通过TEMPO增强脱氢和OH吸附促进中性电解质中5-羟甲基糠醛的电催化氧化

生物质衍生物的电催化转化为可持续能源的增值利用提供了一条绿色高效的途径.例如,由5-羟甲基糠醛(HMF)氧化可得到生物基聚酯前驱体2,5-呋喃二甲酸(FDCA),对于缓解化石资源带来的能源危机和环境问题具有重要意义.目前,HMF的电催化氧化通常在强碱性(pH>13.5)溶液中进行,但是容易产生难以分离的腐殖质,影响FDCA的工业利用.另外,强碱性介质还存在腐蚀安全隐患、设备维护成本高等问题.中性反应条件有助于改善上述问题,但是缺乏亲电氧物种(例如OH-),HMF和催化剂的活化困难,难以得到高附加值产物FDCA.目前,针对中性介质中HMF的电催化氧化研究少有报道,急需明晰中性介质中HMF的催化机理,并开发中性条件下具有高活性的催化剂体系.本文利用均相催化剂2,2,6,6-四甲基哌啶-1-氧基(TEMPO)和Co_(3)O_(4)电极,对HMF进行中性条件下电催化氧化,1.55 VRHE条件下反应1.5 h,以接近100%转化率获得产物FDCA,产率大于99%.而在无TEMPO的条件下,HMF在Co_(3)O_(4)电极上转化率小于2%.原位红外等实验测试及理论计算结果表明,低电位(1.10 VRHE)下形成的TEMPO+阳离子的活化能显著减低HMF,通过脱氢作用选择性生成中间产物2,5-二甲酰基呋喃(DFF),对调控HMF的氧化路径、促进中性介质电催化氧化起到关键作用.原位X射线光电子能谱和电化学阻抗等结果发现,TEMPO存在时,1.35 V后,在含有高价态Co^(3+)/^(4+)的Co_(3)O_(4)电极上出现更多的水以及OH吸附物种,并导致HMF的氧化电流密度以及FDCA的转化率显著增加.理论计算结果表明,TEMPO自由基与水分子存在较强的氢键作用,有利于促进水活化提供OH.然而,低电位(1.25 V)以Co_(3)O_(4)为电极,或高电位(1.55 V)以泡沫镍为电极,即使添加TEMPO,电极上没有出现相应的OH吸附行为和电化学活性提升现象.因此,活性的Co_(3)O_(4)电极对于协同水的解离形成OH具有重要作用,二者共同作用下,水活化解离形成Co^(3+)/^(4+)-(OH)_(ads)活性中心.在中性溶液中,亲电氧物种OHads提供氧源,促进DFF等甲酰基中间体进一步氧化转化为FDCA.综上,本文加深了对中性介质中HMF的电催化氧化机制的理解,对设计类似电催化剂体系有借鉴作用.

Advances in the structure design of substrate materials for zinc anode of aqueous zinc ion batteries

Aqueous zinc ion batteries(AZIBs) demonstrate tremendous competitiveness and application prospects because of their abundant resources,low cost, high safety, and environmental friendliness. Although the advanced electrochemical energy storage systems based on zinc ion batteries have been greatly developed, many severe problems associated with Zn anode impede its practical application, such as the dendrite formation,hydrogen evolution, corrosion and passivation phenomenon. To address these drawbacks, electrolytes, separators, zinc alloys, interfacial modification and structural design of Zn anode have been employed at present by scientists. Among them, the structural design for zinc anode is relatively mature, which is generally believed to enhance the electroactive surface area of zinc anode, reduce local current density, and promote the uniform distribution of zinc ions on the surface of anode. In order to explore new research directions, it is crucial to systematically summarize the structural design of anode materials. Herein, this review focuses on the challenges in Zn anode, modification strategies and the three-dimensional(3D) structure design of substrate materials for Zn anode including carbon substrate materials, metal substrate materials and other substrate materials. Finally, future directions and perspectives about the Zn anode are presented for developing high-performance AZIBs.

水系锌二次电池MnO_(2)正极的晶体结构、反应机理及其改性策略

水系锌二次电池凭借其安全性高、环境友好、成本低廉、能量密度较高等诸多优势,有望应用于下一代大规模储能系统。电池的发展依赖于电极材料,二氧化锰由于其高丰度、低成本、毒性小等优势,在水系锌二次电池领域得到广泛应用。本文将从二氧化锰的晶体结构、反应机理及电化学性能出发,对其在水系锌二次电池中的研究进展进行系统综述。特别地,针对其容量低、循环稳定性差等问题,本文从储能机理(包括嵌入-脱嵌机制和溶解-沉积机制)角度出发,总结相对应的优化策略,为先进水系锌锰二次电池的设计开发提供参考。

B-doped and La_(4)NiLiO_(8)-coated Ni-rich cathode with enhanced structural and interfacial stability for lithium-ion batteries

Ni-rich layered oxides are considered promising cathodes for advanced lithium-ion batteries(LIBs)in the future,owing to their high capacity and low cost.However,the issues on structural and interfacial stability of Ni-rich cathodes still pose substantial obstacles in the practical application of advanced LIBs.Here,we employ a one-step method to synthesize a B-doped and La_(4)NiLiO_(8)-coated LiNi_(0.82)5Co_(0.115)Mn_(0.06)O_(2)(BL-1)cathode with reliable structure and interface,for the first time.The La_(4)NiLiO_(8)coating layer can prevent cathodes from electrolyte assault and facilitate Li+diffusion kinetics.Moreover,B-doping can effectively restrain the pernicious H_(2)-H_(3) phase transition and adjust the orientation of primary particles to a radial alignment,which is obstructive to the arise of microcracks induced by the change of anisotropic volume.Specifically,when tested in pouch cells,the BL-1 cathode exhibits outstanding capacity retention of 93.49%after 500 cycles at 1 C.This dual-modification strategy dramatically enhances the stability of the structure and interface for Ni-rich cathode materials,consequently accelerating the commercialization process of high-energy–density LIBs.

Highly Dispersed Cobalt Nanoparticles Embedded in Nitrogen-Doped Graphitized Carbon for Fast and Durable Potassium Storage

Potassium-ion batteries(KIBs)have great potential for applications in large-scale energy storage devices.However,the larger radius of K+leads to sluggish kinetics and inferior cycling performance,severely restricting its practical applicability.Herein,we propose a rational strategy involving a Prussian blue analogue-derived graphitized carbon anode with fast and durable potassium storage capability,which is constructed by encapsulating cobalt nanoparticles in nitrogen-doped graphitized carbon(Co-NC).Both experimental and theoretical results show that N-doping effectively promotes the uniform dispersion of cobalt nanoparticles in the carbon matrix through Co-N bonds.Moreover,the cobalt nanoparticles and strong Co-N bonds synergistically form a threedimensional conductive network,increase the number of adsorption sites,and reduce the diffusion energy barrier,thereby facilitating the adsorption and the diffusion kinetics.These multiple effects lead to enhanced reversible capacities of 305 and 208.6 mAh g^−1 after 100 and 300 cycles at 0.05 and 0.1 A g^−1,respectively,demonstrating the applicability of the Co-NC anode for KIBs.

Functional carbon materials for high-performance Zn metal anodes

The realization of“carbon peak”and“carbon neutralization”highly depends on the efficient utilization of renewable energy sources.Exploring reliable and low-cost electrochemical energy storage systems is an ever-growing demand for renewable energy integration.Among available candidates,aqueous zinc-ion batteries(AZIBs)receive extensive researchers'attention because of their material abundance,high capacity,high safety,and environmental friendliness.However,the irreversible issues of Zn anode in terms of notorious dendric Zn growth,Zn corrosion/hydrogen evolution,and passivation significantly impede the commercialization of high-performance AZIBs.Carbon materials have advantages of large specific surface area,low cost,high electrical conductivity,controllable structure,and good stability.Their application provides remedies for improving the comprehensive performance of Zn anodes.In this review,the fundamentals and issues of Zn anodes,and the research progress with functional carbon materials for Zn anodes in recent years are presented.Three major strategies are described in detail,including the use of carbon materials(carbon nanotubes,graphene,carbon fiber,metal-organic framework(MOF)derived host,etc.)as Zn plating/stripping substrates,as protective coating layers on Zn,and as electrolyte additives.Finally,the remaining challenges and perspectives of carbon materials in high-performance AZIBs are outlined.

Infant Cry Language Analysis and Recognition:An Experimental Approach

Recently, lots of research has been directed towards natural language processing. However, the baby's cry, which serves as the primary means of communication for infants, has not yet been extensively explored, because it is not a language that can be easily understood. Since cry signals carry information about a babies' wellbeing and can be understood by experienced parents and experts to an extent, recognition and analysis of an infant's cry is not only possible, but also has profound medical and societal applications. In this paper, we obtain and analyze audio features of infant cry signals in time and frequency domains.Based on the related features, we can classify given cry signals to specific cry meanings for cry language recognition. Features extracted from audio feature space include linear predictive coding(LPC), linear predictive cepstral coefficients(LPCC),Bark frequency cepstral coefficients(BFCC), and Mel frequency cepstral coefficients(MFCC). Compressed sensing technique was used for classification and practical data were used to design and verify the proposed approaches. Experiments show that the proposed infant cry recognition approaches offer accurate and promising results.

Understanding the growth mechanisms of metal-based core–shell nanostructures revealed by in situ liquid cell transmission electron microscopy

Metal-based core-shell nanostructures have garnered enduring interest due to their unique properties and functionalities.However,their growth and transformation mechanisms in liquid media remain largely unknown because they lack direct observation of the dynamic growth process with high spatial and temporal resolution.Developing the in situ liquid cell transmission electron microscopy(TEM)technique offers unprecedented real-time imaging and spectroscopy capabilities to directly track the evolution of structural and chemical transformation of metal-based core–shell nanostructures in liquid media under their working condition.Here,this review highlights recent progress in utilizing in situ liquid cell TEM characterization technique in investigating the dynamic evolution of material structure and morphology of metal-based core–shell nanostructures at the nano/atomic scale in real-time.A brief introduction of the development of liquid cells for in situ TEM is first given.Subsequently,recent advances in in situ liquid cell TEM for the fundamental study of growth mechanisms of metal based core–shell nanostructures are discussed.Finally,the challenge and future developments of metalbased core–shell nanostructures for in situ liquid cell TEM are proposed.Our review is anticipated to inspire ongoing interest in revealing unseen growth dynamics of core–shell nanostructures by in situ liquid cell TEM technique.

Synergistic chemical and electrochemical strategy for high-performance Zn//MnO_(2) batteries

Aqueous rechargeable Zn//MnO_(2)batteries have been considered as the promising candidate for future energy storage system due to their economic and environmental merits.However,the high-performance Zn//MnO_(2)batteries are plagued by poor sluggish reaction kinetics and capacity degradation due to the strong electrostatic interactions and complicated reaction process.Herein,the synergistic effect of atom defects engineering and phase transformation mechanism is confirmed as the effective strategy to enhance ion/charge transfer kinetics and structural stability.Defects gradient controlling and electrochemically induced phase transformation from spinel to layered structure render the aqueous Zn//λ-MnO_(2)system delivers a high discharge capacity of 285 m Ah/g and capacity retention of 81%after 500 cycles.

Hydrated ammonium manganese phosphates by electrochemically induced manganese-defect as cathode material for aqueous zinc ion batteries

Aqueous zinc ion batteries(AZIBs) with the merits of low cost, low toxicity, high safety, environmental benignity as well as multi-valence properties as the large-scale energy storage devices demonstrate tremendous application prospect. However, the explorations for the most competitive manganese-based cathode materials of AZIBs have been mainly limited to some known manganese oxides. Herein, we report a new type of cathode material NH_(4)MnPO_(4)·H_(2)O(abbreviated as AMPH) for rechargeable AZIBs synthesized through a simple hydrothermal method. An in-situ electrochemical strategy inducing Mn-defect has been used to unlock the electrochemical activity of AMPH through the initial charge process, which can convert poor electrochemical characteristic of AMPH towards Zn^(2+)and NH_(4)+into great electrochemically active cathode for AZIBs. It still delivers a reversible discharge capacity up to 90.0 m Ah/g at 0.5 A/g even after 1000thcycles, which indicates a considerable capacity and an impressive cycle stability. Furthermore, this cathode reveals an(de)insertion mechanism of Zn^(2+)and NH_(4)+without structural collapse during the charge/discharge process. The work not only supplements a new member for the family of manganese-based compound for AZIBs, but also provides a potential direction for developing novel cathode material for AZIBs by introducing defect chemistry.

Tea-derived carbon materials as anode for high-performance sodium ion batteries

Sodium-ion batteries(SIB) have attracted widespread attention in large-scale energy storage fields owing to the abundant reserve in the earth and similar properties of sodium to lithium. Biomass-based carbon materials with low-cost, controllable structure, simple processing technology, and environmental friendliness tick almost all the right boxes as one of the promising anode materials for SIB. Herein, we present a simple novel strategy involving tea tomenta biomass-derived carbon anode with enhanced interlayer carbon distance(0.44 nm) and high performance, which is constructed by N,P co-doped hard carbon(Tea-1100-NP) derived from tea tomenta. The prepared Tea-1100-NP composite could deliver a high reversible capacity(326.1 m Ah/g at 28 m A/g), high initial coulombic efficiency(ICE = 90% at 28 m A/g),stable cycle life(262.4 m Ah/g at 280 m A/g for 100 cycles), and superior rate performance(224.5 m Ah/g at 1400 m A/g). Experimental results show that the excellent electrochemical performance of Tea-1100-NP due to the high number of active N,P-containing groups, and disordered amorphous structures provide ample active sites and increase the conductivity, meanwhile, large amounts of microporous shorten the Na+diffusion distance as well as quicken ion transport. This work provides a new type of N,P co-doped high-performance tomenta-derived carbon, which may also greatly promote the commercial application of SIB.

中性或弱酸性体系下锌基水系电池负极材料研究进展

锌具有原料丰富、质量轻便、金属导电性与延展性好以及理论比容量高等优势,可以作为绿色可充电电池的理想电极材料。其中,以中性或弱酸性水溶液为电解质、锌为负极的锌基水系电池具有安全性高、电池材料廉价无毒、制备工艺简单、环境友好等特点,在储能和动力电池领域具有极高的应用价值和发展前景。但电池充放电过程中伴随的锌枝晶、析氢、腐蚀、钝化等问题限制了其实际应用。本文综述了锌基水系电池负极存在的问题及当前的解决策略,并对其负极研究发展方向进行了展望。

水系锌离子电池锰基正极材料

水系锌离子电池(AZIBs)以低成本、高安全性和高环保特性在大规模储能领域具有广阔的应用前景,当前备受关注的正极材料是研究的热点。锰基化合物因具有资源丰富、环境友好和价格低廉等优点,是最具市场应用前景的一类正极材料。本文详细综述了不同锰基化合物的结构特点以及锰基AZIBs在充放电过程中涉及的四种储能机理,讨论了AZIBs锰基正极材料目前存在的问题和优化策略。最后,提出了AZIBs锰基正极材料具有研究前景的可能性方向,以期对AZIBs的发展起到一定的预见作用。

Pt嵌入Ni3Se2@NiOOH核壳结构作为双功能催化剂提高全解水性能（英文）

制备具有高效氢析出和氧析出双功能的电催化剂对提高大规模电解水制氢效率至关重要.迄今为止,无论是贵金属还是过渡金属化合物都未能达到令人满意的效果.本文采用原位化学反应法制备了三维枝状Pt-Ni3Se2@NiOOH/NF(PNOF)纳米阵列.泡沫镍作为镍源可有效减少界面电阻的影响,表面NiOOH含有大量氧空位,这些有效措施使PNOF催化剂同时具有优异的氢析出和氧析出性能.同时作为电解水制氢的阴极和阳极, PNOF催化剂全解水电位在1.52 V即可实现10 mA cm^-2的电流密度,并具有良好的稳定性.这项工作为开发新型全解水催化剂提供了一种有效的方法.

Alkali-metal(Li, Na, and K)-adsorbed MoSi_(2)N_(4) monolayer: an investigation of its outstanding electronic, optical, and photocatalytic properties

Single-layer MoSi_(2)N_(4),a high-quality two-dimensional material,has recently been fabricated by chemical vapor deposition.Motivated by this latest experimental work,herein,we apply first principles calculations to investigate the electronic,optical,and photocatalytic properties of alkali-metal(Li,Na,and K)-adsorbed MoSi_(2)N_(4) monolayer.The electronic structure analysis shows that pristine MoSi_(2)N_(4) monolayer exhibits an indirect bandgap(E_(g)=1.89 eV).By contrast,the bandgaps of one Li-,Na-,and K-adsorbed MoSi_(2)N_(4) monolayer are 1.73 eV,1.61 eV,and 1.75 eV,respectively.Moreover,the work function of MoSi_(2)N_(4) monolayer(4.80 eV)is significantly reduced after the adsorption of alkali metal atoms.The work functions of one Li-,Na-,and K-adsorbed MoSi_(2)N_(4) monolayer are 1.50 eV,1.43 eV,and 2.03 eV,respectively.Then,optical investigations indicate that alkali metal adsorption processes substantially increase the visible light absorption range and coefficient of MoSi_(2)N_(4) monolayer.Furthermore,based on redox potential variations after alkali metals are adsorbed,Li-and Na-adsorbed MoSi_(2)N_(4) monolayers are more suitable for the water splitting photocatalytic process,and the Li-adsorbed case shows the highest potential application for CO_(2) reduction.In conclusion,alkali-metal-adsorbed MoSi_(2)N_(4) monolayer exhibits promising applications as novel optoelectronic devices and photocatalytic materials due to its unique physical and chemical properties.