微纳米纤维素功能膜在能源与环境领域的应用

探寻绿色清洁的资源与材料以维持高效的社会经济增长是未来数十年人们面临的最大挑战之一. 可持续资源与绿色材料的开发是降低传统化石能源与材料比重的最有前途的方案. 纤维素作为一种可持续发展、 可生物再生、 储量丰富且低成本的天然高分子聚合物, 在众多领域中具有广泛的应用, 并且纤维素可以加工成各种构型, 包括气凝胶、 泡沫、 海绵和薄膜等. 本文介绍了不同形态的纤维素及其衍生物组装而成的功能膜在能源与环境中的应用, 综述了微纳米纤维素及其衍生物在先进功能化储能器件方面的最新进展和制备方案, 以及在用于水处理的膜分离技术中的应用, 其中重点讨论了微纳米纤维素及其衍生物功能膜在电池、 电容器及水处理等领域中的作用, 如隔膜、 柔性电极膜和分离膜等. 此外, 还对纤维素及其衍生物功能膜的未来发展进行了总结和展望.     

Vacancy‐Rich Ni(OH)2 Drives the Electrooxidation of Amino C−N Bonds to Nitrile C≡N Bonds

Electrochemical synthesis based on electrons as reagents provides a broad prospect for commodity chemical manufacturing. A direct one‐step route for the electrooxidation of amino C?N bonds to nitrile C≡N bonds offers an alternative pathway for nitrile production. However, this route has not been fully explored with respect to either the chemical bond reforming process or the performance optimization. Proposed here is a model of vacancy‐rich Ni(OH)₂ atomic layers for studying the performance relationship with respect to structure. Theoretical calculations show the vacancy‐induced local electropositive sites chemisorb the N atom with a lone pair of electrons and then attack the corresponding N(sp³)?H, thus accelerating amino C?N bond activation for dehydrogenation directly into the C≡N bond. Vacancy‐rich nanosheets exhibit up to 96.5 % propionitrile selectivity at a moderate potential of 1.38 V. These findings can lead to a new pathway for facilitating catalytic reactions in the chemicals industry.     

Giant Tunability of Charge Transport in 2D Inorganic Molecular Crystals by Pressure Engineering

The unique intermolecular van der Waals force in emerging two-dimensional inorganic molecular crystals (2DIMCs) endows them with highly tunable structures and properties upon applying external stimuli. Using high pressure to modulate the intermolecular bonding, here we reveal the highly tunable charge transport behavior in 2DIMCs for the first time, from an insulator to a semiconductor. As pressure increases, 2D α-Sb₂O₃ molecular crystal undergoes three isostructural transitions, and the intermolecular bonding enhances gradually, which results in a considerably decreased band gap by 25 % and a greatly enhanced charge transport. Impressively, the in situ resistivity measurement of the α-Sb₂O₃ flake shows a sharp drop by 5 orders of magnitude in 0–3.2 GPa. This work sheds new light on the manipulation of charge transport in 2DIMCs and is of great significance for promoting the fundamental understanding and potential applications of 2DIMCs in advanced modern technologies.     

Enhancing the performances of Li-ion batteries by carbon-coating: present and future

With progress of knowledge of electrode materials, it has been found that their surface structures are of great importance to the electrochemical performance of Li-ion batteries. Carbon coating can effectively increase the electrode conductivity, improve the surface chemistry of the active material, and protect the electrode from direct contact with electrolyte, leading to enhanced cycle life of the batteries. Carbon coating together with nanotechnology provides good conductivity as well as fast Li-ion diffusion, and thus also results in good rate capabilities. The recent development of carbon coating techniques in lithium-ion batteries is discussed with detailed examples of typical cathode and anode materials. The limitation of current technology and future perspective of the new concept of "hybrid coating" are also pointed out.     

Hierarchical micro/nano porous silicon Li-ion battery anodes

A wet-chemical etching method is reported for the scale-up preparation of carbon-coated hierarchical micro/nano porous silicon powders as a Li-ion battery anode, which shows no capacity fading at 1500 mA h g(-1) in 50 charge/discharge cycles.     

Revealing the conversion mechanism of CuO nanowires during lithiation-delithiation by in situ transmission electron microscopy

Being promising candidates for anodes in lithium-ion batteries (LIBs), transition metal oxide anodes utilizing the so-called conversion mechanism principle typically suffer from the severe capacity fading during the 1st cycle of lithiation-delithiation. Herein, we directly investigated these processes using an individual CuO nanowire anode and constructed a lithium ion battery (LIB) prototype within a transmission electron microscope.     

CoO octahedral nanocages for high-performance lithium ion batteries

Pure-phase CoO octahedral nanocages were successfully fabricated by a novel simple method. The coordination etching agents play key roles in the formation of these non-spherical hollow structures. When tested as anode materials in lithium ion batteries (LIBs), these nanocages showed excellent cycling performance, good rate capability and enhanced lithium storage capacity.     

An unsymmetrical lithium-ion pathway between charge and discharge processes in a two-phase stage of Li4Ti5O12

In this work, we investigated lithium-ion diffusion in spinel Li(4)Ti(5)O(12) nano-particles with carbon coating by electrochemical impedance spectroscopy (EIS), and proposed a hybrid model of the unsymmetrical lithium-ion pathway between charge and discharge processes. In this hybrid model, the charge process still follows the core-shell model, but in the discharge process, the phase transition evolves by growth of a few nuclei on the surface. And this hybrid model is possibly attributed to the nonuniform electron conductivity inside the Li(4)Ti(5)O(12) particles. Additionally, the relaxation process and the particle morphology are also carefully discussed in the experiment to show that this hybrid model is quite practical. Thereby, this investigation presents an unsymmetrical lithium-ion pathway in Li(4)Ti(5)O(12) particles, which could be extended to other active materials in lithium ion batteries.     

Large-scale synthesis of single-crystal hexagonal tungsten trioxide nanowires and electrochemical lithium intercalation into the nanocrystals

Single-crystal nanowires of hexagonal tungsten trioxide in a large scale have been successfully prepared by a simple hydrothermal method without any templates and catalysts. Uniform h-WO₃ nanowires with diameter of 25-50 nm and length of up to several micrometers are obtained. It is found that the morphology and crystal form of the final products are strongly dependent on the amount of the sulfate and pH value of the reaction system. The electrochemical performances of the as-prepared h-WO₃ nanowires as anodic materials of Li-ion batteries have also been investigated. It deliveres a discharge capacity of 218 mAh g⁻¹ for the first cycle. In addition, the cycle ability of the nanocrystals is superior to that of bulk materials, which implies the morphology and particle size have the influence on the electrochemical performances.     

A New Overdispersed Integer-Valued Moving Average Model with Dependent Counting Series

A new integer-valued moving average model is introduced. The assumption of independent counting series in the model is relaxed to allow dependence between them, leading to the overdispersion in the model. Statistical properties were established for this new integer-valued moving average model with dependent counting series. The Yule–Walker method was applied to estimate the model parameters. The estimator’s performance was evaluated using simulations, and the overdispersion test of the INMA(1) process was applied to examine the dependence between counting series.