Current Status and Perspectives of Dual-Atom Catalysts Towards Sustainable Energy Utilization

The exploration of sustainable energy utilization requires the imple-mentation of advanced electrochemical devices for efficient energy conversion and storage,which are enabled by the usage of cost-effective,high-performance electro-catalysts.Currently,heterogeneous atomically dispersed catalysts are considered as potential candidates for a wide range of applications.Compared to conventional cata-lysts,atomically dispersed metal atoms in carbon-based catalysts have more unsatu-rated coordination sites,quantum size effect,and strong metal-support interactions,resulting in exceptional catalytic activity.Of these,dual-atomic catalysts(DACs)have attracted extensive attention due to the additional synergistic effect between two adja-cent metal atoms.DACs have the advantages of full active site exposure,high selectiv-ity,theoretical 100%atom utilization,and the ability to break the scaling relationship of adsorption free energy on active sites.In this review,we summarize recent research advancement of DACs,which includes(1)the comprehensive understanding of the synergy between atomic pairs;(2)the synthesis of DACs;(3)characterization meth-ods,especially aberration-corrected scanning transmission electron microscopy and synchrotron spectroscopy;and(4)electrochemical energy-related applications.The last part focuses on great potential for the electrochemical catalysis of energy-related small molecules,such as oxygen reduction reaction,CO_(2) reduction reaction,hydrogen evolution reaction,and N_(2) reduction reaction.The future research challenges and opportunities are also raised in prospective section.

Understanding the Li diffusion mechanism and positive effect of current collector volume expansion in anode free batteries

In anode free batteries(AFBs), the current collector acts as anode simultaneously and has large volume expansion which is generally considered as a negative effect decreasing the structural stability of a battery. Moreover, despite many studies on the fast lithium diffusion in the current collector materials of AFB such as copper and aluminum, the involved Li diffusion mechanism in these materials remains poorly understood. Through first-principles calculation and stress-assisted diffusion equations, here we study the Li diffusion mechanism in several current collectors and related alloys and clarify the effect of volume expansion on Li diffusion respectively. It is suggested that due to the lower Li migration barriers in aluminum and tin, they should be more suitable to be used as AFB anodes, compared to copper, silver, and lead. The Li diffusion facilitation in copper with a certain number of vacancies is proposed to explain why the use of copper with a thickness≤100 nm as the protective coating on the anode improves the lifetime of the batteries. We show that the volume expansion has a positive effect on Li diffusion via mechanical–electrochemical coupling. Namely, the volume expansion caused by Li diffusion will further induce stress which in turn affects the diffusion. These findings not only provide in-depth insight into the operating principle of AFBs, but also open a new route toward design of improved anode through utilizing the positive effect of mechanical–electrochemical coupling.

Preparation of Y^(3+)-doped Bi-_(2)MoO_(6) nanosheets for improved visible-light photocatalytic activity: Increased specific surface area, oxygen vacancy formation and efficient carrier separation

Although Bi_(2)Mo O_(6)(BMO) has recently received extensive attention, its visible-light photocatalytic activity remains poor due to its limited photoresponse range and low charge separation efficiency. In this work, a series of visible-light-driven Y^(3+)-doped BMO(Y-BMO) photocatalysts were synthesized via a hydrothermal method. Degradation experiments on Rhodamine B and Congo red organic pollutants revealed that the optimal degradation rates of Y-BMO were 4.3 and 5.3 times those of pure BMO, respectively. The degradation efficiency of Y-BMO did not significantly decrease after four cycle experiments. As a result of Y^(3+)doping, the crystal structure of BMO changed from a thick layer structure to a thin flower-like structure with an increased specific surface area. X-ray photoelectron spectroscopy showed the presence of highintensity peaks for the O 1s orbital at 531.01 and 530.06 eV, confirming the formation of oxygen vacancies in Y-BMO. Photoluminescence(PL) and electrochemical impedance spectroscopy measurements revealed that the PL intensity and interface resistances of composites decreased significantly, indicating reduced electron–hole pair recombination. This work provides an effective way to prepare high-efficiency Bibased photocatalysts by doping rare earth metal ions for improved photocatalytic performance.

Ⅲ–Ⅴ compound materials and lasers on silicon

Silicon-based photonic integration has attracted the interest of semiconductor scientists because it has high luminous efficiency and electron mobility.Breakthroughs have been made in silicon-based integrated lasers over the past few decades.Here we review three main methods of integration ofⅢ–Ⅴ materials on Si,namely direct growth,bonding,and selectivearea hetero-epitaxy.TheⅢ–Ⅴmaterials we introduced mainly include materials such as GaAs and InP.The lasers are mainly lasers of related communication bands.We also introduced the advantages and challenges of the three methods.

Blind Nonlinearity Equalization by Machine-Learning-Based Clustering for QAM-Based Quantum Noise Stream Cipher Transmission

In quantum noise stream cipher(QNSC)systems,it is difficult to compensate fiber nonlinearity by digital signal processing(DSP)due to interactions between chromatic dispersion(CD),amplified spontaneous emission(ASE)noise from erbiumdoped fiber amplifier(EDFA)and Kerr nonlinearity.Nonlinearity equalizer(NLE)based on machine learning(ML)algorithms have been extensively studied.However,most NLE based on supervised ML algorithms have high training overhead and computation complexity.In addition,the performance of these algorithms have a lot of randomness.This paper proposes two clustering algorithms based on Fuzzylogic C-Means Clustering(FLC)to compensate the fiber nonlinearity in quadrature amplitude modulation(QAM)-based QNSC system,including FLC based on subtractive clustering(SC)and annealing evolution(AE)algorithm.The performance of FLC-SC and FLC-AE are evaluated through simulation and experiment.The proposed algorithms can promptly obtain suitable initial centroids and choose optimal initial centroids of the clusters to achieve the global optimal initial centroids especially for high order modulation scheme.In the simulation,different parameter configurations are considered,including fiber length,optical signal-to-noise ratio(OSNR),clipping ratio and resolution of digital to analog converter(DAC).Further-more,we measure the Q-factor of transmission signal with different launched powers,DAC resolution and laser linewidth in the optical back-to-back(BTB)experiment with 80-km single mode fiber.Both simulation and experimental results show that the proposed techniques can greatly mitigate the signal impairments.

全方位立体化实践育人模式的构建与实践

吉林大学化学国家级实验教学示范中心对不同阶段的学生引入科普启迪、兴趣引导、实验训练等教学方式,从低到高,由浅入深,构建和实践了启蒙、引导、培养的全方位立体化实践育人模式,并取得了一定的成效。未来,中心将继续探索和实践化学拔尖人才的培养,以适应新时代下对具有批判创新思维的人才的需求。

“双支撑、三结合”化学安全实践育人体系的构建

随着社会对化学专业人才安全素养的要求日益提高,各高校逐渐意识到化学实验室安全教育的重要性。但当前的化学安全教育普遍缺乏系统性,为了扭转这样的局面,吉林大学化学学院依托化学国家级实验教学示范中心为平台,基于OBE (Outcome-Based Education)教育理念,以硬件建设和知识载体为双支撑、采取“理论与实践相结合、课内课外相结合、虚拟与现实相结合”的三结合实施路径,构建化学安全实践育人体系,使学生安全意识、安全知识和应急能力螺旋式上升,全面提升学生的化学安全素养。

定制电解液或隔膜实现锂离子各向异性输运从而抑制枝晶生长:相场模拟研究

电池内部不可控的枝晶生长问题严重地影响着电池的循环性能和安全性能,这对于锂金属电池的实际应用是一个严峻的挑战。尽管已有较多的实验和理论研究工作聚焦于电极间锂离子各向异性输运特性对枝晶形貌的影响,但仍有一些开放性的问题有待进一步研究,例如,如何将枝晶生长的动态演变与电解液性质、电势分布或隔膜多孔结构诱导的锂离子各向异性输运关联起来。我们通过将锂离子在电解液中的扩散系数(D_(L))表示为二阶张量的形式并进行相场模拟,发现D_(yy):D_(xx)比值的增加,以及电势诱导的电极/电解液界面锂离子快速扩散层均可以降低界面处锂离子浓度梯度和电势梯度,从而减弱枝晶生长的驱动力。我们还发现隔膜基体与y方向之间夹角的增大也会显著促进电解质中的锂离子各向异性输运特性,以利于抑制枝晶生长。籍此本文提出设计D_(yy):D_(xx)=10:1的电解液和基体倾斜角为arctan(0.5)的隔膜用于锂金属电池。该相场研究有望为设计具有抑制枝晶能力的电解质或隔膜提供指导。

Model Building and Anisotropy of PrFeB Permanent Magnetic Materials

This paper considers that the crystal grains of HDDR Pr2Fe14B permanent magnetic material are cubic, the size is 0.3 μm, and the crystal grains are in simple cubic accumulation. It is considered that there are boundary phases between grains. It is assumed that the boundary phases are non-magnetic phases with the thickness of d, and evenly distributed between grains. The anisotropy expression of single grain boundary is given considering structure defect and intergranular exchange coupling interaction. Based on micro-magnetic simulation calculation, the variation of the average anisotropy of a single grain with the structural defects and boundary phases was calculated. The results show that when the thickness of structural defects is constant, the average anisotropy of a single grain decreases with increasing of grain boundary phase thickness, and while the thickness of grain boundary phase is constant, it also decreases with increasing of structural defect thickness.

柞蚕丝素肽的抗氧化及美白功效评价

开展柞蚕丝素肽的抗氧化及美白功效研究。结果显示,1号(分子量2000-5000 Da)和2号(分子量<2000 Da)样品对DPPH自由基清除率的IC50分别是1.41和3.84 mg/mL,对羟基自由基清除率的IC50分别是0.085和0.091 mg/mL,总还原力水平随着样品添加剂量的增加而升高。柞蚕丝素肽的添加对紫外氧化损伤的小鼠成纤维细胞具有保护作用,能够提高超氧化物歧化酶(SOD)活力和谷胱甘肽(GSH)含量,降低丙二醛(MDA)含量。在美白功效评价方面,1号和2号样品对酪氨酸酶抑制率的IC50分别为3.65和5.84 mg/mL,并能够降低小鼠黑素瘤细胞内黑色素合成和酪氨酸酶活性。总之,柞蚕丝素肽具有抗氧化和美白活性,且分子量较大的1号样品优于2号样品。

洞庭湖典型垸内沟渠沉积物不同形态氮的赋存特征

随着人类活动影响的加剧，洞庭湖局部区域已经出现轻中度富营养化，为了探究影响洞庭湖富营养化的因素，采用连续分级提取法针对洞庭湖垸内沟渠开展沉积物不同形态氮的赋存特征研究。结果表明研究区域沉积物总氮（TN）含量在586.82—1438．35mg·kg^-1之间，各形态氮的含量大小依次为：酸解态氮（HN）〉残渣态氮（RN）〉可交换态氮（EN）〉游离态氮（FN），分别占沉积物总氮的69．27％、16．72％、13．32％、0．69％。可矿化程度较高的HN占比最高，总可矿化有机氮平均277．15mg／kg，沉积物向上覆水中释放氮的能力较高，存在加剧洞庭湖区水体富营养化程度的风险，本研究可为洞庭湖沟渠水体富营养化控制和治理提供一定的理论依据。

Atomically Dispersed Fe-N_4 Modified with Precisely Located S for Highly Efficient Oxygen Reduction

Immobilizing metal atoms by multiple nitrogen atoms has triggered exceptional catalytic activity toward many critical electrochemical reactions due to their merits of highly unsaturated coordination and strong metal-substrate interaction.Herein,atomically dispersed Fe-NC material with precise sulfur modification to Fe periphery(termed as Fe-NSC) was synthesized,X-ray absorption near edge structure analysis confirmed the central Fe atom being stabilized in a specific configuration of Fe(N3)(N-C-S).By enabling precisely localized S doping,the electronic structure of Fe-N4 moiety could be mediated,leading to the beneficial adjustment of absorption/desorption properties of reactant/intermediate on Fe center.Density functional theory simulation suggested that more negative charge density would be localized over Fe-N4 moiety after S doping,allowing weakened binding capability to *OH intermediates and faster charge transfer from Fe center to O species.Electrochemical measurements revealed that the Fe-NSC sample exhibited significantly enhanced oxygen reduction reaction performance compared to the S-free Fe-NC material(termed as Fe-NC),showing an excellent onset potential of 1.09 V and half-wave potential of 0.92 V in 0.1 M KOH.Our work may enlighten relevant studies regarding to accessing improvement on the catalytic performance of atomically dispersed M-NC materials by managing precisely tuned local environments of M-Nx moiety.

Application of phase-field method in rechargeable batteries

Rechargeable batteries have a profound impact on our daily life so that it is urgent to capture the physical and chemical fundamentals affecting the operation and lifetime.The phase-field method is a powerful computational approach to describe and predict the evolution of mesoscale microstructures,which can help to understand the dynamic behavior of the material systems.In this review,we briefly introduce the theoretical framework of the phase-field model and its application in electrochemical systems,summarize the existing phase-field simulations in rechargeable batteries,and provide improvement,development,and problems to be considered of the future phase-field simulation in rechargeable batteries.

Understanding the separator pore size inhibition effect on lithium dendrite via phase-field simulations

Dendrite growth in lithium-ion batteries may bring thermal run-away especially at high current densities,which remains the major bottleneck to implement safe and fast charging for portable electronic devices or electronical vehicles.Designing dendrite inhibition separators with proper pore size is considered to be one of the most promising strategies to guarantee the battery safety.However,due to the impossible observation of lithium-ion distribution under separator by experiments,the underlying dendrite inhibition mechanism is still not fully understood.Here,we apply the phase-field model,which takes the separator phase into account to construct the electrochemical system total free energy,to study the ion re-distribution behavior of porous separator and understand the pore size inhibition effect on lithium dendrite.The numerical results indicate that separator with smaller pore size is beneficial to smoother electrodeposition,since the lithium-ion concentration on the electrode surface is more uniform under denser separator pores,when their sizes is larger than the critical nucleus.The proposed model could capture the physicochemical process of electrodeposition under multiphase structures,so it could also be used to explore dendrite growth under composite electrodes and composite solid electrolytes.

Phase-field simulation tending to depict practical electrodeposition process in lithium-based batteries

Lithium dendrite growth due to uneven electrodeposition usually leads to the potential hazard of internal short circuit and shorter lifetime of lithium-based batteries. Extensive efforts have been devoted to explore the effects of single or two factors on dendrite growth, involving the diffusion coefficient, exchange current density, electrolyte concentration, temperature, and applied voltage. However, these factors interrelate during battery operation, signifying that a understanding of how they jointly influence the electrodeposition is of paramount importance for the effective suppression of dendrites. Here, we incorporate the dependent relationships among key factors into the phase-field model to capture their synergistic effects on electrodeposition. All the simulations are implemented in our self-written MATLAB code under a unified modeling framework. Following this, five groups of experimentally common dendrite patterns are reproduced and the corresponding electrodeposition driving forces are identified. Unexpectedly, we find that with the decrease of the ratio of exchange current density(or applied voltage) to diffusion coefficient, the electrodeposition morphology changes from needle-like dendrites to columnar dendrites and to uniform deposition. The present phase-field simulation tends to depict the practical electrodeposition process, providing important insights into synergistic regulation to suppress dendrite growth.

Unified Picture on Temperature Dependence of Lithium Dendrite Growth via Phase-Field Simulation

Lithium dendrite growth due to uneven electrodeposition may penetrate the separator and solid electrolyte,causing inner short circuit and potential thermal runaway.Despite great electrochemical phase-field simulation efforts devoted to exploring the dendrite growth mechanism under the temperature field,no unified picture has emerged.For example,it remains open how to understand the promotion,inhibition,and dual effects of increased temperature on dendrite growth when using different electrolyte types.Here,by comprehensively considering the temperature-dependent Li_(+)diffusion coefficient,electrochemical reaction coefficient,and initial temperature distribution in phase-field model,we propose that the activation-energy ratio,defined as the ratio of electrochemical reaction activation energy to electrolyte Li+diffusion activation energy,can be used to quantify the effect of temperature on dendrite morphology.Specifically,we establish a mechanism diagram correlating the activation-energy ratio,uniform initial temperature,and maximum dendrite height,which unifies the seemingly contradictory simulation results.Furthermore,results based on nonuniform initial temperature distribution indicate that a positive temperature gradient along the discharging current facilitates uniform Li+deposition and local hotspot should be avoided.These findings provide valuable insights into the temperature-dependent Li dendrite growth and contribute to the practical application of Li metal batteries.

Mg-Li Hybrid Batteries:The Combination of Fast Kinetics and Reduced Overpotential

It is imperative for the development of cost-effective and high-performance batteries.Currently,lithium-ion batteries still occupy most of the market.However,limited lithium(Li)resource and energy density retard their further development.The magnesium(Mg)metal has several significant advantages;those make it a viable alternative to Li as anode,including high volume specific capacity and dendrite-free plating during cycling and high abundance.The Mg-Li hybrid batteries can combine the advantages of Li ion and Mg metal to achieve fast electrode kinetics and smooth anode deposition morphology.This review summarizes recent progresses in cathode material design and anode interface modification for Mg-Li hybrid batteries.We aim to illustrate the contribution of Li^(+)to the electrochemical performance improvement at both cathode and anode sides and to provide inspiration for the future research in this field.

Pattern reconfigurable antenna array for 5.8 GHz WBAN applications

A pattern reconfigurable antenna array for 5.8 GHz wireless body area network(WBAN)applications is proposed in this paper.The antenna array consists of a radiation component and a controller component.The radiation component comprises four planar F-shaped antennas,which are located on the four corners of the upper layer and are rotated 90°anticlockwise from each other.

Software for Evaluating Ionic Conductivity of Inorganic-Polymer Composite Solid Electrolytes

Inorganic-polymer composite solid electrolytes(IPCSEs)obtained by filling the polymer matrix with inorganic materials usually have higher ionic conductivity compared with individual phases.This important increase in ionic conductivity is explained in terms of the new percolation paths formed by the highly conductive interface between inorganic filler and polymer.The conduction in such systems can be investigated using the effective medium theory(EMT)and random resistance model(RRM).EMT can be used to analyze the effect of filler size on the ionic conductivity of disordered IPCSEs,while RRM can describe the composites with inorganic fillers of various shapes(nano-particles,nano-wires,nano-sheets,and nano-networks)in ordered or disordered arrangement.Herein,we present software evaluating the ionic conductivity in IPCSEs by combining EMT and RRM.The approach is illustrated by considering the size,shapes,and arrangements of inorganic fillers.The ionic conductivities of different types of IPCSEs are predicted theoretically and found in good agreement with the experimental values.The software can be used as an auxiliary tool to design composite electrolytes.

Boost photothermal theranostics via self-assembly-induced crystallization(SAIC)

Owing to the intrinsic advantages of spatiotemporal selectivity,photothermal theranostics have become the advancing edge of precision medicine for cancer.Developing photothermal transduction agents(PTAs)with near-infrared(NIR)absorption,high photothermal conversion efficiency,robust photothermal stability,and good accumulation in tumors,is particularly valuable.Herein,we report a new concept,self-assembly-induced crystallization(SAIC),which can serve as a mechanism that dramatically boosts photothermal behaviors of PTA in NIR region.As a proof of concept,three heptamethine cyanine molecules with internal degrees of freedom(geometry and intramolecular interaction)are designed to fine-tune their crystallinity.Notably,Cy7-TCF-EMBI molecules with rigid and planar skeletons self-assemble into a crystalline state to maximize their packing density and improve the charge transfer,both of which contribute to nonradiative decay for energy dissipation as heat.The high packing density also renders an ideal scaffold for controlling intermolecular interactions to exhibit better photothermal stability,and endows an anisotropic three-dimensional architecture for passive tumor targeting.This“SAIC”strategy may offer a conceptually novel,practically simple but effective approach to unveil the structure–property relationship that could provide some general rules in rational design of PTAs,and paves the way for a next generation of supramolecular medicine for photothermal theranostics.