5 research outputs found
High-Throughput Screening for Boride Superconductors
A high-throughput
screening using density functional calculations
is performed to search for stable boride superconductors from the
existing materials database. The workflow employs the fast frozen-phonon
method as the descriptor to evaluate the superconducting properties
quickly. Twenty-three stable candidates were identified during the
screening. The superconductivity was obtained earlier experimentally
or computationally for almost all found binary compounds. Previous
studies on ternary borides are very limited. Our extensive search
among ternary systems confirmed superconductivity in known systems
and found several new compounds. Among these discovered superconducting
ternary borides, TaMo2B2 shows the highest superconducting
temperature of ∼12 K. Most predicted compounds were synthesized
previously; therefore, our predictions can be examined experimentally.
Our work also demonstrates that the boride systems can have diverse
structural motifs that lead to superconductivity
Ammonia Electrosynthesis with High Selectivity under Ambient Conditions via a Li<sup>+</sup> Incorporation Strategy
We report the discovery of a dramatically
enhanced N<sub>2</sub> electroreduction reaction (NRR) selectivity
under ambient conditions
via the Li<sup>+</sup> incorporation into poly(<i>N</i>-ethyl-benzene-1,2,4,5-tetracarboxylic
diimide) (PEBCD) as a catalyst. The detailed electrochemical evaluation
and density functional theory calculations showed that Li<sup>+</sup> association with the O atoms in the PEBCD matrix can retard the
HER process and can facilitate the adsorption of N<sub>2</sub> to
afford a high potential scope for the NRR process to proceed in the
“[OLi<sup>+</sup>]·N<sub>2</sub>H<sub><i>x</i></sub>” alternating hydrogenation mode.
This atomic-scale incorporation strategy provides new insight into
the rational design of NRR catalysts with higher selectivity
Understanding the High Capacity of Li<sub>2</sub>FeSiO<sub>4</sub>: In Situ XRD/XANES Study Combined with First-Principles Calculations
The
electrochemical mechanism of the cathode material Li<sub>2</sub>FeSiO<sub>4</sub> with reversible extraction/insertion of more than
one Li<sup>+</sup> from/into the structure has been studied by techniques
of in situ synchrotron X-ray
absorption near edge structure (XANES) and X-ray diffraction (XRD).
These advanced techniques provide effective solutions to address the
limitations of characterization by traditional ex situ methods. The
study of in situ Fe K-edge XANES indicates that the Fe ion in the
Li<sub>2</sub>FeSiO<sub>4</sub> is oxidized continuously to high valence
during the charging process from open circuit potential to 4.8 V,
which contributes to the high reversible capacities of the materials.
In situ XRD and theoretical study from first-principles calculations
have been employed to reveal the structural evolution of the Li<sub>2</sub>FeSiO<sub>4</sub> underlying the high capacity during the
charge/discharge process. The results of both experimental and theoretical
studies are consistent and indicate that Li<sub>2</sub>FeSiO<sub>4</sub> undergoes two two-phase reactions when the electrode is charged
to a high voltage of 4.8 V
Zero-Strain Na<sub>2</sub>FeSiO<sub>4</sub> as Novel Cathode Material for Sodium-Ion Batteries
A new cubic polymorph of sodium iron
silicate, Na<sub>2</sub>FeSiO<sub>4</sub>, is reported for the first
time as a cathode material for Na-ion batteries. It adopts an unprecedented
cubic rigid tetrahedral open framework structure, i.e., <i>F</i>4̅3<i>m</i>, leading to a polyanion cathode material
without apparent cell volume change during the charge/discharge processes.
This cathode shows a reversible capacity of 106 mAh g<sup>–1</sup> and a capacity retention of 96% at 5 mA g<sup>–1</sup> after
20 cycles