Two-dimensional MgSiP_2 with anisotropic electronic properties and good performances for Na-ion batteries

Using the global particle-swarm optimization method and density functional theory,we predict a new stable two-dimensional layered material:MgSiP_2 with a low-buckled honeycomb lattice.Our HSE06 calculation shows that MgSiP_2 is an indirect-gap semiconductor with a band-gap of 1.20 eV,closed to that of bulk silicon.More remarkably,MgSiP2 exhibits worthwhile anisotropy along with electron and hole carrier mobility.A ultrahigh electron mobility is even up to 1.29 × 104 cm~2 V ~1 s ~1.while the hole mobility is nearly zero along the a direction.The large difference of the mobility between electron and hole together with the suitable band-gap suggest that MgSiP_2 may be a good candidate for solar cell or photochemical catalysis material.Furthermore,we explore MgSiP2 as an anode for sodium-ion batte ries.Upon Na adsorption,the semiconducting MgSiP2 transforms to a metallic state,ensuring good electrical conductivity.A maximum theoretical capacity of 1406 mAh/g,a small volume change(within 9.5%),a small diffusion barrier(～0.16 eV) and low average open-circuit voltages(～0.15 V) were found fo r MgSiP2 as an anode for sodium-ion batteries.These results are helpful to deepen the understanding of MgSiP2 as a nanoelectronic device and a potential anode for Na-ion batteries.     

Prediction of stable BC3N2 monolayer from first-principles calculations: Stoichiometry,crystal structure,electronic and adsorption properties

In this paper, a novel BC₃N₂ monolayer has been found with a graphene-like structure using the developed particle swarm optimization algorithm in combination with ab initio calculations. The predicted structure meets the thermodynamical, dynamical, and mechanical stability requirements. Interestingly, the BC₃N₂ plane shows a metallic character. Importantly, BC₃N₂ has an in-plane stiffness comparable to that of graphene. We have also investigated the adsorption characteristics of CO₂ on pristine monolayer and Mo functionalized monolayer using density functional theory. Subsequently, electronic structures of the interacting systems (CO₂ molecule and substrates) have been preliminarily explored. The results show that Mo/BC₃N₂ has a stronger adsorption capacity towards CO₂ comparing with the pristine one, which can provide a reference for the further study of the CO₂ reduction mechanism on the transition metal-functionalized surface as well as the new catalyst’s design.     

二硫化锡纳米片阻变存储器的制备与性能

采用水热法合成了尺寸为50~100 nm的二硫化锡纳米片,并首次以二硫化锡作为阻变层材料的阻变存储器（Cu/PMMA/SnS₂/Ag,PMMA=聚甲基丙烯酸甲酯）,对其阻变性能进行了研究。结果表明： Cu/PMMA/SnS₂/Ag阻变存储器的开关比约10⁵,耐受性2.7×10³。在上述2项性能指标达到较优水平的同时,开态与关态电压分别仅约为0.28与-0.19 V。     

Associative vs. dissociative mechanism: Electrocatalysis of nitric oxide to ammonia

Nitric oxide reduction to ammonia by electrocatalysis is the potential application in the elimination of smog and energy conversion. In this work, the feasibility of the application of two-dimensional metal borides(MBenes) in nitric oxide electroreduction reaction(NOER) was investigated through density functional theory calculations. Including the geometry and electronic structure of five kinds of MBenes, the adsorption of NO on the surface of these substrates, the selective adsorption of hydrog...     

Predicted a honeycomb metallic BiC and a direct semiconducting Bi2C monolayer as excellent CO2 adsorbents

We predicted two stable two-dimensional materials of carbon and bismuth elements, namely BiC and Bi₂C monolayers. The stabilities of two monolayers were examined by cohesive energy, Born criteria, firstprinciple MD simulations and phonon spectra, respectively. By including the spin-orbit coupling effects,the Bi C monolayer is a metal and the Bi₂C monolayer possesses a narrow direct（indirect） band gap of 0.403（0.126） e V under the HSE06（GGA-PBE） functional. For the adsorptio...     

Synthesis and properties of polylactide terpolymers P(LLA‐TMC‐GA) catalyzed by zirconium (IV) acetylacetonate

A series of L‐lactide (LLA), 1,3‐trimethylene carbonate (TMC) and glycolide (GA) terpolymers (LTG) of different monomer molar ratios were synthesized by using ring‐opening copolymerization. An effective and low‐toxic zirconium (IV) acetylacetonate Zr(Acac)₄ was used as catalyst. The viscosity‐average molecular weights (M_η) of obtained polymers were all above 2.2×10⁴ g/mol. The chemical structure and viscosity of terpolymers were confirmed by Fourier transform infrared spectroscopy (FTIR), ¹H nuclear magnetic resonance (¹HNMR), ¹³C nuclear magnetic resonance (¹³CNMR) and an Ubbelohde viscometer. The thermal and mechanical properties were investigated by means of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) and stress‐strain measurements. Results suggested that all terpolymers were amorphous and showed good thermal stability. Also it was found that elongation increased with the decreasing of LLA unit. More importantly, terpolymers displayed shape memory property when deformation temperatures were 14‐15 °C above T_g.     

Nonlinear softening and hardening nonlocal bending stiffness of an initially curved monolayer graphene

In the present article, the governing nonlinear nonlocal elastic equations are obtained for a monolayer graphene with an initial curvature and the related softening and hardening bending stiffness is analytically calculated. The effects of large deformation, initial curvature, discreteness and direction of chiral vector on the bending stiffness of the monolayer graphene are discussed in detail. A behavior more complex than previously reported in the literature emerges. It is found that the bending stiffness of graphene strongly depends on the initial configuration, showing not obvious maxima and minima, and suggesting the possibility of a smart tuning.     

In-situ growth of V2O5 flower-like structures on ceramic tubes and their trimethylamine sensing properties

V₂O₅ flower-like structures assembled by thin nanosheets were in-situ growth on ceramic tubes by hydrothermal process. The structural characterization indicates that V₂O₅ flower-like structures is orthogonal diamond phase, which entirely covered on the surface of ceramic tubes. TMA sensing measured results revealed that the sensor based on V₂O₅ flower-like structures exhibited fast reversible and response, good selectivity to TMA and good stability at 200 °C. The good sensing performance may be ascribed to flower-like structures and directly growth sensing film on the ceramic tube without structure damage. Our works give a simple in-situ growth flower-like structures route on sensing device, which exhibits potential application for detecting trace amounts of TMA gas.     

Two-dimensional 1T-PS2 as a promising anode material for sodium-ion batteries with ultra-high capacity,low average voltage and appropriate mobility

As electrodes, two-dimensional materials show special advantages including the infinite planar lengths, broad electrochemical window, large surface–volume ratio, and much exposed active sites. In theory, the two-dimensional materials consist of the elements with high electronegativity may absorb more Na atoms, resulting in a high battery storage capacity. Based on the above idea, we selected the two dimensional metallic PS₂ with 1T-Type structure as an anode material, and explored its potential applications as an electrode material for Na-ion battery through first-principle calculations. As we expected, when two dimensional PS₂ is used as an anode in Na-ion battery, it can adsorb maximum three layers of sodium atoms on both sides of the monolayer, resulting in a maximum theoretical capacity of 1692 mAh/g. Furthermore, it also possesses a rather small sodium diffusion barrier of 0.17 eV, a low average open-circuit voltage of 0.18 V, and a relatively small lattice changes within 13% during the intercalation of Na. These results suggested that the two dimensional PS₂ is a potentially excellent Na-ion battery anode. Our idea of designing two-dimensional anode materials with high storage capacity may provide some references for designing the next generation anode materials of metal-ion batteries.     

Enhanced alcohol and H2O adsorption and separation performances by introducing pyridyl ligand in a MOF

MOFs (Metal-Organic Framework), as promising crystalline materials of adsorption and separation, has been the subject of many recent investigations. However, the H₂O stability of MOFs and the variation of adsorption selectivity in humid environments largely hinder attempts as excellent adsorbents in numerous scenarios. This study employs hydro-thermal synthesis [Cd_0.5(DPETA)_0.5]_n using 2,3′,5,5′-Diphenyl tetracarboxylic acid (DPETA) and Cd(NO₃)₂·4H₂O as ligands and metal ions, respectively. And it is modified by adding auxiliary ligands 4-4′-bipyridyl (bpy) and 1,2-bis (4-pyridyl) ethylene(bpe) to obtain [Cd_1.5bpy₂(DPETA)]_n and [Cd₂bpe₂(DPETA)]_n.The phase purity of the MOFs is examined using PXRD and FT-IR spectrum. The adsorption capacities of three MOFs are tested separately for water, ethanol and methanol using vapor adsorption. Their adsorption conformations and hydrogen bond lengths are also calculated by the GCMC method. The adsorption selection ratios of methanol and ethanol are deduced in combination with the IAST method under three components of water, methanol and ethanol. The results shows a methanol/ethanol adsorption separation ratio of 45 for [Cd_1.5bpy₂(DPETA)]_n at 297 K, which is consistent with the of GCMC demonstrated. These results suggest that the methanol/ethanol adsorption selectivity ratio can be improved by increasing the adsorption force on methanol through by adding of auxiliary pyridyl ethylene. It can be used for efficient methanol/ethanol separation in humid environments.