Improved electrochemical performance of nano-crystalline Li2FeSiO4/C cathode material prepared by the optimization of sintering temperature

Li₂FeSiO₄/C cathode materials have been prepared using the conventional solid-state method by varying the sintering temperature (650 °C, 700 °C and 750 °C), and the structure and electrochemical performance of Li₂FeSiO₄/C materials are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), galvanostatic charge–discharge tests, respectively. The results show that Li₂FeSiO₄ nano-crystals with a diameter of about 6–8 nm are inbedded in the amorphous carbon, and the Li₂FeSiO₄/C material obtained at 700 °C exhibits an initial discharge capacity of 195 mA?h g^?1 at 1/16 C in the potential range of 1.5–4.8 V. The excellent electrochemical performance of Li₂FeSiO₄/C attributes to the improvement of conductivity and reduction of impurity by the optimization of the sintering temperature.     

NN型双齿半夹心Ru(Ⅱ)化合物:无受体脱氢环化合成喹啉和吡咯衍生物的催化剂

四个含NN型双齿配体的半夹心(η^6-p-cymene)Ru(II)化合物被成功制备.这四个化合物分别为(η^6-p-cymene)-Ru(C5H4N-C5H3N-OH)(1),(η^6-p-cymene)Ru(C5H4N-CH2-C5H4N)(2),(η^6-p-cymene)Ru(C5H4N-CH2-C5H3N-OH)(3)和(η^6-p-cymene)Ru(C5H4N-CH2-C5H3N-OCH3)(4).这些化合物通过核磁氢谱、碳谱和元素分析等手段表征,化合物2的结构被X射线单晶衍射证实.将这些化合物应用于催化氨醇与酮的环化反应,其中3的催化效率最高.在0.5mol%化合物3的存在下,制备了一系列喹啉和吡啶衍生物.     

Mild Synthesis of Pt/SnO2/Graphene Nanocomposites with Remarkably Enhanced Ethanol Electro‐oxidation Activity and Durability

We have designed a new Pt/SnO₂/graphene nanomaterial by using L ‐arginine as a linker; this material shows the unique Pt‐around‐SnO₂ structure. The Sn²⁺ cations reduce graphene oxide (GO), leading to the in situ formation of SnO₂/graphene hybrids. L ‐Arginine is used as a linker and protector to induce the in situ growth of Pt nanoparticles (NPs) connected with SnO₂ NPs and impede the agglomeration of Pt NPs. The obtained Pt/SnO₂/graphene composites exhibit superior electrocatalytic activity and stability for the ethanol oxidation reaction as compared with the commercial Pt/C catalyst owing to the close‐connected structure between the Pt NPs and SnO₂ NPs. This work should have a great impact on the rational design of future metal–metal oxide nanostructures with high catalytic activity and stability for fuel cell systems.     

Synthesis of the chain-shaped carbon fibers decorated with SiO<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> beads by chemical vapor deposition

Chain-shaped carbon fibers decorated with SiO _x beads had been synthesized by using methyltriehlorosilane and normal carbon fibers as the raw materials, during which the chemical vapor deposition technique was applied. The products were characterized by scanning electron microscopy (SEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD) and Raman spectroscopy. The as-received products show chain-shaped morphologies that have the normal carbon fibers as “strings” and possess regular SiO _x beads of 30–40 μm with relative smooth surface. The formation of the chain-shaped morphology is considered to involve the shrinkage of the absorbed silica layer and the possible growth mechanism is further proposed. It is thought that the chain-shaped carbon fibers are formed by two main stages.     

关于Fuzzy度量点式刻画的一点注记

本文中重新定义由一个点式Ｆｕｚｚｙｐ．ｑ．度量ｄ所诱导的Ｆｕｚｚｙｐ．ｑ．度量｛Ｄｒ｜ｒ＞０｝（代替［１］中的相关重域映射族）．在新的定义下，点式Ｆｕｚｚｙｐ．ｑ．（ｐ．）度量与Ｆｕｚｚｙｐ．ｐ．（ｐ．）度量之间有令人满意的──对应关系．     

化学电源制造工程研究生校内实践课程创新性教学探索

如何培养专业硕士的实践和创新能力是高等教育工作者不断探索的问题。本文以哈尔滨工业大学化学电源制造工程实践课程为例,针对该课程存在的问题,从教学手段、教学内容、教师队伍和评价体系四个方面进行课程改革。构建了研究生课内外全方位自主学习的教学体系,对有效利用实践课程提升学生的工程实践、创新及科研能力进行有益的探索。     

A multifunctional silicotungstic acid-modified Li-rich manganese-based cathode material with excellent electrochemical properties

Journal of Solid State Electrochemistry - Li-rich layered oxide (LrLO) cathode has attracted much attention for Li-ion batteries in recent years due to its superior capacity of exceeding...     

Influence of accidental overcharging on the performance and degradation mechanisms of LiCoO<Subscript>2</Subscript>/mesocarbon microbead battery

The accidental overcharging is emulated in fully charged LiCoO₂/mesocarbon microbeads (MCMB) batteries through initial one-off overcharging and successive long-term normal cycling. The aging mechanism and effect of accidental overcharging on the performance of LiCoO₂/MCMB battery is studied by the electrochemical tests and physical characterizations. The result clearly shows that not all accidentally overcharged batteries should be discarded and the extent of the degradation is highly dependent on the overcharging cutoff voltages. Compared with the blank batteries, low overcharging cutoff voltages have almost no influence on the performance degradation during successive long-term normal cycling. Under this condition, the aging is primarily due to the consumption of active lithium. However, high overcharging cutoff voltages, even just one time, decay the battery. Furthermore, further cycling accelerates the aging and changes the aging mechanism of battery under normal operation condition. Under this condition, the surface structure destruction of the LiCoO₂ is revealed as the primary contributor to battery degradation, which is related to the dissolution and reduction of cobalt ions after overcharging at high cutoff voltages and successive long-term normal cycling.     

碳纳米管电极上原位沉积Pt纳米颗粒

 本文利用原位离子交换法制备了碳纳米管(CNTs)载铂(Pt/CNTs)电极. X射线光电子能谱分析表明, Pt通过离子交换载于电化学功能化的CNTs表面. 扫描电镜照片显示, Pt高度分散于CNTs表面. X射线衍射分析表明, Pt的粒径约为4.0 nm. 离子交换法所制Pt/CNTs电极的电化学表面积和Pt的利用率均大于传统Pt/CNTs电极(Pt粒径约为2.5 nm), 其对氧还原的催化活性高于传统电极. 这归因于离子交换法所制电极的特殊结构,即Pt普遍载于电化学活性位上.