Two-dimensional hybrid nanomaterials derived from MXenes(Ti_3C_2T_x)as advanced energy storage and conversion applications

The development of two-dimensional hybrid nanomaterial derived from MXenes as high performance electrode material is the key component for the advanced ene rgy storage and conversion systems.In the past decades,MXene derived nanomaterials have attracted greatly interest in scientific activity and potential applications because of their unique synergistic properties such as high thermal stability,excellent electrical conductivity,large surface area,easy to handle and outstanding electro and photo chemical properties.This review is focused on the synthesis of hybrid nanomaterials from MXene(Ti_3C_2T_x) for renewable energy conversion and storage application including hydrogen evolution reaction,supercapacitor,lithium-ion batteries and photocatalysis.Finally,we also summarized the prospect and opportunities of novel two-dimensional hybrid nanomaterials derived MXene(Ti_3C_2T_x) fo r futuristic sustainable energy technology.     

Synthesis, structure and photocatalytic activity of nano TiO2 and nano Ti1-xMxO2-δ (M = Cu, Fe, Pt, Pd, V, W, Ce, Zr)

We have synthesized 5–7 nm size, highly crystalline TiO₂ which absorbs radiation in the visible region of solar spectrum. The material shows higher photocatalytic activity both in UV and visible region of the solar radiation compared to commercial Degussa P25 TiO₂. Transition metal ion substitution for Ti⁴⁺ creates mid-gap states which act as recombination centers for electron-hole induced by photons thus reducing photocatalytic activity. However, Pt, Pd and Cu ion substituted TiO₂ are excellent CO oxidation and NO reduction catalysts at temperatures less than 100° C.     

Improved anti-Stokes energy transfer between rare earth ions in Er（0.5）Yb（9.5）：FOV oxyfluoride vitroceramics explains the strong color reversal

The widely used energy transfer theory is a foundation of luminescence,in which the rates of Stokes and antiStokes processes have the same calculation formula.An improvement on the anti-Stokes energy transfer to explain the fluorescence intensity reversal between the red and green fluorescence of Er(0.5)Yb(9.5):FOV is reported in the present article.The range of the intensity reversal Σ was measured to be 877.Dynamic processes for 16 levels were simulated.A coefficient,the improvement factor of the intensity ratio of Stokes to anti-Stokes processes in quantum Raman theory compared to classical Raman theory,is introduced to successfully describe the anti-Stokes energy transfer.A new method to calculate the distance between the rare earth ions,which is critical for the energy transfer calculation,is proposed.The validity of these important improvements is also proved by experiment.     

有机纳米分子聚集体PIC-I的Raman光谱研究

本文从分子聚集体ＰＩＣ－Ｉ的吸收光谱可观测到Ｊ－带的红移和窄化,并可算出１３６８ｃｍ－１振模,以及本实验条件下聚集体单体数目为Ｎ≈３链长为３×０．３ｎｍ＝０．９ｎｍ。测量了ＰＩＣ－Ｉ聚集体的荧光光谱,将它与吸收光谱相比较可以看出,聚集体吸收带（５７２．５ｎｍ）和荧光发射带（５７２．５ｎｍ）是共振的。系统地研究了ＰＩＣ－Ｉ聚集体的喇曼光谱（１００～１８００ｃｍ－１）,验证了振动模 １３６８ｃｍ－１的存在。     

Effects of Preparation Parameters on the Characteristics of NiPxBY Nanomaterials

A series of NiP _x B _y nanomaterials were prepared by a chemical reduction method under various preparation parameters. Experiment results show that the different preparation parameters affected the morphology, particle size, surface area and the composition of the sample. However, they did not influence the electronic state of nickel. The type of solution showed significant influence on the properties of the sample, whereas, the type of nickel salt did not. The particle size of NiPB, NiB, and NiP were 10–30 nm. The NiP sample prepared in the aqueous solution had the largest particle size 50–150 nm. If the solvent was 50% ethanol in water, the surface area of the sample significantly increased nine fold for NiP and four fold for NiPB powders. In contrast, the surface area of NiB did not increase. The NiPB, NiB, and NiP powders had a spherical morphology if they were prepared with aqueous solution. The NiPB prepared in 50% ethanol solution showed floss morphology and had a very high surface area.     

DNA分子组装体研究进展*

DNA分子组装体在基因治疗、电子转移、分子器件和纳米材料构筑等方面具有很强的应用前景.本文对近几年来DNA分子组装体的研究作了评述.     

Bio‐inspired iron/sulfur/graphene nanocomposite and its use in the catalysis of the oxygen reduction reaction at room temperature in alkaline media on a glassy carbon electrode

This work demonstrates the performance of a bio‐inspired iron/sulfur/graphene nanocomposite as a non‐platinum electrocatalyst for the oxygen reduction reaction (ORR) in an alkaline medium. The catalyst shows the most positive ORR onset potential (1.1 V vs. RHE) according to its unique structure in the alkaline medium (KOH solution, pH = 13) at low temperature (T = 298 K). The catalyst is evaluated by the rotating‐disk electrode (RDE) method under various rotating speeds (0–2,000 rpm) in the potential range ?0.02–1.18 V vs. a rechargeable hydrogen electrode (RHE). The number of transferred electrons, as one of the most important parameters, is almost constant over a wide range of potentials (0.1–0.8 V), which indicates a more efficient four‐electron pathway from O₂ to H₂O on the FePc‐S‐Gr surface. The mean size of catalyst centers are in the nanoscale (<10 nm). The estimated Tafel slope in the appropriate range is about ?110 mV per decade at low current density, and E_1/2 of FePc‐S‐Gr displays a negative shift of only 7.1 mV after 10,000 cycles.     

Two dimensional nanomaterial‐based separation membranes

Two dimensional nanomaterials including graphene, hexagonal boron‐nitride, molybdenum disulfide, etc., provide immense potentials for separation applications. However, the tradeoff between selectivity and permeability in choosing 2D nanomaterial‐based membrane is inevitable, limiting the progress on separation efficiency for mass industrial applications. To target these issues, versatile strategies such as the rational design of predefined interlayer channels, membrane nanopores, and reasonable functionalization, as well as new mechanisms have been emerged. In this review, we introduce the recent progress on separation mechanisms of 2D nanomaterial‐based membranes with different structures (including the interlayer channels type and the membrane nanopores type) and their inner surface functionalization. Moreover, the interface designs are discussed, in terms of employing dynamic liquid–liquid/liquid–gas interfaces, to advance the selectivity and permeability of the membranes. We further discuss the variety of separation applications based on 2D nanomaterial‐based membranes. The authors hope this review will inspire the active interest of many scientists in the area of the development and application of membrane science.     

Improving the charge transfer performance of Si nanomaterial through C surface modification: A first-principles study

Models of oxidized Si (111) surface under different C coverage were established to study the charge transfer ability of Si nanomaterial from strategy of C surface modification using first-principles calculation. The calculated formation energies show that structures of C surface-modified oxidized Si (111) surface are stable. The electronic properties present that the interaction between C and Si atoms is mainly contributed by the hybridization of C-2p and Si-3p states. And the interaction between C and Si atoms increases firstly and then decreases with the increasing C coverage rate. The transfer charge between C and Si reaches a maximum when C coverage rate is 0.5. We speculate that the conductivity of experimentally prepared Si nanomaterial does not monotonously enhance with the increasing C concentration, which would reach a maximum at a certain C concentration, and then decreases.     

复杂一维纳米材料的构筑及储钠性能

一维纳米材料因其独特的结构和物化性质而被广泛应用于能源存储与转换等领域. 钠离子电池由于钠资源储量丰富和成本低廉等特点而有望用于大规模能源存储. 随着能源需求的不断增长和研究的日益深入,一维纳米材料也经历着结构从简单到复杂、性能从一般到优异的演变. 因此,构筑结构复杂独特、储钠性能优异的一维纳米材料已成为储能领域的热点之一. 结合当前的研究热点和本课题组的研究进展,本文重点阐述了有机酸辅助干燥法、水热法和静电纺丝法制备复杂一维纳米材料的详细机理及其储钠性能,材料包括束状纳米线、介孔纳米管、豌豆状纳米管和离子预嵌入纳米带等,并对它们的结构与储钠性能相关性进行了详细分析. 这为一维纳米材料后续的研究和应用提供了一定的指导和帮助.