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1.
Previous density-functional theory (DFT) calculations show that sub-nanometric Cu clusters (i.e., 13 atoms) favorably generate CH4 from the CO2 reduction reaction (CO2RR), but experimental evidence is lacking. Herein, a facile impregnation-calcination route towards Cu clusters, having a diameter of about 1.0 nm with about 10 atoms, was developed by double confinement of carbon defects and micropores. These Cu clusters enable high selectivity for the CO2RR with a maximum Faraday efficiency of 81.7 % for CH4. Calculations and experimental results show that the Cu clusters enhance the adsorption of *H and *CO intermediates, thus promoting generation of CH4 rather than H2 and CO. The strong interactions between the Cu clusters and defective carbon optimize the electronic structure of the Cu clusters for selectivity and stability towards generation of CH4. Provided here is the first experimental evidence that sub-nanometric Cu clusters facilitate the production of CH4 from the CO2RR.  相似文献   
2.
Recently, nonmetal doping has exhibited its great potential for boosting the hydrogen evolution reaction (HER) of transition-metal (TM)-based electrocatalysts. To this end, this work overviews the recent achievements made on the design and development of the nonmetal-doped TM-based electrocatalysts and their performance for the HER. It is also shown that by rationally doping nonmetal elements, the electronic structures of TM-based electrocatalysts can be effectively tuned and in turn the Gibbs free energy of the TM for adsorption of H* intermediates (ΔGH*) optimized, consequently enhancing the intrinsic activity of TM-based electrocatalysts. Notably, we highlight that concurrently doping two nonmetal elements can continuously and precisely regulate the electronic structures of the TM, thereby maximizing the activity for HER. Moreover, nonmetal doping also accounts for enhancing the physical properties of the TM (i.e. surface area). Therefore, nonmetal doping is a robust strategy for simultaneous regulation of the chemical and physical features of the TM.  相似文献   
3.
以聚偏氟乙烯(PVDF)和硅藻土为原料,通过静电纺丝法制备PVDF@硅藻土复合纤维膜,用于锂离子电池隔膜。 研究了隔膜的吸液率、热稳定性和电化学性能等。 添加硅藻土可有效提高复合膜的电解液吸收率和电化学性能,其中吸液率可达623.6%,相比于PVDF膜和聚丙烯(PP)膜具有优异的循环性能和倍率性能。  相似文献   
4.
李欣  赵强  郝建红  董志伟  薛碧曦 《强激光与粒子束》2020,32(2):025024-1-025024-6
作为航天器电源系统的重要组成部分,太阳电池需要更高的转换效率和可靠性以及更长的使用寿命。通过在太阳电池表面覆盖抗辐照玻璃盖片,可以增强太阳电池对粒子辐射的防护,延长太阳电池的服役寿命,使航天器获得可靠的能源供应。硼硅酸盐玻璃就是一种理想的太阳电池玻璃盖片材料。采用蒙特卡罗方法,结合SRIM软件模拟研究质子辐照硼硅酸盐玻璃的损伤物理机理。基于粒子与物质相互作用的理论以及基本公式,通过分析不同入射能量的质子在硼硅酸盐玻璃中的阻止本领、电离能损、位移能损、空位的产生情况,对辐照损伤的物理机制进行研究。结果表明:能量为30~120 keV的质子辐照损伤主要发生在硼硅酸盐玻璃表面;质子沉积、空位分布等均为Bragg峰型分布;电离能损是能量损失的主要部分,随入射能量的增加而增大,导致电子的电离和激发;位移能损在玻璃内部随能量降低而增大,导致硼、氧和硅等空位缺陷的产生;电离效应和缺陷的产生是硼硅酸盐玻璃色心形成的重要原因。  相似文献   
5.
采用流动控制沉积法, 通过调控泵速和聚甲基丙烯酸甲酯(PMMA)胶体微球溶液的浓度, 制备出微球排列高度有序且薄膜紧密附着于基底的高质量光子晶体薄膜. 获得了制备高质量PMMA光子晶体薄膜的组装条件范围, 发现在该条件范围内, 当泵速或胶体微球溶液浓度一定时, PMMA光子晶体薄膜的厚度随胶体微球溶液浓度的增加或泵速的降低而增加. 研究了组装条件对PMMA光子晶体薄膜光学性能的影响, 发现光子禁带位置随光子晶体薄膜厚度增加或减少而红移或蓝移. 在此基础上, 控制组装条件得到了不同尺寸微球堆叠而成的叠层光子晶体薄膜, 并研究了其光学性能的变化规律. 结果显示, 叠层光子晶体薄膜的光子禁带峰为各层叠层光子晶体禁带峰的简单叠加, 且峰强度受光入射角方向影响.  相似文献   
6.
In this study, a biochar-based magnetic solid-phase microextraction method, coupled with liquid chromatography–mass spectrometry, was developed for analyzing fentanyl analogs from urine sample. Magnetic biochar was fabricated through a one-step pyrolysis carbonization and magnetization process, followed by an alkali treatment. In order to achieve desired extraction efficiency, feed stocks (wood and bamboo) and different pyrolysis temperatures (300–700°C) were optimized. The magnetic bamboo biochar pyrolyzed at 400°C was found to have the greatest potential for extraction of fentanyls, with enrichment factors ranging from 58.9 to 93.7, presumably due to H-bonding and π–π interactions between biochar and fentanyls. Various extraction parameters, such as type and volume of desorption solvent, pH, and extraction time, were optimized, respectively, to achieve the highest extraction efficiency for the target fentanyls. Under optimized conditions, the developed method was found to have detection limits of 3.0–9.4 ng/L, a linear range of 0.05–10 μg/L, good precisions (1.9–9.4% for intrabatch, 2.9–9.9% for interbatch), and satisfactory recoveries (82.0–111.3%). The developed method by using magnetic bamboo biochar as adsorbent exhibited to be an efficient and promising pretreatment procedure and could potentially be applied for drug analysis in biological samples.  相似文献   
7.
Due to climate change and an increase of favourable habitat, ticks and tick-borne diseases are reported to expand to northern areas in north America. One main factor for lone star ticks to be established in Canada is due to the migration of white-tailed deers from US. In this work, we formulate a compartmental model to study the dynamics of lone star ticks and white-tailed deers, with a focus on migration effect of white-tailed deers. The tickhost interaction and the effect of deer migration are explored analytically and numerically. The positivity of the populations in the model is proved, and the unique positive equilibrium is proved to be asymptotically stable. We conduct sensitivity analysis on a set of parameters, revealing the correlation between the parameters and equilibrium populations. Numerical results show that migration rate of white-tailed deer is one crucial parameter that increases the populations of (infected) ticks and (infected) hosts.  相似文献   
8.
Highly dispersed Ni/SBA-15 catalysts were prepared via template extraction with varying different extraction times (Ni/S-x, x = 0.5, 3.5, 6.5 h) for methane reforming with carbon dioxide. Based on the various characterization results and initial activity evaluation, Ni/S-3.5 h catalyst showed the best catalytic performance. Compared with the catalyst prepared via template calcination (Ni-S), Ni/S-3.5 h catalyst held steady with CH4 and CO2 conversions while those of the Ni-S catalyst respectively decreased by 15 and 11% during the long-term stability test at 700 °C for 50 h. As TEM and TG–DSC results confirmed, Ni particles in spent Ni/S-3.5 h catalyst stayed well-dispersed with size slightly increasing from an initial 3.9–4.1 nm and nearly no carbon deposition was observed. On the contrary, Ni-S catalyst was subjected to sintered metal particles (increased from 11.6 to 18 nm) and formed carbon fibers. The prominent resistance to sintering and coking over stable Ni/S-3.5 h catalyst was attributed to the high dispersion and strengthened metal-support interaction induced via the residual in situ templates.  相似文献   
9.
High‐speed countercurrent chromatography is a liquid–liquid separation chromatographic technique, which has the unique feature of eliminating irreversible adsorption using liquid support medium, and is widely used in research and development of traditional Chinese medicine, biochemistry, food, environment analysis, and so on. In this review, some new developments of countercurrent chromatography, for instance cross‐axis countercurrent chromatography, dual countercurrent chromatography, foam countercurrent chromatography, and pH‐zone‐refining countercurrent chromatography are presented. Furthermore, the research and progress in high‐speed countercurrent chromatography techniques and its application in the separation and purification of terpenoids and saponins are reviewed.  相似文献   
10.
Hydrophobic association hydrogels were fabricated via micellar copolymerization of acrylamide and hydrophobic monomers lauryl (meth)acrylate (LA or LMA) in an aqueous solution of sodium dodecyl sulfate. The effect of methyl groups of hydrophobic monomers on the crosslinking network structure and mechanical behavior of the gels was investigated on the basis of rubber elastic theory. It was found that the LMA-gel exhibited higher effective crosslink density and elastic modulus. The methyl groups of hydrophobic monomers limited the flexibility of the methacrylate backbone in the association domain, which resulted in the increment of chains constraints. With the increase of stretch rate, the dissipated energy of LMA-gel increased more highly than that of LA-gel. In addition, the methyl group hindered the movement of polymer chains, leading to the lower recovery efficiency of dissipated energy for LMA-gel. In contract, the LA-gel exhibited a rapid response to external force, and possessed better elasticity and self-recovery property. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1505–1512  相似文献   
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