Na_(3)P interphase reduces Na nucleation energy enabling stable anode-less sodium metal batteries

Sodium metal batteries(SMBs)are rising as viable alternatives to lithium-ion systems due to their superior energy density and sodium's relative abundance.However,SMBs face significant impediments,particularly the exceedingly high negative-to-positive capacity ratios(N/P ratios)which severely encumber energy density and hinder their practical application.Herein,a novel nucleophilic Na_(3)P interphase on aluminum foil has been designed to significantly lower the nucleation energy barrier for sodium atom deposition,resulting in a remarkable reduction of nucleation overpotential and efficient mitigation of dendritic growth at high sodium deposition of 5 mA h cm^(−2).The interphase promotes stable cycling in anode-less SMB configurations with a low N/P ratio of 1.4 and high cathode mass loading of 11.5 mg cm^(−2),and demonstrates a substantial increase in high capacity retention of 92.4%after 500 cycles even under 1 C rate condition.This innovation signifies a promising leap forward in the development of high-energy-density,anode-less SMBs,offering a potential solution to the longstanding issues of cycle stability and energy efficiency.

Surface stabilized cubic phase of CsPbI_3 and CsPbBr_3 at room temperature

Inorganic halide perovskites CsPb X_3(X = I, Br) have attracted tremendous attention in solar cell applications. However, the bulk form of the cubic phase CsPb X_3, which offers moderate direct bandgaps, is metastable at room temperature and tends to transform into a tetragonal or orthorhombic phase. Here, our density functional theory calculation results found that the surface energies of the cubic phase are smaller than those of the orthorhombic phase, although the bulk counterpart of the cubic phase is less stable than that of the orthorhombic phase. These results suggest a surface stabilization strategy to maintain the stability of the cubic phase at room temperature that an enlarged portion of surfaces shall change the relative stability of the two phases in nanostructured CsPb X_3. This strategy, which may potentially solve the long-standing stability issue of cubic CsPb X_3, was demonstrated to be feasible by our calculations in zero-, one-, and two-dimensional nanostructures. In particular, confined sizes from few to tens of nanometers could keep the cubic phase as the most thermally favored form at room temperature. Our predicted values in particular cases, such as the zero-dimensional form of CsPbI_3,are highly consistent with experimental values, suggesting that our model is reasonable and our results are reliable. These predicted critical sizes give the upper and lower limits of the confined sizes, which may guide experimentalists to synthesize these nanostructures and promote likely practical applications such as solar cells and flexible displays using CsPb X_3 nanostructures.

Quasi-One-Dimensional Free-Electron-Like States Selected by Intermolecular Hydrogen Bonds at the Glycine/Cu(100) Interface

We carry out ab initio density functional theory calculations to study manipulation of electronic structures of selfassembled molecular nanostructures on metal surfaces by investigating the geometric and electronic properties of glycine molecules on Cu(100).It is shown that a glycine monolayer on Cu(100)forms a two-dimensional hydrogen-bonding network between the carboxyl and amino groups of glycine using a first principles atomistic calculation on the basis of a recently found structure.This network includes at least two hydrogen-bonding chains oriented roughly perpendicular to each other.Through molecule–metal electronic hybridization,these two chains selectively hybridized with the two isotropic degenerate Cu(100)surface states,leading to two anisotropic quasi-one-dimensional surface states.Electrons occupying these two states can near-freely move from a molecule to its adjacent molecules directly through the intermolecular hydrogen bonds,rather than mediated by the substrate.This results in the experimentally observed anisotropic free-electron-like behavior.Our results suggest that hydrogen-bonding chains are likely candidates for charge conductors.

Al_(1-x)Sc_(x)Sb_(y)N_(1-y):An opportunity for ferroelectric semiconductor field effect transistor

For the in-memory computation architecture,a ferroelectric semiconductor field-effect transistor(FeSFET)incorporates ferroelectric material into the FET channel to realize logic and memory in a single device.The emerging groupⅢnitride material Al_(1-x)Sc_(x)N provides an excellent platform to explore FeSFET,as this material has significant electric polarization,ferroelectric switching,and high carrier mobility.However,steps need to be taken to reduce the large band gap of~5 eV of Al_(1-x)Sc_(x)N to improve its transport property for in-memory logic applications.By state-of-the-art first principles analysis,here we predict that alloying a relatively small amount(less than~5%)of Sb impurities into Al_(1-x)Sc_(x)N very effectively reduces the band gap while maintaining excellent ferroelectricity.We show that the co-doped Sb and Sc act cooperatively to give a significant band bowing leading to a small band gap of~1.76 eV and a large polarization parameter~0.87 C/m^(2),in the quaternary Al_(1-x)Sc_(x)Sb_(y)N_(1-y)compounds.The Sb impurity states become more continuous as a result of interactions with Sc and can be used for impurity-mediated transport.Based on the Landau-Khalatnikov model,the Landau parameters and the corresponding ferroelectric hysteresis loops are obtained for the quaternary compounds.These findings indicate that Al_(1-x)Sc_(x)Sb_(y)N_(1-y)is an excellent candidate as the channel material of FeSFET.

Understanding synergistic catalysis on Pt–Cu diatomic sites via operando X-ray absorption spectroscopy in sulfur redox reactions

Sulfur redox reactions render lithium–sulfur(Li–S)batteries with an energy density of>500Whkg−1 but suffer a low practical capacity and fast capacity fade due to sluggish sulfur redox reaction(SRR)kinetics,which lies in the complex reaction process that involves a series of reaction intermediates and proceeds via a cascade reaction.Here,we present a Pt–Cu dual-atom catalyst(Pt/Cu-NG)as an electrocatalyst for sulfur redox reactions.Pt/Cu-NG enabled the rapid conversion of soluble polysulfide intermediates into insoluble Li2S2/Li2S,and consequently,it prevented the accumulation and shuttling of lithium polysulfides,thus outperforming the corresponding single-atom catalysts(SACs)with individual Pt or Cu sites.Operando X-ray absorption spectroscopy and density functional theory calculations revealed that a synergistic effect between the paired Pt and Cu atoms modifies the electronic structure of the Pt site through d-orbital interactions,resulting in an optimal moderate interaction of the metal atom with the different sulfide species.This optimal interaction enhanced charge transfer kinetics and promoted sulfur redox reactions.Our work thus provides important insights on the atomic scale into the synergistic effects operative in dual-atom catalysts and will thus pave the way to electrocatalysts with enhanced efficiency for high-performance Li–S batteries.

One-pot synthesis of toluene from methane and methanol catalyzed by GaN nanowire

The generation of aromatic benzene,toluene,xylene(BTX)compounds from non-petroleum feedstocks is of particular interest for chemists in the eyes of sustainability.Herein,a novel synthesis of toluene catalyzed by GaN semiconductor nanowire arrays is reported.Using methane and methanol as starting materials,the GaN nanowire arrays can synergistically facilitate the facile generation of toluene under either photo-irradiation or thermal-conditions.The detailed computational studies unveiled different mechanisms involved for the photo-and thermal-toluene synthesis.

Cobalt and nitrogen atoms co-doped porous carbon for advanced electrical double-layer capacitors

Electrical double-layer capacitors are widely concerned for their high power density,long cycling life and high cycling efficiency.However,their wide application is limited by their low energy density.In this study,we propose a simple yet environmental friendly method to synthesize cobalt and nitrogen atoms co-doped porous carbon(CoAT-NC) material.Cobalt atoms connected with primarily pyridinic nitrogen atoms can be uniformly dispersed in the amorphous carbon matrix,which is benefit for improving electrical conductivity and density of states of the carbon material.Therefore,an enhanced perfo rmance is expected when CoAT-NC is served as electrode in a supercapacitor device.CoAT-NC displays a good gravimetric capacitance of 160 F/g at 0.5 A/g combing with outstanding capacitance retention of 90% at an extremely high current density of 100 A/g in acid electrolyte.Furthermore,a good energy density of 30 Wh/kg can be obtained in the organic electrolyte.

Strain- and twist-engineered optical absorption of few-layer black phosphorus

Density functional and many-body perturbation theories calculations were carried out to investigate fundamental and optical bandgap, exciton binding energy and optical absorption property of normal and strain- and twist-engineered few-layer black phosphorus （BP）. We found that the fundamental bandgaps of few layer BP can be engineered by layer stacking and in-plane strain, with linear relationships to their associated exciton binding energies. The strain-dependent optical absorption behaviors are also anisotropic that the position of the first absorption peak monotonically blue-shifts as the strain applies to either direction for incident light polarized along the armchair direction, but this is not the case for that along the zigzag direction. Given those striking properties, we proposed two prototype devices for building potentially more balanced light absorbers and light filter passes, which promotes further applications and investigations of BP in nanoelectronics and optoelectronics.

Identifi cation of Molecular Flipping of an Asymmetric Tris(phthalocyaninato)Lutetium Triple-Decker Complex by Scanning Tunneling Microscopy/Spectroscopy

The assembling behavior and electronic properties of asymmetric tris(phthalocyaninato)lutetium triple-decker sandwich complex molecules(Lu2Pc3)on highly oriented pyrolytic graphite(HOPG)surfaces have been studied by scanning tunneling microscopy/spectroscopy(STM/STS)methods.Phase transitions were observed at different bias polarities,involving an ordered packing arrangement with fourfold symmetry at negative bias and an amorphous arrangement at positive bias.Molecular switching behaviour for individual Lu2Pc3 molecules was reported here according to the bias-polarity-induced flipping phenomena and the peak shift in dI/dV versus V curves at different voltage scanning directions.The sensitive response of the strong intrinsic molecular dipole to an external electric field is proposed to be responsible for molecular switching of Lu_(2)Pc_(3)at the solid/liquid interface.

Highly pressure-sensitive graphene sponge fabricated by γ-ray irradiation reduction

Graphene sponge(GS) with microscale size, high mechanical elasticity and electrical conductivity has attracted great interest as a sensing material for piezoresistive pressure sensor. However, GS offering a lower limit of pressure detection with high gauge factor, which is closely dependent on the mechanical and electrical properties and determined by the fabrication process, is still demanded. Here, γ-ray irradiation reduced GS is reported to possess a gauge factor of 1.03 kPa^–1 with pressure detection limit of 10 Pa and high stress retention of 76% after 800 cycles of compressing/relaxation at strain of 50%. Compared with the carbon nanotube(CNT) reinforced GS, the improved lower limit of pressure detection and gauge factor of the GS prepared by γ-ray irradiation is due to the low compression stress(0.9 kPa at stain of 50%). These excellent physical properties of the GS are ascribed to the mild,residual free, and controllable reduction process offered by γ-ray irradiation.

Electronic structure of aqueous two-dimensional photocatalyst

The electronic structure,in particular the band edge position,of photocatalyst in presence of water is critical for photocatalytic water splitting.We propose a direct and systematic density functional theory(DFT)scheme to quantitatively predict band edge shifts and their microscopic origins for aqueous 2D photocatalyst,where thousands of atoms or more are able to be involved.This scheme is indispensable to correctly calculate the electronic structure of 2D photocatalyst in the presence of water,which is demonstrated in aqueous MoS_(2),GaS,InSe,GaSe and InS.It is found that the band edge of 2D photocatalysts are not rigidly shifted due to water as reported in previous studies of aqueous systems.Specifically,the CBM shift is quantitatively explained by geometric deformation,water dipole and charge redistribution effect while the fourth effect,i.e.,interfacial chemical contact,is revealed in the VBM shift.Moreover,the revealed upshift of CBM in aqueous MoS2 should thermodynamically help carriers to participate in hydrogen evolution reaction(HER),which underpin the reported experimental findings that MoS2 is an efficient HER photocatalyst.Our work paves the way to design 2D materials in general as low-cost and high-efficiency photocatalysts.