temperature boostedthe rate capability of studied NRLOs by similar to 10%, which was furtherverified to mitigate the kinetic phase heterogeneity during XFC. Overall,this study lays the groundwork for tuning the kinetic phase heterogeneityof electrodes to develop ultrafast batteries
Examination of sulfate resistance of nano-alumina added ordinary Portland cement paste, focusing on the two different crystallinity of nano-aluminas
No full textThis study examined the influence of the crystallinity of added nano-alumina on the sulfate resistance of ordinary Portland cement (OPC) paste. Two crystalline types of nano-aluminas (a-and ?-phase) were incorporated in cement pastes, which were exposed to sulfate solution. In the results, both paste samples having a- and ?-phase aluminas had accelerated compressive strength loss and increased length expansion compared to the sample without alumina addition. In particular, the rapidly decreased dynamic elastic modulus of the nano-alumina added samples postulates the greatly increased internal stress likely by the increased formation of volume expansive reaction products, such as ettringite, which was supported by the XRD and TG results. The greater ettringite formation in the nano-alumina added samples was likely due to reactive AH(3) (=Al(OH)(3)) gel formation as the higher consumption degree of portlandite in the alumina added samples indirectly indicates the active AH(3) gel formation, resulting in additional ettringite formation from the reaction of AH(3) with Na2SO4 solution. A further degree of sulfate attack was observed in the ?-alumina added sample for the long-term Na2SO4 exposure (180 days) mainly due to the greater degree of gypsum formation inducing more internal expansive stress compared to the a-alumina added sample
Fully inkjet-printed large-scale photoelectrodes
No full textSmall-area photoelectrodes are used to study fundamental science and material development for photoelectrochemical (PEC) water splitting cells at the laboratory scale. For practical applications, however, one needs to develop scalable geometrical designs and architectures of large photoelectrodes as well as their fabrication using low-cost, solution-processed, scalable methods. In this perspective, we first discuss the device physics concepts for devel-oping large photoelectrodes using dimensional engineering (size, geometry, shape, and structures) and scalable architectures (such as symmetric and asymmetric designs with gridlines as well as mono-lithically integrated modules with interconnections), similar to the earlier development of large thin-film photovoltaic cells. Finally, we propose a novel and strategic protocol to fabricate these designs for the development of large-photoelectrode modules via commercially deployable, fully inkjet-printing as a solution pro-cessed thin-film deposition method
Electron-Ion Temperature Ratio in Astrophysical Shocks
No full textCollisionless shock waves in supernova remnants and the solar wind heat electrons less effectively than they heat ions, as is predicted by kinetic simulations. However, the values of T ( e )/T ( p ) inferred from the H alpha profiles of supernova remnant shocks behave differently as a function of Mach number or Alfven Mach number than what is measured in the solar wind or predicted by simulations. Here we determine T ( e )/T ( p ) for supernova remnant shocks using H alpha profiles, shock speeds from proper motions, and electron temperatures from X-ray spectra. We also improve the estimates of sound speed and Alfven speed used to determine Mach numbers. We find that the H alpha determinations are robust and that the discrepancies among supernova remnant shocks, solar wind shocks, and computer-simulated shocks remain. We discuss some possible contributing factors, including shock precursors, turbulence, and varying preshock conditions