M-N3 Configuration on Boron Nitride Boosts Singlet Oxygen Generation via Peroxymonosulfate Activation for Selective Oxidation.

Singlet oxygen (1O2) is an essential reactive species responsible for selective oxidation of organic matter, especially in Fenton-like processes. However, due to the great limitations in synthesizing catalysts with well-defined active sites, the controllable production and practical application of 1O2 remain challenging. Herein, guided by theoretical simulations, a series of boron nitride-based single-atom catalysts (BvBN/M, M = Co, Fe, Cu, Ni and Mn) were synthesized to regulate 1O2 generation by activating peroxymonosulfate (PMS). All the fabricated BvBN/M catalysts with explicit M-N3 sites promoted the self-decomposition of the two PMS molecules to generate 1O2 with high selectivity, where BvBN/Co possessed moderate adsorption energy and d-band center exhibited superior catalytic activity. As an outcome, the BvBN/Co-PMS system coupled with membrane filtration technology could continuously transform aromatic alcohols to aldehydes with nearly 100% selectivity and conversion rate under mild conditions, suggesting the potential of this novel catalytic system for green organic synthesis.

Separation and reutilization of heavy metal ions in wastewater assisted by p-BN adsorbent.

Extracting heavy metal ions from wastewater has significant implications for both environmental remediation and resource preservation. However, the conventional adsorbents still suffer from incomplete ion removal and low utilization efficiency of the recovered metals. Herein, we present an extraction and reutilization method assisted by porous boron nitride (p-BN) containing high-density N atoms for metal recovery with simultaneous catalyst formation. The p-BN exhibits stable and efficient metal adsorption performance, particularly for ultra-trace-level water purification. The distribution coefficients towards Pb2+, Cd2+, Co2+ and Fe3+ can exceed 106 mL g-1 and the residual concentrations that reduced from 1 mg L-1 to 0.8-1.3 µg L-1 are much lower than the acceptable limits in drinking water standards of World Health Organization. Meanwhile, the used p-BN after Co ion adsorption can be directly adopted as a high-efficiency catalyst for activating peroxymonosulfate (PMS) in organic pollutant degradation without additional post-treatment, avoiding the secondary metal pollution and the problems of neglected manpower and energy consumption. Moreover, a flow-through multistage utilization system assisted by p-BN/polyvinylidene fluoride (PVDF) membrane is constructed for achieving both metal ion separation and reutilization in the removal of organic pollutants, providing a new avenue for sustainable wastewater remediation.

Intrinsic edge states and strain-tunable spin textures in the Janus 1T-VTeCl monolayer.

Using first-principles calculations and micro-magnetic simulations, we investigate the electronic structures, the effect of biaxial strain on the topological characteristics, magnetic anisotropy energy (MAE), Dzyaloshinskii-Moriya interaction (DMI) and spin textures in the Janus 1T phase VTeCl (1T-VTeCl) monolayer. Our results show that 1T-VTeCl has an intrinsic edge state, and a topological phase transition with a sizeable band gap is achieved by applying biaxial strain. Interestingly, the MAE can be switched from the in-plane to the off-plane with a compressive strain of -5%. Microscopically, the origin of MAE is mainly associated with the large spin-orbit coupling (SOC) from the heavy nonmagnetic Te atoms rather than that from the V atoms. Furthermore, the induced DMI (0.09 meV) can occur stabilizing magnetic merons without applying temperatures and magnetic fields. Then, the skyrmions, frustrated antiferromagnetism and vortex are induced after applying a suitable compressive strain. Our study provides compelling evidence that the 1T-VTeCl monolayer with topological properties holds great potential for application in spintronic devices, as well as information storage devices based on different magnetic phases achievable through strain engineering.

Low-Cost Preparation of High-Performance Na-B-H-S Electrolyte for All-Solid-State Sodium-Ion Batteries.

All-solid-state sodium-ion batteries have the potential to improve safety and mitigate the cost bottlenecks of the current lithium-ion battery system if a high-performance electrolyte with cost advantages can be easily synthesized. In this study, a one-step dehydrogenation-assisted strategy to synthesize the novel thio-borohydride (Na-B-H-S) electrolyte is proposed, in which both raw material cost and preparation temperature are significantly reduced. By using sodium borohydride (NaBH4 ) instead of B as a starting material, B atoms can be readily released from NaBH4 with much less energy and thus became more available to generate thio-borohydride. The synthesized Na-B-H-S (NaBH4 /Na-B-S) electrolyte exhibits excellent compatibility with current cathode materials, including FeF3 (1.0-4.5 V), Na3 V2 (PO4 )3 (2.0-4.0 V), and S (1.2-2.8 V). This novel Na-B-H-S electrolyte will take a place in mainstream electrolytes because of its advantages in preparation, cost, and compatibility with various cathode materials.

Electronic properties, skyrmions and bimerons in Janus CrXY (X, Y = S, Se, Te, Cl, Br, I, and X ≠ Y) monolayers.

Using first-principles calculations, we systematically investigate the electronic properties, chiral skyrmions and bimerons in two-dimensional (2D) Janus CrXY (X, Y = S, Se, Te, Cl, Br, I, and X ≠ Y) monolayers. We found that the categories of nonmagnetic atoms (X and Y in CrXY) determine whether CrXY is a ferromagnetic metal or a semiconductor. Unexpectedly, the CrBrS monolayer of these CrXY materials is a room temperature ferromagnetic semiconductor with a Curie temperature of 303 K, and it possesses an off-plane magnetic anisotropy energy of 0.06 meV. Besides, a strong Dzyaloshinskii-Moriya interaction (DMI) of 3.10 meV is found in CrTeI and is mainly induced by the strong spin-orbit coupling of the nonmagnetic atoms Te(I) rather than that of the magnetic Cr atoms. Furthermore, using micromagnetic simulations, skyrmions can be stabilized in CrSeBr without external magnetic fields. More importantly, the bimerons in CrSeCl with in-plane magnetic anisotropy can be transformed into skyrmions or a ferromagnetic state by controlling the direction of external magnetic fields. Our work investigates fourteen kinds of Janus monolayers, serving as guidelines for materials research on DMI, skyrmions and bimerons.

Construction of Co/FeCo@Fe(Co)3O4 heterojunction rich in oxygen vacancies derived from metal-organic frameworks using O2 plasma as a high-performance bifunctional catalyst for rechargeable zinc-air batteries.

Developing high-efficient, good-durability, and low-cost bifunctional non-precious metal catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is urgent and significant for promoting the practical rechargeable zinc-air batteries (RZABs). Herein, N-doped carbon coated Co/FeCo@Fe(Co)3O4 heterojunction rich in oxygen vacancies derived from metal-organic frameworks (MOFs) is successfully constructed by O2 plasma treatment. The phase transition of Co/FeCo to FeCo oxide (Fe3O4/Co3O4) mainly occurs on the surface of nanoparticles (NPs) during the O2 plasma treatment, which can form rich oxygen vacancies simultaneously. The fabricated catalyst P-Co3Fe1/NC-700-10 with optimal O2 plasma treatment time of 10 min can reduce the potential gap between the OER and ORR to 760 mV, which is much lower than commercial 20% Pt/C + RuO2 (910 mV). Density functional theory (DFT) calculation indicates that the synergistic coupling between Co/FeCo alloy NPs and FeCo oxide layer can promote the ORR/OER performance. Both liquid electrolyte RZAB and flexible all-solid-state RZAB using P-Co3Fe1/NC-700-10 as the air-cathode catalyst display high power density, specific capacity and excellent stability. This work provides an effective idea for the development of high performance bifunctional electrocatalyst and the application of RZABs.

Strain-induced magnetic phase transition, magnetic anisotropy switching and bilayer antiferromagnetic skyrmions in van der Waals magnet CrTe2.

In recent years, considerable attention has been paid to the research of peculiar magnetism in two-dimensional (2D) van der Waals (vdW) layered materials. Here, we unveil the major features and deep physical mechanisms of a magnetic phase transition and magnetic anisotropy switching in monolayer CrTe2 and antiferromagnetic (AFM) skyrmions in bilayer CrTe2via first-principles calculations and micromagnetic simulations. We find that a magnetic phase transition from stripy-type AFM to ferromagnetic (FM) order can be induced by applying a tensile strain of 3%. More interestingly, the magnetic easy axis can be switched between in-plane and off-plane via adjusting the magnitude of strain. Besides, the topologically protected bilayer AFM skyrmion is stabilized by a large Dzyaloshinskii-Moriya interaction (DMI) of 1.43 meV and a skyrmion lattice can be induced by a magnetic field of 6.9 T at 100 K. Different from the monolayer magnetic skyrmion, the bilayer AFM skyrmion is more promising in spintronic nanodevices owing to the suppressed skyrmion Hall effect. Our findings clarify the underlying mechanisms of the strain-tunable magnetic phase transition, magnetic anisotropy switching and bilayer AFM skyrmions in vdW magnet CrTe2, and also highlight the promising applications of CrTe2 in next-generation information storage devices.

Topological phase transition and skyrmions in a Janus MnSbBiSe2Te2 monolayer.

Using first-principles calculations and micro-magnetic simulations, we propose a Janus MnSbBiSe2Te2 (MSBST) monolayer derived from the MnBi2Te4 (MBT) ferromagnet and investigate the influence of biaxial strain on the electronic structures, topological characteristics and spin textures. Different from pristine MBT with an out-of-plane easy axis, the anisotropy of MSBST prefers an in-plane direction. Intriguingly, switching the easy axis direction of MSBST will significantly modify the band structure. Topological phase transition can be achieved by applying a compressive strain, making MSBST become a topological insulator with . Moreover, due to the inherent inversion asymmetry of Janus MSBST, a large Dzyaloshinskii-Moriya interaction (DMI) is induced for generating and stabilizing skyrmions. By micro-magnetic simulations, the results of spin textures show that the skyrmions phase can be achieved in MSBST with an external magnetic field of 0.8 T. Our findings provide guidelines for the development and application of spintronic devices with nontrivial topological properties and a large DMI.

Spontaneous magnetic merons in a half-metallic Mn2I3Br3 monolayer with easy-plane anisotropy.

In recent years, great effort has been made in the study of two-dimensional (2D) van der Waals ferromagnets that can stabilize peculiar chiral spin textures, such as magnetic skyrmions and merons. Here, by first-principles calculations and micromagnetic simulations, we systematically investigate the in-plane magnetic anisotropy, Dzyaloshinskii-Moriya interaction (DMI) and magnetic merons in a Mn2I3Br3 monolayer. Mn2I3Br3 exhibits half-metallic behavior with a large band gap (∼2.7 eV) for spin-down electrons, but is gapless for spin-up ones. In addition, unlike most 2D ferromagnets with an off-plane magnetic easy axis and negligible DMI, the magnetic easy axis of Mn2I3Br3 is in-plane, with a large magnetic anisotropy energy of -13.2 meV and a strong DMI of 4.6 meV, which are mainly induced by the strong spin-orbital coupling of I atoms, microscopically. In particular, spontaneous magnetic merons, stabilized by the DMI, can exist in a wide magnetic field range (0-6 T). Our work not only provides important guidelines for the investigation of the DMI and merons in half-metallic materials, but also demonstrates the Mn2I3Br3 monolayer as an ideal platform to explore the deep physics of magnetic merons and as a promising candidate for magnetic storage devices, as well as spin filters.

N-Doped Carbon Nanotubes Derived from Graphene Oxide with Embedment of FeCo Nanoparticles as Bifunctional Air Electrode for Rechargeable Liquid and Flexible All-Solid-State Zinc-Air Batteries.

This work reports a novel approach for the synthesis of FeCo alloy nanoparticles (NPs) embedded in the N,P-codoped carbon coated nitrogen-doped carbon nanotubes (NPC/FeCo@NCNTs). Specifically, the synthesis of NCNT is achieved by the calcination of graphene oxide-coated polystyrene spheres with Fe3+, Co2+ and melamine adsorbed, during which graphene oxide is transformed into carbon nanotubes and simultaneously nitrogen is doped into the graphitic structure. The NPC/FeCo@NCNT is demonstrated to be an efficient and durable bifunctional catalyst for oxygen evolution (OER) and oxygen reduction reaction (ORR). It only needs an overpotential of 339.5 mV to deliver 10 mA cm-2 for OER and an onset potential of 0.92 V to drive ORR. Its bifunctional catalytic activities outperform those of the composite catalyst Pt/C + RuO2 and most bifunctional catalysts reported. The experimental results and density functional theory calculations have demonstrated that the interplay between FeCo NPs and NCNT and the presence of N,P-codoped carbon structure play important roles in increasing the catalytic activities of the NPC/FeCo@NCNT. More impressively, the NPC/FeCo@NCNT can be used as the air-electrode catalyst, improving the performance of rechargeable liquid and flexible all-solid-state zinc-air batteries.

Cation Exchange Enabled Cu Dopants Location Tailoring and Photoelectric Properties Regulation in CdS Nanosheets.

Doping-related point defect engineering in low-dimensional semiconductor nanostructures is important to regulate their optical and electronic properties. The substitutional or interstitial location of heterovalent dopants is critical and has not been controlled effectively yet. Herein, we carefully control the kinetics of reverse cation exchange between CuxS 2D nanosheets and ligand-coordinated Cd2+ cations to control the Cu doping sites in CdS nanosheets (NSs). The substitutional and interstitial Cu dopants were directly confirmed by spherical aberration-corrected TEM (SACTEM) and their X-ray absorption spectroscopy (XAS) coordination investigation. Density functional theory (DFT) calculations and their experimental conductivities and dopant luminescence performance demonstrated the dramatic differences that are due to the location of different Cu dopants. These findings provide deeper insights on dopants' location regulation in a nanostructured host semiconductor.

Solvent-Induced Growth of Free-Standing 2D Si Nanosheets.

2D Si nanomaterials draw great interest owing to their fascinating properties and potential applications in electronic devices, catalysts, and energy storage and conversion devices. However, high-quality and large-scale synthesis of Si nanosheets remains a big challenge, despite the limited reports on their preparations via chemical exfoliation of layered Zintl silicide, magnesiothermic reduction of layered silicon oxide, and chemical vapor deposition. In this work, a facile, solution method to produce free-standing Si nanosheets in high yields and low cost, based on the reaction of commercial magnesium powder with trichlorosilane and tripropylamine in dichloromethane under mild conditions, is reported. The prepared Si nanosheets have an average thickness of ≈2 nm and show photoluminescence. Experiments demonstrate that the key to the formation of Si nanosheets is the use of dichloromethane as a solvent. This method can be used to prepare Si nanosheets in large scale for various potential applications and possibly Si crystals with specific crystal morphology.

Mulberry-Inspired Nickel-Niobium Phosphide on Plasma-Defect-Engineered Carbon Support for High-Performance Hydrogen Evolution.

Bimetallic phosphate electrocatalysts on carbon-cloth support are among the most promising industry-relevant solutions for electrocatalytic hydrogen production. To address the persistent issue of hetero-phase interfacing on carbon support while ensuring high activity and stability, a low-cost, high-performance hydrogen evolution reaction (HER) electrocatalyst is developed. Bi-phase Ni12 P5 -Ni4 Nb5 P4 nanocrystals with rich heterointerfaces and phase edges are successfully fabricated on carbon cloth (CC), which is enabled by intentional defect creation by atmospheric pressure dielectric barrier discharge (DBD) plasma (PCC). The obtained Ni12 P5 -Ni4 Nb5 P4 /PCC electrocatalyst exhibits excellent HER performance, heralded by the low overpotentials of 81 and 287 mV for delivering current densities of 10 (j10 ) and 500 (j500 ) mA cm-2 , respectively. Meanwhile, the Ni12 P5 -Ni4 Nb5 P4 /PCC maintains spectacular catalytic activity at high current density region (>j615 ), which outperformed the industry-relevant benchmark Pt/C/PCC catalyst. The catalyst grown on the plasma-treated support shows remarkably longer operation and ultra-stable electrocatalytic characteristics over 100 h continuous operation. Ab initio numerical simulations reveal that Ni atoms exposed in the heterointerfaces act as the main catalytically active centers for HER.

One-pot solution synthesis of carbon-coated silicon nanoparticles as an anode material for lithium-ion batteries.

Carbon-coated silicon nanoparticles were in situ synthesized via a facile one-pot solution synthesis method, which delivered an excellent cycling performance with a retained discharge capacity of 1120 mA h g-1 and almost no capacity decay after 500 cycles at 2 A g-1 when evaluated as an anode material in lithium ion batteries.

Proximity exchange induced gap opening and topological feature in graphene/1T'-MX2 (M = Mo,W; X = S,Se,Te) Dirac heterostructures.

By using first-principles calculations, we demonstrate the influence of proximity effect on the band structures of heterostructures formed by graphene stacking on a two dimensional (2D) topological insulator (TI) 1T'-MX2. The interlayer distance d between graphene and TI decreases with the enhancement of the intrinsic lattice anisotropy of 1T'-MX2, which determines different strength of the interlayer proximity interaction. The bandgap can be opened by the proximity exchange. The weak anisotropic symmetry of heterostructure (large d) only results in a small band gap (∼50 meV) in graphene/MoTe2. However, a large energy gap (up to ∼200 meV) can be obtained in graphene/MoS2, which is attributed to the inter-intralayer charge transfer due to the strong proximity interaction of the hetero-interface (small d). In addition, the 1T'-MX2 of heterostructure still possesses the topological feature of Z 2 = 1, since the graphene has a negligible effect on the band structure of the system.

p-n junction induced electron injection type transparent photosensitive film of Cu2O/carbon quantum dots/ZnO.

An electron injection type transparent photosensitive Cu2O/carbon quantum dot (C QD)/ZnO p-n junction film was prepared by a simple route in which, successively, the ZnO film was prepared by a sputtering process, the C QDs and Cu2O were prepared by hydrothermal synthetic and chemical methods, then the C QDs and Cu2O were introduced onto the surface of the ZnO film. The results indicated that the C QDs and Cu2O were well combined with the ZnO film. The transparency and photosensitivity of this film were investigated, and exhibited an obvious photosensitive enhancement compared with those of the unmodified film. Through analysis, this enhancement of the photoconductivity could be attributed to the remarkable Cu2O/ZnO p-n junction and C QDs with unique up-converted photoluminescence.

Effects of Iron Doping on the Physical Properties of Quaternary Ferromagnetic Sulfide: Ba2Fe0.6V1.4S6.

The mixed-metal sulfide compound with the formula Ba2Fe0.6V1.4S6 was successfully synthesized via solid-state reaction. Ba2Fe0.6V1.4S6 has a quasi-one-dimensional structure and crystallizes in the hexagonal space group P63/mmc. The structure is composed of face-sharing anion octahedron [MS6]8- (M = V or Fe) units to construct infinite chains along the c axis, in which the Fe atoms randomly occupy the V sites. The Ba2+ ions reside between adjacent chains. Magnetic susceptibility measurements reveal a transition between paramagnetism and ferromagnetism around 25 K. The small polaron hopping (SPH) conduction behavior has been observed in the higher temperature region (75-300 K), while in the lower temperature region (25-74 K), the resistivity features a variable range hopping mechanism (VRH). The analysis of density of states indicates that Fe-3dz2 and S-3p states mainly dominate the valence band maximum, while Fe-3dz2 states contribute significantly to the magnetic susceptibility.

Enhanced Superconductivity in Restacked TaS2 Nanosheets.

Since interface superconductivity was discovered at the interface between two insulating layers LaAlO3 and SrTiO3, such interface-induced superconducting systems have been a research hotspot in superconductivity. Here, we report homogeneous interfaces formed by stacking chemically exfoliated monolayer TaS2 nanosheets randomly. Enhanced superconductivity of Tc = 3 K is observed, compared with 0.8 K of parent 2H-TaS2. The measurement of heat capacity shows the increase of electronic specific-heat coefficient γ of restacked TaS2 nanosheets compared to parent 2H-TaS2 crystals. Density functional theory calculations indicate that increase and delocalization of electron states near the Fermi surface due to the homogeneous interfaces effects could account for the enhanced superconductivity.

Dynamics of analytical three-dimensional solutions in Bose-Einstein condensates with time-dependent gain and potential.

Using the F-expansion method we systematically present exact solutions of the three-dimensional nonlinear generalized Gross-Pitaevskii equation, with time-varying gain or loss, in both attractive and expulsive harmonic confinement regimes. This approach allows us to obtain solitons for a large variety of solutions depending on the time-varying potential and the gain or loss profiles. The dynamics of these matter waves, including quasibreathing solitons, double-quasibreathing solitons, and three-quasibreathing solitons, is discussed. The explicit functions that describe the evolution of the amplitude, width, and trajectory of the soliton's wave center are presented exactly. It is demonstrated that an arbitrary additional time-dependent gain function can be added to the model to control the amplitude and width of the soliton and the nonlinearity without affecting the motion of the solitons' wave center. Additionally, a number of exact traveling waves, including the Faraday pattern formation, have been found. The obtained results may raise the possibility of relative experiments and potential applications.