The remote hydrogen plasma is able to create abundant S‐vacancies on amorphous molybdenum sulfide (a‐MoSx) as active sites for hydrogen evolution. The results demonstrate that the plasma‐treated ...a‐MoSx exhibits superior performance and higher stability than Pt in a proton exchange membrane based electrolyzers measurement as a proof‐of‐concept of industrial application.
High pressure (HP) can drive the direct sintering of nanoparticle assemblies for Ag/Au, CdSe/PbS nanocrystals (NCs). Instead of direct sintering for the conventional nanocrystals, this study ...experimentally observes for the first time high‐pressure‐induced comminution and recrystallization of organic–inorganic hybrid perovskite nanocrystals into highly luminescent nanoplates with a shorter carrier lifetime. Such novel pressure response is attributed to the unique structural nature of hybrid perovskites under high pressure: during the drastic cubic–orthorhombic structural transformation at ≈2 GPa, (301) the crystal plane fully occupied by organic molecules possesses a higher surface energy, triggering the comminution of nanocrystals into nanoslices along such crystal plane. Beyond bulk perovskites, in which pressure‐induced modifications on crystal structures and functional properties will disappear after pressure release, the pressure‐formed variants, i.e., large (≈100 nm) and thin (<10 nm) perovskite nanoplates, are retained and these exhibit simultaneous photoluminescence emission enhancing (a 15‐fold enhancement in the photoluminescence) and carrier lifetime shortening (from ≈18.3 ± 0.8 to ≈7.6 ± 0.5 ns) after releasing of pressure from 11 GPa. This pressure‐induced comminution of hybrid perovskite NCs and a subsequent amorphization–recrystallization treatment offer the possibilities of engineering the advanced hybrid perovskites with specific properties.
High pressure (up to tens of gigapascals), as a clean and powerful tool, can effectively alter crystal structures. It is experimentally investigated for the first time whether pressure can regulate the comminution and recrystallization of MAPbBr3 nanocrystals. The initial nanocrystals slide into nanoslices during phase transformation to the orthorhombic polymorph, followed by recrystallization into nanoplates upon amorphization.
We analyzed the adsorption of Li on graphene in the context of anodes for lithium-ion batteries (LIBs) using first-principles methods including van der Waals interactions. We found that although Li ...can reside on the surface of defect-free graphene under favorable conditions, the binding is much weaker than to graphite and the concentration on a graphene surface is not higher than in graphite. At low concentration, Li ions spread out on graphene because of Coulomb repulsion. With increased Li content, we found that small Li clusters can be formed on graphene. Although this result suggests that graphene nanosheets can conceivably have a higher ultimate Li capacity than graphite, it should be noted that such nanoclusters can potentially nucleate Li dendrites, leading to failure. The implications for nanostructured carbon anodes in batteries are discussed.
Boron nitride (BN) domains are easily formed in the basal plane of graphene due to phase separation. With first-principles calculations, it is demonstrated theoretically that the band gap of graphene ...can be opened effectively around K (or K') points by introducing small BN domains. It is also found that random doping with boron or nitrogen is possible to open a small gap in the Dirac points, except for the modulation of the Fermi level. The surface charges which belong to the π states near Dirac points are found to be redistributed locally. The charge redistribution is attributed to the change of localized potential due to doping effects. The band opening induced by the doped BN domain is found to be due to the breaking of localized symmetry of the potential. Therefore, doping graphene with BN domains is an effective method to open a band gap for carbon-based next-generation microelectronic devices.
Infrared spectra for a series of asymmetric proton‐bound dimers with protonated trimethylamine (TMA‐H+) as the proton donor were recorded and analyzed. The frequency of the N–H+ stretching mode is ...expected to red shift as the proton affinity of proton acceptors increases. The observed band, however, shows a peculiar splitting of approximately 300 cm−1 with the intensity shifting pattern resembling a two‐level system. Theoretical investigation reveals that the observed band splitting and its extraordinarily large gap of around 300 cm−1 is a result of strong coupling between the fundamental of the proton stretching mode and overtone states of the two proton bending modes, that is commonly known as Fermi resonance (FR). We also provide a general theoretical model to link the strong FR coupling to the quasi‐two‐level system. Since the model does not depend on the molecular specification of TMA‐H+, the strong coupling we observed is an intrinsic property associated with proton motions.
Huge Fermi resonance coupling was found in the experimental IR predissociation spectra of proton‐bound dimers based on protonated trimethylamine (TMA‐H+). An ab initio anharmonic vibrational analysis could explain the quasi‐two‐level behavior of the multiple states in the Fermi resonance as the proton affinity of proton acceptors varies.
Tungsten ditelluride (WTe2) is a semimetal with orthorhombic Td phase that possesses some unique properties such as Weyl semimetal states, pressure‐induced superconductivity, and giant ...magnetoresistance. Here, the high‐pressure properties of WTe2 single crystals are investigated by Raman microspectroscopy and ab initio calculations. WTe2 shows strong plane‐parallel/plane‐vertical vibrational anisotropy, stemming from its intrinsic Raman tensor. Under pressure, the Raman peaks at ≈120 cm−1 exhibit redshift, indicating structural instability of the orthorhombic Td phase. WTe2 undergoes a phase transition to a monoclinic T′ phase at 8 GPa, where the Weyl states vanish in the new T′ phase due to the presence of inversion symmetry. Such Td to T′ phase transition provides a feasible method to achieve Weyl state switching in a single material without doping. The new T′ phase also coincides with the appearance of superconductivity reported in the literature.
The plane‐parallel/plane‐vertical vibrational anisotropies of WTe2 single crystal under high pressure are investigated by Raman spectroscopy and ab initio calculations. WTe2 undergoes a phase transition from orthorhombic Td to monoclinic T′ phase at 8 GPa, where the Weyl states vanish in the new T′ phase due to the presence of inversion symmetry.
By the incorporation of C into (BN)12 fullerene, our theoretical investigation shows that the hydrogenation reaction on carbon doped B11N12C cluster is both thermodynamically favored and kinetically ...feasible under ambient conditions. Without using the metal catalyst, the C atom can work as an activation center to dissociate H2 molecule and provide the free H atom for further hydrogenation on the B11N12C fullerene, which saves the materials cost in practical applications for hydrogen storage. Moreover, the material curvature also plays an important role in reducing the activation barrier for the hydrogen dissociation on the BN fullerenes.
► The kinetics of the hydrogenation reaction on C-doped BN fullerene was studied. ► The C atom works as an activation center for the hydrogen dissociation. ► The hydrogenation on C-doped BN fullerene is a metal free and self-catalyzed process. ► C doping can effectively modify the hydrogen storage property of the BN fullerene. ► There is a curvature effect on the hydrogenation kinetics of BN fullerenes.
To explore the impact of fluorination on the hydrogen bond networks of protonated alkylalcohols, infrared spectroscopy and theoretical computations of protonated 2,2,2-trifluoroethanol clusters, H
...(TFE)
, (
= 4-7), were performed. It has been demonstrated that the development of the hydrogen bond networks from a linear type to cyclic types occurs in this size region for the protonated alkylalcohol clusters. In contrast, infrared spectroscopy of H
(TFE)
in the OH/CH stretch region clearly indicated that the linear type structures are held in the whole size range, irrespective of temperature of the clusters. The extensive stable isomer structure search of H
(TFE)
based on our latest sampling approach supported the strong preference of the linear type hydrogen bond networks. Detailed analyses of the free OH stretching vibrational bands evidenced the intra- and intermolecular OH⋯FC interactions in the clusters. In addition, infrared spectra of protonated clusters of 2,2-difluoroethanol, 2,2-difluoropropanol, and 3,3,3-trifluoropropanol were measured for
= 4 and 5, and their spectra also indicated the effective inhibition of the cyclic hydrogen bond network formation by the fluorination.
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