Nitrogen doped porous carbon as excellent dual anodes for Li- and Na-ion batteries

Biomass-derived carbon materials have obtained great attention due to their sustainability,easy availability,low cost and environmentally benign.In this work,bamboo leaves derived nitrogen doped hierarchically porous carbon have been efficiently synthesized via an annealing approach,followed by an etching process in HF solution.Electrochemical measurements demonstrate that the unique porous structure,together with the inherent high nitrogen content,endow the as-derived carbon with excellent lithium/sodium storage performance.The porous carbon annealed at 700℃presents outstanding rate capability and remarkable long-term stability as anodes for both lithium-ion batteries and sodium-ion batteries.The optimized carbon delivers a high discharge capacity of 450 mAh/g after 500 cycles at the current density of 0.2 A/g for LIBs,and a discharge capacity of 180 mAh/g after 300 cycles at the current density of 0.1 A/g for SIBs.     

In situ sulfur isotopes (δS and δS) analyses in sulfides and elemental sulfur using high sensitivity cones combined with the addition of nitrogen by laser ablation MC-ICP-MS

The sulfur isotope is an important geochemical tracer in diverse fields of geosciences. In this study, the effects of three different cone combinations with the addition of N₂ on the performance of in situ S isotope analyses were investigated in detail. The signal intensities of S isotopes were improved by a factor of 2.3 and 3.6 using the X skimmer cone combined with the standard sample cone or the Jet sample cone, respectively, compared with the standard arrangement (H skimmer cone combined with the standard sample cone). This signal enhancement is important for the improvement of the precision and accuracy of in situ S isotope analysis at high spatial resolution. Different cone combinations have a significant effect on the mass bias and mass bias stability for S isotopes. Poor precisions of S isotope ratios were obtained using the Jet and X cones combination at their corresponding optimum makeup gas flow when using Ar plasma only. The addition of 4–8 ml min⁻¹ nitrogen to the central gas flow in laser ablation MC-ICP-MS was found to significantly enlarge the mass bias stability zone at their corresponding optimum makeup gas flow in these three different cone combinations. The polyatomic interferences of OO, SH, OOH were also significantly reduced, and the interference free plateaus of sulfur isotopes became broader and flatter in the nitrogen mode (N₂ = 4 ml min⁻¹). However, the signal intensity of S was not increased by the addition of nitrogen in this study. The laser fluence and ablation mode had significant effects on sulfur isotope fractionation during the analysis of sulfides and elemental sulfur by laser ablation MC-ICP-MS. The matrix effect among different sulfides and elemental sulfur was observed, but could be significantly reduced by line scan ablation in preference to single spot ablation under the optimized fluence. It is recommended that the d₉₀ values of the particles in pressed powder pellets for accurate and precise S isotope analysis should be less than 10 μm. Under the selected optimized analytical conditions, excellent agreements between the determined values and the reference values were achieved for the IAEA-S series standard reference materials and a set of six well-characterized, isotopic homogeneous sulfide standards (PPP-1, MoS₂, MASS-1, P-GBW07267, P-GBW07268, P-GBW07270), validating the capability of the developed method for providing high-quality in situ S isotope data in sulfides and elemental sulfur.     

硼烯化合物的合成及应用

In most cases, borylenes containing boron (I) are unstable. In this article, we proceed from the electron configuration of borylene and review the common methods of stabilizing this category of compounds through a series of borylenes in literature. In addition, the article briefly introduces the metallic borylenes and non-metallic borylenes and their properties. Some of these properties have been applied in nitrogen fixation.     

Factors affecting the reactivity and selectivity in the oxidation of sulfides with tetra-n-butylammonium peroxomonosulfate catalyzed by Mn(III) porphyrins: Significant nitrogen donor effects

The oxidation of aryl sulfides by tetra-n-butylammonium peroxomonosulfate (n-Bu₄NHSO₅) was carried out in the presence of six different manganese (III) tetraarylporphyrins [Mn(Por)s] as biomimetic catalysts and a number of nitrogen donors as co-catalysts. There is no noticeable difference between the reactivity of sulfides, in the presence of electron-rich Mn(por)s, whereas, for electron-deficient catalysts, conversion rates are different. Nevertheless, the over-oxidation of sulfoxide is more sensitive to both the nature of substituents attached to the sulfur atom in substrates as well as porphyrin complex structure. The degree of catalytic activity of Mn(Por)s for the formation of sulfone product increases as the following order: Mn(TPFPP)OAc < Mn[T(4-NO₂P)P]OAc < Mn(TDCPP)OAc < Mn(TPP)OAc < Mn(TMP)OAc < Mn[T(4-OMeP)P]OAc. Our results show that in the presence of electron-rich Mn(Por)s, the strong π-donor N-H imidazoles possess co-catalytic activity greater than that of strong σ-donor amines and weak π-donor pyridines. When electron-deficient Mn(Por)s were employed as catalyst, pyridines demonstrated a higher co-catalytic activity than that of N-H imidazoles. The pronounced effect of protic solvents on the rate and selectivity of oxidation reactions, particularly in the presence of electron-deficient Mn(Por)s has been observed. The outcome of our investigations accompanied by UV-Vis and Raman spectral data confirms the involvement of different active oxidant such as a high valent Mn-oxo species as well as a six-coordinate [(L)(Por)Mn-OHSO₄] complex.     

Covalent Inorganic Azides

The chemistry of covalent inorganic azides originated with the synthesis of aqueous HN₃ solutions by Tony Curtis in 1890. A little later, in 1900, it proved possible to prepare iodine azide, IN₃, as the first member of the meanwhile complete series of halogen azides. Since then it has been possible to synthesize, in addition to HN₃ and the stable salt H₂NSbF, azide compounds of elements from Groups 13 to 17. In these compounds the N₃ moiety acts as a pseudohalogen and is primarily covalently coordinated to the nonmetal. Only a few organic azides, however, as well as HN₃, H₂N, and all halogen azides have been thoroughly studied with respect to structure and bonding. The combined application of diffraction methods (X-ray and electron diffraction) and microwave spectroscopy together with quantum chemical approaches such as ab initio SCF and density functional calculations have led in the last few years to an improved understanding of the molecular properties of numerous nonmetal azides, almost all of which are explosive. This interaction of theory and experiment has greatly enhanced the development of azide chemistry and has led to realistic expectations for the synthesis of as yet unknown nonmetal azides.     

“鱼”乐圈大揭秘

This article introduces the relationship between chemistry and fish farming, fish selling, and fish food. The nitrogen cycle process in fish ponds is introduced to explain the fish farming. "Yufuling" is used as the entry point to fish selling to connect food safety with chemistry. Fishy smell is explained from a chemical perspective for fish food. This paper aims at making a scientific explanation of life phenomena, deepening the consciousness of chemical life, helping people establish a correct view of chemical science, and inspiring youth to learn to use the knowledge that they have learned to explain life phenomena. This paper also tries to show the youth that life cannot be separated from chemistry, and chemistry cannot be separated from life.     

The impact of nitrogen fertilizers on degradation and leaching of chlorotoluron in soil

Abstract

This study presents the developed and applied methods for the determination of carbendazim in environmental samples originating from several field studies.

For water samples sample pretreatment consisted of a solid phase extraction (SPE) on cartridges packed with 200 mg SDB-1. In case of solid samples the performance of microwave assisted solvent extraction (MASE) and classical ultrasonic extraction with acetone-ethyl acetate were studied. The latter technique was selected because of the reduced time of manual operations. Instrumental analysis of extracts of water samples was performed on-line with coupled column reversed phase liquid chromatography (LC/LC) and UV detection (280 nm) allowing to assay carbendazim to a level of at least 0.1 μg/l. Improved column life time was obtained by performing the favorable LC separation of carbendazim at high pH on newly developed 5 μm Extend-pH bidentate C18 material.

The combination of a short column packed with 5 μm Inertsil ODS-5 and a mobile phase at low pH material was most adequate as the regards the robust and fast processing of extracts of solid samples and allowed in most cases the screening of carbendazim in soils and sediments to a level of 10μg/kg.

The developed procedures yield overall recoveries for carbendazim of 101, 80 and 71 % in water (levels, 0.1—1.2 μg/l: n=12), soil (levels, 10 and 100 μg/kg; n=22) and sediments (levels, 10 and 100 μg/kg; n=11), respectively, with a repeatability and reproducibility below 7 % for all method/matrix combinations. Soil samples with aged residues (level, 100 μg/kg; n=10) provided an overall recovery of 71% and no significant decrease of carbendazim was observed during nine weeks of storage in the refrigerator.     

Vapor-liquid equilibria for the nitrogen-isobutane system

Vapor-liquid equilibria have been investigated experimentally for the nitrogen-isobutane system at temperatures from 120 K to 220 K and at pressures up to 150 bar. Below 126.5 K, two liquid phases were observed as pressure was increased to near the vapor pressure of pure nitrogen. The equilibrium ratio of nitrogen in the binary system and the Henry’s law constants for nitrogen in isobutane were determined from experimental data. The experimental phase equilibrium data were correlated by means of the Peng-Robinson equation of state.     

Acetic anhydride mediated condensation of aromatic o-diacid dichlorides with benzimidazoles to provide electro-reducible p-dione adducts

Acetic anhydride mediates a facile and rapid condensation of benzimidazole with aromatic o-diacid dichlorides to precipitate p-dione adducts in excellent yields. Condensation with pyridine-3,4-dicarbonyl dichloride produced a 1:1 mixture of isomeric p-diones. The X-ray crystal structure of one of the latter isomers revealed unusual high density, and inter-layer separation similar to graphite. Cyclic voltammetry demonstrated that p-dione is capable of two consecutive one-electron-reductions with formal potentials influenced by the fused (hetero)aromatic and substituent effects.     

MnOx/SAPO-11催化剂的制备、表征及其低温NH3-SCR活性

分别采用浸渍法、柠檬酸络合法以及沉淀法在SAPO-11分子筛上负载MnO_x,制备了一系列MnO_x/SAPO-11催化剂。考察了催化剂的低温NH₃选择性催化还原(SCR) (NH₃-SCR) NO_x的性能。结果表明,沉淀法制备的负载量为20%(w)的MnO_x/SAPO-11催化剂表现出最优异的低温NH₃-SCR性能及N₂选择性。通过X射线衍射(XRD)、扫描电镜(SEM)、能量散射谱(EDS)、原子吸收光谱(AAS)、N₂吸附-脱附、X射线光电子能谱(XPS)、H₂程序升温还原(H₂-TPR)、NH₃程序升温脱附(NH₃-TPD)以及NO/O₂程序升温脱附-质谱(NO/O₂-TPD-MS)等多种表征手段对催化剂的结构及表面性质进行分析。表征结果显示,采用不同方法制备催化剂时,其表面MnO_x的存在形式和晶相结构不同。沉淀法制备的催化剂表面存在无定型态MnO_x以及MnO₂晶型,具有较大的介孔及外表面积、更多比例的Mn⁴⁺和化学吸附氧,同时表面存在对反应有利的中强酸以及强酸。因此,催化剂在低温SCR反应阶段能够生成重要中间产物NO₂,从而表现出最佳低温活性。同时,三种制备方法均能使MnO_x相对均匀分散在SAPO-11表面。SAPO-11对催化剂表面MnO_x物种的形成具有一定的影响,从而影响催化剂的酸性,拓宽了MnO_x的活性温度窗口,提高了催化剂的N₂选择性。