Identification and comparison of the local physicochemical structures of transition metal-based layered double hydroxides for high performance electrochemical oxygen evolution reactions

Layered double hydroxides(LDHs) have attracted considerable attention as a cost effective alternative to the precious iridium-and ruthenium-based electrocatalysts for an oxygen evolution reaction(OER),a bottleneck of water electrolysis for sustainable hydrogen production.Despite their excellent OER performance,the structural and electronic properties of LDHs,particularly during the OER process,remain to be poorly understood.In this study,a series of LDH catalysts is investigated through in situ X-ray absorption fine structure analyses and density functional theory(DFT) calculations.Our experimental results reveal that the LDH catalyst with equal amounts of Ni and Fe(NF-LDH) exhibits the highest OER activity and catalytic life span when compared with its counterparts having equal amounts of Ni and Co(NC-LDH)and Ni only(Ni-LDH).The NF-LDH shows a markedly enhanced OER kinetics compared to the NC-LDH and the Ni-LDH,as proven by the lower overpotentials of 180,240,and 310 mV,respectively,and the Tafel slopes of 35.1,43.4,and 62.7 mV dec^(-1),respectively.The DFT calculations demonstrate that the lowest overpotential of the NF-LDH is associated with the active sites located at the edge planes of NF-LDH in contrast to those located at the basal planes of Ni-LDH and NC-LDH.The current study pinpoints the active sites on various LDHs and presents strategies for optimizing the OER performance of the LDH catalysts.

Smart Interfacing between Co-Fe Layered Double Hydroxide and Graphitic Carbon Nitride for High-efficiency Electrocatalytic Nitrogen Reduction

Bimetallic compounds such as hydrotalcite-type layered double hydroxides(LDHs)are promising electrocatalysts owing to their unique electronic structures.However,their abilities toward nitrogen adsorption and reduction are undermined since the surface-mantled,electronegative-OH groups hinder the charge transfer between transition metal atoms and nitrogen molecules.Herein,a smart interfacing strategy is proposed to construct a coupled heterointerface between LDH and 2D g-C_(3)N_(4),which is proven by density functional theory(DFT)investigations to be favorable for nitrogen adsorption and ammonia desorption compared with neat LDH surface.The interfaced LDH and g-C_(3)N_(4) is further hybridized with a self-standing TiO_(2) nanofibrous membrane(NM)to maximize the interfacial effect owing to its high porosity and large surface area.Profited from the synergistic superiorities of the three components,the LDH@C_(3)N_(4)@TiO_(2) NM delivers superior ammonia yield(2.07×10^(−9) mol s^(−1) cm^(−2))and Faradaic efficiency(25.3%),making it a high-efficiency,noble-metal-free catalyst system toward electrocatalytic nitrogen reduction.

Development of mean-field electrical double layer theory

In order to understand the electric interfacial behavior, mean field based electric double layer （EDL） theory has been continuously developed over the past 150 years. In this article, we briefly review the development of the EDL model, from the dimensionless Gouy-Chapman model to the symmetric Bikerman-Freise model, and finally toward size-asymmetric mean field theory models. We provide the general derivations within the framework of Helmholtz free energy of the lattice- gas model, and it can be seen that the above-mentioned models are consistent in the sense that the interconversi0n among them can be achieved by reducing the basic assumptions.

Mechanical analysis of double-layered circular graphene sheets as building material embedded in an elastic medium

Possessing the unique and highly valuable properties, graphene sheets(GSs) have attracted increasing attention including that from the building engineer due to the fact that Graphene can be utilized to reinforce concrete and other building materials. In this work, the nonlocal elastic theory and classical plate theory(CLPT) are used to derive the governing equations. The element-free framework for analyzing the buckling behaviors of double layer circular graphene sheets(DLCGSs) relying on an elastic medium is proposed. Pasternak-type model is adopted to describe the elastic medium. Accordingly, the influences of boundary conditions, size of GSs and nonlocal parameters on the buckling behavior of DLCGSs are investigated. The results show that the OP buckling modes are only sensible to the van der Waals forces.

Study of the Electrical Double Layer of a Spherical Micelle: Functional Theoretical Approach

By using the iterative method in functional theory, an analytic expression of the Poisson-Boltzmann equation (PB eq.), which describes the distribution of the potential of electrical double layer of a spherical micelle, has been carried out under the general potential condition for the first time. The method also can give the radius, the surface potential, and the thickness of the layer.

Curvature effects on electric-double-layer capacitance

Understanding the microscopic structure and thermodynamic properties of electrode/electrolyte interfaces is central to the rational design of electric-double-layer capacitors(EDLCs).Whereas practical applications often entail electrodes with complicated pore structures,theoretical studies are mostly restricted to EDLCs of simple geometry such as planar or slit pores ignoring the curvature effects of the electrode surface.Significant gaps exist regarding the EDLC performance and the interfacial structure.Herein the classical density functional theory(CDFT)is used to study the capacitance and interfacial behavior of spherical electric double layers within a coarse-grained model.The capacitive performance is associated with electrode curvature,surface potential,and electrolyte concentration and can be correlated with a regression-tree(RT)model.The combination of CDFT with machine-learning methods provides a promising quantitative framework useful for the computational screening of porous electrodes and novel electrolytes.

Magnetic Properties of Ferromagnetic Double Layers with Ferrimagnetic Interlayer Coupling at Zero Temperature

纺纱波浪理论被用来磁性的夹层在零温度联合与含铁学习铁磁性的双层的磁性。纺纱波浪系列和四潜水艇格子磁化和内部精力被采用延迟的格林功能技术计算。以地面状态的潜水艇格子磁化比他们的古典价值小，由于旋转的零点的量变化。

Doping engineering of lithium-aluminum layered double hydroxides for high-efficiency lithium extraction from salt lake brines

Lithium-aluminum layered double hydroxides(LiAl-LDH)have been be successfully applied in commercial-scale for lithium extraction from salt lake brine,however,further advancement of their applications is hampered by suboptimal Li^(+)adsorption performance and ambiguous extraction process.Herein,a doping engineering strategy was developed to fabricate novel Zn^(2+)-doped LiAl-LDH(LiZnAl-LDH)with remarkable higher Li^(+)adsorption capacity(13.4 mg/g)and selectivity(separation factors of 213,834,171 for Li^(+)/K^(+),Li^(+)/Na^(+),Li^(+)/Mg^(2+),respectively),as well as lossless reusability in Luobupo brine compared to the pristine LiAl-LDH.Further,combining experiments and simulation calculations,it was revealed that the specific surface area,hydrophilic,and surface attraction for Li^(+)of LiZnAl-LDH were significantly improved,reducing the adsorption energy(Ead)and Gibbs free energy(ΔG),thus facilitating the transfer of Li^(+)from brine into interface followed by insertion into voids.Importantly,the intrinsic oxygen vacancies derived from Zn-doping depressed the diffusion energy barrier of Li^(+),which accelerated the diffusion process of Li^(+)in the internal bulk of LiZnAl-LDH.This work provides a general strategy to overcome the existing limitations of Li^(+)recovery and deepens the understanding of Li^(+)extraction on LiAl-LDH.

电动汽车锂电池组双层环形均衡器研究

传统Buck-Boost均衡电路传输路径长且均衡效率低,现有的环形均衡器无法从根本上解决该问题。针对该问题,文中提出了一种基于Buck-Boost及开关电容的锂电池双层环形均衡器。该均衡电路采用模块化均衡的方法在底层模块和顶层模块采用Buck-Boost和开关电容的混合电路实现均衡,并采用图论分析的方法,从均衡速度、均衡效率两方面分析电路结构。结果表明,该均衡电路具有能量传输路径少、能量传输效率高的优点。文中在MATLAB/Simulink电力仿真平台上搭建了均衡电路的仿真模型,仿真结果表明基于Buck-Boost及开关电容的双层环形均衡器比单层环形均衡器均衡速度提高了46%。文中搭建了4节电池的实验样机对环形均衡电路工作原理及系统均衡效率进行实验验证,结果表明双层环形均衡器比单层环形均衡器均衡效率可提高26.78%。仿真与实验结果与理论分析一致,说明电路结构合理有效。

假想防卫的学说检视与认定

假想防卫问题一直是刑法理论与实务存在争议的问题,我国传统理论对于假想防卫的认定存在说理论证不清晰的问题。通过对主要学说进行检视,认定法律效果转换之罪责说最为完善。我国存在改良的四要件理论与三阶层理论的前提,结合刑法第14条规定分析具备构建故意双重定位的空间,通过对“否定罪责故意后是否需要重新审查过失犯罪体系”与“构成要件故意+罪责过失成立故意犯或过失犯”问题的分析,认定解决假想防卫问题的路径为:行为人的行为满足构成要件符合性阶层,成立构成要件故意;不存在违法阻却事由因而进入罪责阶段成立罪责过失,最终成立故意犯的责任减等(减为过失);不存在过失则以意外事件处理。

Study on Interaction Between Two Parallel Plates with Iteration Method in Functional Theory

由介绍功能的理论进电的双层(EDL ) 的计算相互作用，二个平行盘子的相互作用精力在低、中等、高的潜力分别地是计算的。与二存在方法的结果相比， Debye-H 湲獥？

基于微分求积有限元法的双层微板系统振动特性研究

基于修正的偶应力理论和两变量精化的剪切变形理论,建立了由Winkler-Pasternak连续弹性夹层连接的双层微板系统的自由振动模型,着重推导了系统异步振动的运动微分方程和势能泛函。融合Gauss-Lobatto求积准则和微分求积准则构造了具有C~1连续性的微分求积有限元。通过与已有文献进行对比,验证了数值方法的有效性。详细讨论了各种因素对系统同步和异步振动特性的影响。结果表明,系统的自由振动特性对材料尺度参数、长宽比、长厚比以及边界条件呈现出依赖性;弹性夹层刚度仅对系统异步振动产生作用;随着模态阶次的增大,材料尺度参数和弹性夹层刚度对异步振动频率和模态的影响变得显著。

镍铁基层状双氢氧化物析氧反应研究进展

近年来,能源危机、环境污染等问题导致了人们对开发高效清洁能源的迫切需求。氢气作为一种具备广泛应用前景的可替代能源,可通过电解水制备。然而,电解水制氢过程主要受制于阳极缓慢的析氧反应(oxygen evolution reaction,OER)过程。镍铁基层状双氢氧化物(nickeliron layered double hydroxide,NiFe-LDH)由于其具备独特的层状结构、成本低廉、含量丰富且催化性能优异等特点,近年来被广泛研究。综述了通过晶格掺杂、空位缺陷和表面修饰对NiFeLDH化合物进行改性的最新研究进展,简要讨论了改性NiFe-LDH化合物研究过程中遇到的挑战和前景。

面内压缩荷载作用下双层微板系统的同步/异步屈曲

采用修正的偶应力理论和双变量高阶剪切变形理论,发展了层间填充弹性介质的双层微板系统在面内压缩荷载作用下的屈曲模型.基于Euler-Lagrange方程推导了系统屈曲的控制微分方程,运用Navier法获得了上下层均为四边简支时系统同步/异步屈曲的解析解.通过数值算例讨论了系统各参数对其屈曲特性的影响.结果表明:系统的异步屈曲特性依赖于材料尺度参数、长宽比和弹性介质模量,而同步屈曲特性仅依赖于前两项,并且异步屈曲荷载高于同步屈曲荷载;弹性介质的Pasternak模量较之于Winkler模量对系统的屈曲特性影响更显著.

弹体斜侵彻双层钢板的结构响应和失效研究

为探究弹体斜侵彻多层钢板的结构响应及失效规律,开展了圆形、椭圆和非对称椭圆三种截面弹体对双层钢板的斜侵彻试验,获得了不同弹体的弹道特性和结构失效情况。在此基础上,采用有限元软件对弹体斜侵彻过程的弹道特性、动态载荷以及结构响应进行了数值分析。基于空间自由梁理论和弹体动态载荷,给出了侵彻过程中弹体轴力和弯矩的分布规律,建立了弹体结构强度与失效分析方法。结果表明,弹体以正着角水平侵彻多层钢板时,存在一个临界攻角;当攻角小于临界值时,侵彻过程中会出现弹体低头、弹道向下偏转的现象;当攻角大于临界值时,则出现弹体抬头、弹道向上偏转的现象;该临界攻角随着靶板厚度的减小而增大。对于强度高、韧性低的弹体,失效模式为脆性断裂,断裂位置距头部0.72~0.81倍弹长,弹身后部所受横向冲击载荷是造成弹体断裂的主要原因。建立的弹体结构响应模型可准确预测弹体断裂失效及发生位置。此外,在三种截面弹体中,非对称椭圆弹体的断裂位置更接近头部。

双层均质耦合网络信息传播动力学研究

当前空间信息网络中各类系统越来越多,功能越发复杂,系统与系统之间连接也更加紧密。不同系统之间的链接可以看为多层网络之间的互联互通。研究双层均质耦合网络信息传播行为,揭示影响双层均质耦合网络信息传播的相关因素。首先,以未知状态(Susceptible)-已知状态(Infected)-移除状态(Removed)传播模型(SIR)为研究对象,对双层网络信息传播动力学进行数学建模,信息在层间和层内同时传播。进一步推导双层网络上SIR传播模型传播阈值理论值,讨论影响信息传播的相关因素,并证明双层网络传播阈值不大于单层网络传播阈值,揭示层间连边促进了信息传播原理,最后计算机仿真验证了理论的正确性。

Study on the electric double layer of a cylindrical reverse micelle with functional theoretical approach

The iterative method in functional analysis is applied to looking for a solution of the Poisson-Boltzmann equation in order to describe the problems of the distribution of the potentials in the electric double layer (EDL) inside the water pool for a cylindrical inverse micelle. Potentials as a function of the position of a particular point in EDL are computed, which display a quantitative agreement with those from earlier calculation of Debye and Hückel in the case of low potentials. But it is also shown that in the higher-potential range the iterative calculations can give more accurate re- sults. These results indicate the utility of this functional analysis technique in the description of the properties of EDL for a cylindrical inverse micelle.

Fabrication of Zn-Ti layered double hydroxide by varying cationic ratio of Ti^(4+) and its application as UV absorbent

ZnTi-layered double hydroxides（LDHs） with varying Zn/Ti ratio have been synthesized by coprecipitation of zinc and titanium salts from homogeneous solution.The obtained ZnTi-LDHs possess high crystallinity and hierarchical structure with improved UV-absorbance property.The UV-vis spectra show that the UV absorbing properties of ZnTi-LDHs is stronger and broader than both MgAl-LDH and ZnAl-LDH due to the existence of Ti.Moreover,the UV absorption property increased with the content of Ti,which can be ascribed to the decrease in the band gap energy,as clearly confirmed by density functional theory calculations.When irradiated by UV rays,the property of the samples with generated free radicals（OH^·and O2^·） was evaluated by means of electron spin resonance（EPR）.ZnTi-LDHs generated a relatively lower active radicals in contrast with TiO2 and ZnO,which implied an increased safety used as sunscreens.Therefore,this work provides a detailed understanding of UV shielding properties of ZnTiLDHs which was unrevealed previously,and demonstrates the expansive application prospects of ZnTiLDHs in the field of sunscreens.

Nonlocal Galerkin Strip Transfer Function Method for Vibration of Double-Layered Graphene Mass Sensor

Double-layered graphene sheets （DLGSs） can be applied to the development of a new generation of nanomechanical sensors due to their unique physical properties. A rectangular DLGS with a nanoparticle randomly located in the upper sheet is modeled as two nonlocal Kirchhoff plates connected by van der Waals forces. The Galerkin strip transfer function method which is a semi-analytical method is developed to compute the natural frequencies of the mass- plate vibrating system. It can give exact closed-form solutions along the longitudinal direction of the strip. The results obtained from the semi-analytical method are compared with the previous ones, and the differences between the single-layered graphene sheet （SLGS） and the DLGS mass sensors are also investigated. The results demonstrate the similarity of the in-phase mode between the SLGS and DLGS mass sensors. The sensitivity of the DLGS mass sensor can be increased by decreasing the nonlocal parameter, moving the attached nanoparticle closer to the DLGS center and making the DLGS smaller. These conclusions are helpful for the design and application of graphene-sheet-based resonators as nano-mass sensors.