Fe稳固的FeOOH@NiOOH电催化剂的大电流极化设计与析氧研究

电解水技术是制取高纯度氢气的有效途径,为传统的氢气生产提供了一种可持续的替代方案.其中,开发性能优异的电催化材料是降低电解水制氢成本的关键.析氧反应(OER)由于涉及多个电子转移而导致的动力学缓慢,是克服高过电位的主要挑战.镍铁羟基/氢氧化物(NiFe(oxy)hydroxides)是近期研究的热点,其在碱性条件下具有极低的OER过电位,部分材料性能甚至超过了贵金属基催化剂,如IrO_(2)和RuO_(2).然而,NiFe(oxy)hydroxides的长期催化稳定性,尤其是在大电流下的长期催化稳定性,成为限制其实际应用的主要问题,这主要是由于铁元素的严重流失导致的.因此,如何有效控制和利用电化学溶解/沉积动力学成为稳定铁位点的关键.为克服该挑战,本文提出了一种大电流极化重构方法来固定活性铁位点.通过在大电流(1.5 A cm^(-2))下对材料进行表面快速极化重构,成功制备了FeOOH@NiOOH(eFNO_(L))电催化剂.eFNO_(L)不仅具有稳定的铁位点,还暴露出高指数晶面,因此eFNO_(L)同时展现出较好的OER催化活性和稳定性.同时,密度泛函理论计算结果表明,与具有低指数晶面的FeNiOOH相比,大电流极化工程制备的分相eFNO_(L)对铁位点表现出更高的结合能,可以有效抑制OER过程中的铁流失,且高指数晶面在改变速率决定步骤和减少吸附能垒上具有更大的优势.电化学测试结果表明,经过优化后的eFNO_(L)催化剂在产生100和500 mA cm^(-2)大电流密度仅需234和27 mV的过电位,并且具有较小的Tafel斜率(35.2 mV dec^(-1)).由于铁位点结合能的提高,eFNO_(L)催化剂在500 mA cm^(-2)的电流密度下能够稳定催化超过100 h,且仅有1.5%的性能衰减,优于近期报道的大多数镍铁基OER催化剂.综上,本文为开发高活性和高稳定性能的催化剂提供了一种有效的大电流电化学重构策略,在电解水制氢领域实现其工业化的大规模应用方面显示出巨大潜力,有望降低可持续电解水制氢成本.

Surface Coating Enabling Sulfide Solid Electrolytes with Excellent Air Stability and Lithium Compatibility

All-solid-state lithium metal batteries(ASSLMBs)featuring sulfide solid electrolytes(SEs)are recognized as the most promising next-generation energy storage technology because of their exceptional safety and much-improved energy density.However,lithium dendrite growth in sulfide SEs and their poor air stability have posed significant obstacles to the advancement of sulfide-based ASSLMBs.Here,a thin layer(approximately 5 nm)of g-C_(3)N_(4)is coated on the surface of a sulfide SE(Li_(6)PS_(5)Cl),which not only lowers the electronic conductivity of Li_(6)PS_(5)Cl but also achieves remarkable interface stability by facilitating the in situ formation of ion-conductive Li3N at the Li/Li_(6)PS_(5)Cl interface.Additionally,the g-C_(3)N_(4)coating on the surface can substantially reduce the formation of H_(2)S when Li_(6)PS_(5)Cl is exposed to humid air.As a result,Li-Li symmetrical cells using g-C_(3)N_(4)-coated Li_(6)PS_(5)Cl stably cycle for 1000 h with a current density of 0.2 mA cm^(-2).ASSLMBs paired with LiNbO_(3)-coated LiNi_(0.6)Mn_(0.2)Co_(0.2)O_(2)exhibit a capacity of 132.8 mAh g^(-1)at 0.1 C and a high-capacity retention of 99.1%after 200 cycles.Furthermore,g-C_(3)N_(4)-coated Li_(6)PS_(5)Cl effectively mitigates the self-discharge behavior observed in ASSLMBs.This surface-coating approach for sulfide solid electrolytes opens the door to the practical implementation of sulfide-based ASSLMBs.

Recent progress on mechanisms,principles,and strategies for high-activity and high-stability non-PGM fuel cell catalyst design

The commercialization of a polymer membrane H2-O2 fuel cell and its widespread use call for the development of cost-effective oxygen reduction reaction(ORR)nonplatinum group metal(NPGM)catalysts.Nevertheless,to meet the requests for the real-world fuel cell application and replacing platinum catalysts,it still needs to address some challenges for NPGM catalysts regarding the sluggish ORR kinetics in the cathode and their poor durability in acidic environment.In response to these issues,numerous efforts have been made to study NPGM catalysts both theoretically and experimentally,developed these into the atomically dispersed coordinated metal-nitrogen-carbon(M-N-C)form over the past decades.In this review,we present a comprehensive summary of recent advancements on NPGM catalysts with high activity and durability.Catalyst design strategies in terms of optimizing active-site density and enhancing catalyst stability against demetalization and carbon corrosion are highlighted.It is also emphasized the importance of understanding the mechanisms and principles behind those strategies through a combination of theoretical modeling and experimental work.Especially,further understanding the mechanisms related to the active-site structure and the formation process of the single-atom active site under pyrolysis conditions is critical for active-site engineering.Optimizing the active-site distance is the basic principle for improving catalyst activity through increasing the catalyst active-site density.Theoretical studies for the catalyst deactivation mechanism and modeling stable active-site structures provide both mechanisms and principles to improve the NPGM catalyst durability.Finally,currently remained challenges and perspectives in the future on designing high-performance atomically dispersed NPGM catalysts toward fuel cell application are discussed.

High-Performance Quasi-Solid-State Pouch Cells Enabled by in situ Solidification of a Novel Polymer Electrolyte

Conventional lithium-ion batteries(LIBs)with liquid electrolytes are challenged by their big safety concerns,particularly used in electric vehicles.All-solid-state batteries using solid-state electrolytes have been proposed to significantly improve safety yet are impeded by poor interfacial solid–solid contact and fast interface degradation.As a compromising strategy,in situ solidification has been proposed in recent years to fabricate quasi-solid-state batteries,which have great advantages in constructing intimate interfaces and cost-effective mass manufacturing.In this work,quasi-solid-state pouch cells with high loading electrodes(≥3 m Ah cm^(-2))were fabricated via in situ solidification of poly(ethylene glycol)diacrylate-based polymer electrolytes(PEGDA-PEs).Both single-layer and multilayer quasi-solid-state pouch cells(2.0 Ah)have demonstrated stable electrochemical performance over500 cycles.The superb electrochemical stability is closely related to the formation of robust and compatible interphase,which successfully inhibits interfacial side reactions and prevents interfacial structural degradation.This work demonstrates that in situ solidification is a facile and cost-effective approach to fabricate quasi-solid-state pouch cells with both excellent electrochemical performance and safety.

Facet-dependent Thermal and Electrochemical Degradation of Lithium-rich Layered Oxides

Lithium-rich layered oxides(LLOs)are promising candidate cathode materials for safe and inexpensive high-energy-density Li-ion batteries.However,oxygen dimers are formed from the cathode material through oxygen redox activity,which can result in morphological changes and structural transitions that cause performance deterioration and safety concerns.Herein,a flake-like LLO is prepared and aberration-corrected scanning transmission electron microscopy(STEM),in situ high-temperature X-ray diffraction(HT-XRD),and soft X-ray absorption spectrum(sXAS)are used to explore its crystal facet degradation behavior in terms of both thermal and electrochemical processes.Void-induced degradation behavior of LLO in different facet reveals significant anisotropy at high voltage.Particle degradation originates from side facets,such as the(010)facet,while the close(003)facet is stable.These results are further understood through ab initio molecular dynamics calculations,which show that oxygen atoms are lost from the{010}facets.Therefore,the facet degradation process is that oxygen molecular formed in the interlayer and accumulated in the ab plane during heating,which result in crevice-voids in the ab plane facets.The study reveals important aspects of the mechanism responsible for oxygen-anionic activity-based degradation of LLO cathode materials used in lithium-ion batteries.In particular,this study provides insight that enables precise and efficient measures to be taken to improve the thermal and electrochemical stability of an LLO.

Interfacial Challenges and Strategies toward Practical Sulfide-Based Solid-State Lithium Batteries

All-solid-state lithium batteries are considered as the priority candidates for next-generation energy storage devices due to their better safety and higher energy density.As the key part of solid-state batteries,solid-state electrolytes have made certain research progress in recent years.Among the various types of solid-state electrolytes,sulfide electrolytes have received extensive attention because of their high roomtemperature ionic conductivity and good moldability.However,sulfide-based solid-state batteries are still in the research stage.This situation is mainly due to the fact that the application of sulfide electrolytes still faces challenges in particular of interfacial issues,mainly including chemical and electrochemical instability,unstable interfacial reaction,and solid-solid physical contact between electrolyte and electrode.Here,this review provides a comprehensive summary of the existing interfacial issues in the fabrication of sulfide-based solid-state batteries.The in-depth mechanism of the interfacial issues and the current research progress of the main coping strategies are discussed in detail.Finally,we also present an outlook on the future development of sulfide-based solid-state batteries to guide the rational design of nextgeneration high-energy solid-state batteries.

Current Status and Future Directions in Environmental Stability of Sulfide Solid-State Electrolytes for All-Solid-State Batteries

Recently,sulfide-based solid-state electrolytes(SSEs)have attracted much attention owing to their high ionic conductivity and feasible mechanical features.The environmental stability of sulfide-based SSEs is one of the critical aspects due to the possible decomposition,and ionic conductivity change will affect the fabrication and electrochemical performance of the batteries.Thus,important efforts have been made to reveal and improve their environmental stability,and a timely summary of the progress is urgently needed.In this review,we first clarify the definition of environmental stability and its significance in the context of practical use.After indicating the degradation mechanisms of sulfide-based SSEs,we summarize several effective strategies to improve their stability and also highlight the related theoretical studies.The stability of organic solvents of sulfide SSEs is also summarized and discussed,which may help reliable sulfide SSEs in the battery system.The main target of this review is to gain insights and provide useful guidance to further improve the environmental stability of sulfide SSEs,which will finally promote the commercialization of sulfide-based all-solid-state batteries.

Ab initio Molecular Dynamics Study of Local Atomic Structure Evolution of U–Zr Alloy Melts upon Solidification

We study the local atomic structure evolution of UZr and UZr_(2) alloy melts upon solidification through ab initio molecular dynamics simulations.This is achieved by analyzing in detail the temperature dependence of structure factors,pair correlation functions,the bond angle distributions,Honeycutt-Anderson index and Voronoi tessellation analysis as well as local bond orientation order parameters.We observe that as the temperature decreases the pair correlation functions and structure factors become more structured with clear distinctions at the liquid–solid phase transition temperature.The Honeycutt-Anderson indices and Voronoi tessellation analysis indicate that the liquid phase is predominantly comprised of the icosahedra-like local structures,whose fraction increases with decreasing temperature up to the transition temperature and then abruptly drops at the transition temperature,whereas the bcc-like local atomic structures dominate during the solidification process.Furthermore,the bond orientation order analyses with\({\overline{w}}_{6}\)–\({\overline{q}}_{6}\)correlation map and bond angle distribution imply that the local structures mainly consist of the bcc-type during the solidification below the transition temperature.All the analyses are consistent with each other,showing a first-order liquid to solid phase transition for both UZr and UZr_(2) solid solutions,which only differ in different predicted transition temperatures.This work provides a comprehensive insight into the detailed local structure evolution during the solidification of the U–Zr alloy melts at the atomic level.Similar strategies used here can be extended to studying the liquid–solid phase transition in other alloy systems.

Segregation of Re at theγ/γ'boundary of Ni-based single crystal superalloys revealed by first-principles calculations based Monte-Carlo simulations

Nickel-based single crystal superalloys have been widely used in aero-engines and gas turbine engines.To improve the creep resistance,rhenium is often added to the alloys.However,it is not yet fully under-stood how the added Re elements distribute in the alloys and how the microstructure evolves with the addition of Re.Here,we performed extensive first-principles calculations based Monte-Carlo simulated annealing of Ni-Al-Re ternary alloys with different Re concentrations ranging from 0.5 at.%to 6.0 at.%.The results demonstrate that with the decreasing temperature,most of Re atoms stay in theγphase,while a few of Re atoms stay in theγ'phase and tend to occupy the Al positions.At low temperatures,the Re atoms segregate at theγ/γ'boundary,in good agreement with experiment.We find that the disorder-order transition temperature of the Ni-Al-Re ternary alloys increases with the Re concentration due to the Re-enhanced Al-Al ordering tendency.In addition,we observe that at low temperatures the Re segregation at theγ/γ'boundary promotes the formation of Ni 4 Re-or Ni 8 Re-like local structures as the Re concentration is over 2 at.%.The formation of a large amount of these local structures consumes the Re atoms in solid solutions,and thus from the solid-solution strengthening point of view,this would have a negative influence on the creep resistance of the superalloys.This work provides important atomistic insights on the Re distribution and its effects on the stability of superalloys.

高浓度锂盐电解液

基于1 mol·dm^(-3) LiPF_6/EC的传统非水型电解液已在锂离子电池中应用了20年。高功率、高比能锂离子电池以及锂金属电池(如Li-O_2和Li-S)的发展,对电解液提出了更高的要求,使得电解液的研究与开发到了一个革新换代的阶段。研究者们已经在离子液体、聚合物电解质和无机固态电解质等新型体系研究方面取得一定的研究成果,但是这些新体系存在的本征问题使其商业化应用面临一定的困难。研究者们也开始重新审视已优化的常规液态电解液体系,高浓度锂盐电解液(>3 mol·dm^(-3))再次引起广泛关注。本文综述了高浓度锂盐电解液的发展历程、溶液结构特征、分类标准及其特殊的物理化学性能、锂离子传输性质和电解液/电极相容性;对高浓度锂盐电解液存在的主要问题进行了简要分析,提出了相应的改进措施,展望了高浓度锂盐电解液未来的发展方向,为新型电解液的开发提供了一条新思路。

早产儿视网膜病变激光光凝术后角膜地形图状况

目的:观察早产儿视网膜病变(ROP)激光光凝术后儿童角膜地形图的改变。方法:病例对照研究。收集2015年9月至2018年4月于深圳市眼科医院行激光光凝术后的ROP儿童25例(50眼)为ROP组,同时收集年龄匹配的足月儿童23例(46眼)为对照组。2组儿童均行最佳矫正视力(BCVA)检查,统计分析时转换为LogMAR视力。Sirius眼前节分析系统测量2组儿童的各种角膜参数:角膜前后表面不同直径角膜曲率的最大值(K1)和最小值(K2)、平均角膜曲率(Avg);角膜前后表面不同直径的陡峭半径(rs)、平坦半径(rf)、非球面参数(e)。数据采用独立样本t检验进行分析。结果:ROP组儿童BCVA(LogMAR)(0.24±0.25)较对照组儿童(0.07±0.10)差,2组间差异有统计学意义(t=3.20,P=0.003)。ROP组儿童角膜前后表面不同直径范围的角膜屈光力均比对照组儿童大,差异有统计学意义[K1(角膜前表面3、5、7 mm,角膜后表面3、5、7 mm):t=3.139、3.050、2.710,-4.216、-3.821、-2.474;K2:t=2.816、2.688、2.286,-4.252、-3.883、-3.178;Avg:t=3.190、3.041、2.649,-4.848、-4.271、-3.121。均P<0.05]。ROP组儿童角膜前后表面不同直径范围的角膜形态与对照组儿童比较差异均有统计学意义[rf(角膜前表面6、8 mm,角膜后表面6、8 mm):t=3.395、3.354,-4.427、-4.613;rs:t=2.928、2.807,-4.055、-4.175;e:t=3.437、3.991,2.268、4.355,均P<0.05]。结论:Sirius眼前节分析系统是研究ROP激光光凝术后全角膜发育方面的有利工具。ROP激光光凝术后早产儿儿童与足月产儿童相比,角膜前后表面不同范围的屈光力更大,BCVA更差,在视觉发育过程中更易发生屈光不正等视功能改变。

Nucleation kinetics of paramagnetic and diamagnetic metal melts under a high magnetic field

The influence of a high magnetic field(HMF)on the nucleation kinetics of paramagnetic aluminum and diamagnetic zinc melts has been investigated by differential thermal analysis(DTA).It is found that the application of an HMF increases the undercooling of pure aluminum and pure zinc at the same heatingcooling rates.Moreover,the quantitative analysis of activation energy calculated from the DTA results using the Kissinger method manifests that the HMF reduces the activation energy of pure aluminum and pure zinc.Regardless of magnetism,the nucleation frequency under an HMF is higher than that without an HMF.Furthermore,the increase in undercooling under the HMF is mainly attributed to the increase of the contact angle,calculated by the functional relationship between the cooling rate and undercooling.This result is consistent with the increase of the calculated nucleation work for pure aluminum and pure zinc.Additionally,the increase in undercooling caused by the HMF is partly ascribed to the magnetic field-induced suppression of thermal convection in the undercooled melt.

Controlling and adjusting the concentration distribution during solidification process using static magnetic fields

As concentration distribution changes have important effects on material structures and properties,controlling the concentration distribution is essential to alloy performance.The aim of the present work is to control and adjust the concentration distribution by the static magnetic field.It is found that the magnetic field disperses grain boundary segregation and causes the uniform distribution of concentration.Further,by the three-dimensional computed tomography(3 D-CT) reconstruction,the flow distribution is seen and the effect mechanism of the magnetic field is revealed.The present work may clarify the ambiguous understanding on the effect of the static magnetic field on solidification process.