Pseudocapacitive Lithium Storage of Cauliflower-Like CoFe2O4 for Low-Temperature Battery Operation

Binary transition-metal oxides (BTMOs) with hierarchical micro–nano-structures have attracted great interest as potential anode materials for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical cauliflower-like CoFe₂O₄ (cl-CoFe₂O₄) via a facile room-temperature co-precipitation method followed by post-synthetic annealing. The obtained cauliflower structure is constructed by the assembly of microrods, which themselves are composed of small nanoparticles. Such hierarchical micro–nano-structure can promote fast ion transport and stable electrode–electrolyte interfaces. As a result, the cl-CoFe₂O₄ can deliver a high specific capacity (1019.9 mAh g⁻¹ at 0.1 A g⁻¹), excellent rate capability (626.0 mAh g⁻¹ at 5 A g⁻¹), and good cyclability (675.4 mAh g⁻¹ at 4 A g⁻¹ for over 400 cycles) as an anode material for LIBs. Even at low temperatures of 0 °C and −25 °C, the cl-CoFe₂O₄ anode can deliver high capacities of 907.5 and 664.5 mAh g⁻¹ at 100 mA g⁻¹, respectively, indicating its wide operating temperature. More importantly, the full-cell assembled with a commercial LiFePO₄ cathode exhibits a high rate performance (214.2 mAh g⁻¹ at 5000 mA g⁻¹) and an impressive cycling performance (612.7 mAh g⁻¹ over 140 cycles at 300 mA g⁻¹) in the voltage range of 0.5–3.6 V. Kinetic analysis reveals that the electrochemical performance of cl-CoFe₂O₄ is dominated by pseudocapacitive behavior, leading to fast Li⁺ insertion/extraction and good cycling life.     

Accurate Control of Initial Coulombic Efficiency for Lithium-rich Manganese-based Layered Oxides by Surface Multicomponent Integration

Low initial Coulombic efficiency (ICE) is an obstacle for practical application of Li-rich Mn-based layered oxides (LLOs), which is closely related with the irreversible oxygen evolution owing to the overoxidized reaction of surface labile oxygen. Here we report a NH₄F-assisted surface multicomponent integration technology to accurately control the ICE, by which oxygen vacancies, spinel-layered coherent structure, and F-doping are skillfully integrated on the surface of treated LLOs microspheres. Though the regulation on the removed amount of labile oxygen by surface integrated structure, the ICE of LLOs cathodes can adjust from starting value to 100 %. X-ray absorption spectroscopy, refined X-ray diffraction, and scanning transmission electron microscopy show that the removed labile oxygen mainly comes from Li₂MnO₃-like structure. Even operating at a high cut-off voltage of 5 V, the capacity retention of integrated sample at 200 mA g⁻¹ is still larger than 98 % after 100 cycles.     

HNO to NO Conversion Mechanism with Copper Zinc Superoxide Dismutase,Comparison with Heme Protein Mediated Conversions,and the Origin of Questionable Reversibility

The interconversion of NO and HNO, via copper zinc superoxide dismutase (CuZnSOD), is important in biomedicine and for HNO detection. Many mechanistic questions, including the decades-long debate on reversibility, were resolved in this work. Calculations of various active-site and full-protein models show that the basic mechanism is proton-coupled electron transfer with a computed barrier of 10.98 kcal mol⁻¹, which is in excellent agreement with experimental results (10.62 kcal mol⁻¹), and this nonheme protein-mediated reaction has many significant mechanistic differences compared with the conversions mediated by heme proteins due to geometric and electronic factors. The reasons for the irreversible nature of this conversion and models with the first thermodynamically favorable and kinetically feasible mechanism for the experimental reverse reaction were discovered. Such results are the first for nonheme enzyme mediated HNO to NO conversions, which shall facilitate other related studies and HNO probe development.     

Dendritic-Like Molecules Built on a Pillar[5]arene Core as Hole Transporting Materials for Perovskite Solar Cells

Multi-branched molecules have recently demonstrated interesting behaviour as charge-transporting materials within the fields of perovskite solar cells (PSCs). For this reason, extended triarylamine dendrons have been grafted onto a pillar[5]arene core to generate dendrimer-like compounds, which have been used as hole-transporting materials (HTMs) for PSCs. The performances of the solar cells containing these novel compounds have been extensively investigated. Interestingly, a positive dendritic effect has been evidenced as the hole transporting properties are improved when going from the first to the second-generation compound. The stability of the devices based on the best performing pillar[5]arene material has been also evaluated in a high-throughput ageing setup for 500 h at high temperature. When compared to reference devices prepared from spiro-OMeTAD, the behaviour is similar. An analysis of the economic advantages arising from the use of the pillar[5]arene-based material revealed however that our pillar[5]arene-based material is cheaper than the reference.     

Ca-for-Sr substitution in the thermoelectric [(Sr,Ca)2(O,OH)2]q[CoO2] misfit-layered cobalt-oxide system

Calcium-for-strontium substituted samples of the misfit-layered cobalt-oxide system, [(Sr_1−xCa_x)₂(O,OH)₂]_q[CoO₂], were successfully synthesized up to x=0.2 with a sample-encapsulation technique originally developed for the x=0 end phase. While the x=0 sample has a commensurate match between the two layer blocks (i.e. q=0.5), isovalent Ca-for-Sr substitution induces lattice misfit (i.e. q>0.5). At the same time the Seebeck coefficient gets increased, but the increase in resistivity results in suppressing the thermoelectric power factor. The magnetic anomaly in the x=0 sample gets released upon the Ca substitution for the x=0.2 sample to exhibit an almost Curie-Weiss behavior. It is concluded that with increasing x in [(Sr_1−xCa_x)₂(O,OH)₂]_q[CoO₂] the properties smoothly evolve towards those previously reported for the x=1.0 end member, [Ca_1.7O_2.1H_2.4]_0.58[CoO₂].     

Building a Cocrystal by Using Supramolecular Synthons for Pressure-Accelerated Heteromolecular Azide–Alkyne Cycloaddition

Facilitated by the supramolecular synthons of carboxylic acids and amides through cooperative hydrogen-bonding and arene–perfluoroarene interactions, the azide–alkyne cycloaddition reaction between two different molecules in a cocrystal was achieved. This reaction could be accelerated by pressure using a common hydraulic press equipment with excellent regioselectivity to yield 1,4-triazole products. The absence of decarboxylation side reactions in the products in the solid state demonstrated that this strategy can provide a green synthetic route for products not directly accessible by traditional syntheses in solution.     

A pillar[5]arene-based molecular grapple of hexafluorophosphate

A symmetric pillararene-based receptor formed 1:1 complexes instead of 1:2 with different halide anions. The cooperative multivalent hydrogen-bond interactions changed its structure from pillar to conical. By the addition of F, it can work like an excavator grapple selectively grasps a PF₆^- anion.     

MgAlFe复合氧化物吸收SO2后的再生

对吸收ＳＯ２后的ＭｇＡｌＦｅ复合氧化物进行了氢气还原再生的研究，通过对ＭｇＡｌＦｅ复合氧化物ＢＥＴ、ＸＲＤ表征和用氢气对其还原度的测定。发现复合氧化物在再生时有不同的起始还原温度，而且随着Ｆｅ元素的加入起始反应温度随之下降，还原度增加，还原用氢气浓度在１５－１００％范围内基本不影响材料的还原速率和还原度。氧化物经过１０次吸收和再生实验，它的吸收容量除了第一次有下降外，以后基本不变。     

Evaluation of Kinetic Data for Crystallization of Tio2 Prepared by Hydrolysis Method

The formation of TiO₂ prepared by hydrolysis method was presented. Thermodynamics and kinetics of anatase crystallization reaction were investigated. Differential method of kinetic data evaluation in non-isothermal conditions according toKissinger, Ozawa and Kazeev-Yerofeev was applied. Starting, crystallized and thermally treated powders were determined using X-ray powder diffraction analysis. The characteristic parameters (the activation energy, constant rate and formal kinetic order of reaction) of TiO₂ formation were calculated using DSC data. This revised version was published online in August 2006 with corrections to the Cover Date.     

纳米金属氧化物隔热窗膜及性能研究

本文研究了UV固化纳米金属氧化物(ATO)粒径和涂布厚度与薄膜隔热性能的关系,比较了纳米涂层隔热膜与磁控溅射隔热膜的性能和特点。结果表明,光固化树脂单体等组分的官能度、纳米金属氧化物的用量和纳米材料粒径与涂层的隔热性能有密切关系,合理的材料组合制成的隔热膜隔热率可达到50%以上。两类隔热窗膜的对照测试显示,纳米涂层隔热膜具有高透高隔热和隔热性能稳定的特点,纳米涂层隔热膜湿热老化后红外线透过率变化只有5%左右。