By
first-principles calculation and experimental measurements,
we investigated the lithiation process in the Ti4C3 and Ti2Ta2C3 MXenes. Our
results show the successful synthesis of the Ti2Ta2C3 MXene with an interlayer distance of 0.4 nm,
which supposes the correct delamination of the material. Our measurements
also demonstrate that the double-ordered alloy Ti2Ta2C3 can store 4 times the amount of lithium than
the pristine Ti4C3 MXene. By DFT calculation,
we investigated the stability of the Ti
x
Ta4–x
C3 MXenes. According
to the calculations, five MXenes are stable, where the most stable
50% Ta/Ti ratio structure (Ti2Ta2C3) presents a chemically ordered composition. The Li intercalation
processfor Ti4C3 and Ti2Ta2C3 MXenesis carried out as adatoms on the
surface, with the T4 site being the most favorable. The chemically
ordered MXenes provide better OCV values and can store more Li atoms
than the Ti4C3 MXene. Also, the Li diffusion
process demonstrates that Ti2Ta2C3 is a more efficient material to be employed as an anode in batteries
since it provides the lowest energy barriers. Our results demonstrate
the capability of the Ti2Ta2C3 alloy
to be employed in energy storage applications thanks to the high stability
and capacity to store Li ions in comparison with pristine Ti4C3 MXene.
Carbon-protected BiVO4 photoanode and Cu2O photocathode tandem photoelectrochemical (PEC) system has been explored to reduce surface recombination and enhance the stability of the photoelectrodes. In addition to the carbon layer, the electrodeposited FeOOH nanolayer and drop-casted MoS2 co-catalyst layer on the photoanode and photocathode, respectively improve the reaction kinetics. The optimized photoanode (Mo-BiVO4/C/FeOOH) and photocathode (Cu2O/C/MoS2) produces current densities of ~1.22 mA cm−2 at 1.23 V vs. RHE and ~−1.48 mA cm−2 at 0 V vs. RHE, respectively. The obtained photocurrent is higher than bare photoelectrodes without a carbon layer. Finally, a tandem cell has been constructed, and an unassisted current density of ~0.107 mA cm−2 is obtained for a carbon-protected BiVO4–Cu2O tandem PEC cell at zero bias. The improved stability and enhanced photocurrent of the carbon protective layer are attributed to its better charge transfer resistance and minimized surface defects. Carbon protective layer can be a viable option to improve the stability of photoelectrodes in aqueous media.
In this work, a facile synthesis of multilayer graphene oxide (GO) sheets having a two-dimensional structure has been realized using the modified Hummers and Offeman method. The as-synthesized GO was analyzed by UV-visible, FTIR, Powder X-ray Diffraction (PXRD), HRTEM, FESEM, and EDX for optical, chemical, structural, morphological, topographical, and elemental analysis respectively. The results reveal that GO shows an absorption band at 232 nm. The FTIR spectrum shows the oxygen-rich groups in GO, and PXRD confirms the major GO peak at 10.35° along with few minor peaks. HRTEM and FESEM confirm the two-dimensional GO sheets along with high lateral dimensions. The as-synthesized GO with a number of available functional groups and high lateral dimension was efficiently used for the photocatalytic degradation of Coralline Red BS (CR BS) and Reactive Blue 81 (RB81) dyes. This study reveals that, compared to graphene, pristine GO sheets significantly influence the degradation of CR BS and RB81 dyes. This work significantly contributes to the use of pristine GO for the removal of toxic dyes from wastewater. The evaluation of the dye degradation rate and GO reusability along with the kinetic studies is explained in detail.
Much is still not known about the end-state of core materials in each unit that was operating on March 11, 2011 at the Fukushima Daiichi Nuclear Power Station (Daiichi). Information obtained from Daiichi is required to inform Decontamination and Decommissioning (D&D) activities, improving the ability of the Tokyo Electric Power Company Holdings, Incorporated (TEPCO Holdings) to characterize potential hazards and to ensure the safety of workers involved with cleanup activities. This information also has important implications for the safety and operation of U.S. commercial nuclear power plants. This document summarizes results from the Fiscal Year 2021 (FY2021) U.S. effort to review Daiichi information and extract insights to enhance the safety of existing and future nuclear power plant designs. This U.S. effort, which was initiated in 2014 by the Department of Energy Office of Nuclear Energy (DOE-NE), is completed by a group of experts in reactor safety and plant operations that identify examination needs and evaluate recent Daiichi examination data to address these needs. Since its inception, annual reports were issued that document significant safety insights being obtained in areas of special emphasis: system and component performance, radionuclide surveys and sampling, debris end-state location, combustible gas effects, and plant operations and maintenance. In addition to reducing uncertainties related to severe accident modeling progression, these insights have and continue to be used to update guidance for severe accident prevention, mitigation, and emergency planning. Reduced uncertainties in modeling the events at Daiichi improve the realism of reactor safety evaluations that inform future D&D activities.A key aspect of prior U.S. efforts, the updated list of information requests, is included in this FY2021 report to ensure that they are transmitted to organizations within Japan. This report also continues to emphasize how information obtained from the affected reactors at Daiichi has been and will continue to be used to update severe accident management strategies and reduce uncertainties in systems analysis code models. In addition, recommendations are included that would expand the use of this information to provide insights regarding maintenance, radiation protection, design, and siting activities for existing and new reactors.
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