A Carbonyl and Azo-Based Polymer Cathode for Low-Temperature Na-Ion Batteries

Due to flexible structure tunability and abundant structure diversity, redox-active polymers are promising cathode materials for developing affordable and sustainable Na-ion batteries (NIBs). However, polymer cathodes still suffer from low capacity, poor cycle life, and sluggish reaction kinetics. Herein, we designed and synthesized a polymer cathode material bearing carbonyl and azo groups as well as extended conjugation structures in the repeating units. The polymer cathode exhibited exceptional electrochemical performance in NIBs in terms of high capacity, long lifetime, and fast kinetics. When coupled with a low-concentration electrolyte, it shows superior performance at low temperatures down to -50 °C, demonstrating great promise for low-temperature battery applications. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were employed to study the reaction mechanism, interphase structure, and morphological evolution, confirming reversible redox reactions between azo/carbonyl groups in the polymer and Na+/electrons, a NaF-rich interphase, and high structure stability upon cycling. This work provides an effective approach to developing high-performance polymer cathodes for affordable, sustainable, and low-temperature NIBs.

Cyclic Voltammetry of C.I. Disperse Orange 62 in an Aqueous Electrolyte

Disperse dyes are an important group of colorants for dyeing polyester fibers. Approximately 30.000 tons of disperse dyes are released into the waste water annually from spent dyebaths. Therefore, methods for decolorizing such dyes are of general interest. The reductive after-treatment of disperse dyes using reducing agents, such as Na2S2O4, is a widely used process to improve rub fastness through dye reduction. Electrochemical dye reduction could be an alternative process for reductive dye treatment. In this work C.I. Disperse Orange 62 was used as a representative dye to study the direct cathodic reduction of a disperse dye with cyclic voltammetry. As anticipated for dispersed organic matter, relatively low current densities were observed, which strongly depend on the state of dispersion of the dye. The current density was increased by using dispersions prepared through dye precipitation from DMF solution and by the use of N-cetyl-N,N,N,-trimethyl-ammonium bromide as a cationic surfactant. The results demonstrate the successful cathodic reduction of a dispersed organic dye; however, the low solubility of the reaction products in the aqueous electrolyte hinders an efficient cathodic dye reduction.

Boosting the Energetic Performance of Trinitromethyl-1,2,4-oxadiazole Moiety by Increasing Nitrogen-Oxygen in the Bridge

The trinitromethyl moiety is a useful group for the design and development of novel energetic compounds with high nitrogen and oxygen content. In this work, by using an improved nitration method, the dinitromethyl precursor was successfully nitrated to the trinitromethyl product (2), and its structure was thoroughly characterized by FTIR, NMR, elemental analysis, differential scanning calorimetry, and single-crystal X-ray diffraction. Compound 2 has a high density (1.897 g cm⁻³), high heat of formation (984.8 kJ mmol⁻¹), and a high detonation performance (D: 9351 m s⁻¹, P: 37.46 GPa) that may find useful applications in the field of high energy density materials.

Highly C2/C1-Selective Covalent Organic Frameworks Substituted with Azo Groups

A series of covalent organic frameworks substituted with azo groups (AzoCOFs) have been synthesized via imine condensation. The obtained frameworks show crystallinity and high stability. More importantly, the AzoCOFs exhibit exceptionally high ideal adsorption solution theory (IAST) selectivity in adsorption of C₂H₂ (35-2891) over CH₄ at 273 K and 1 bar, owing to the favorable interactions between azo groups and acetylene molecules. The dependence of the gas adsorption property on pore size and polarity of the frameworks was also studied. The triethylene glycol substituted Tg-AzoCOF shows the highest C₂H₂/CH₄ selectivity (IAST selectivity of 2891), which represents the highest reported for all porous materials. The AzoCOFs also exhibit high IAST adsorption selectivity of C₂H₄/CH₄ (11-20), C₂H₆/CH₄ (15-22), and CO₂/CH₄ (12-37), which is comparable with most porous materials, thus showing their great potential in gas separation applications.

Crystal structure of 5-[2-(2,4,6-tri-bromo-phen-yl)diazen-yl]tropolone

The title compound {systematic name: 2-hy-droxy-5-[2-(2,4,6-tri-bromo-phen-yl)diazen-1-yl]cyclo-hepta-2,4,6-trien-1-one}, C₁₃H₇Br₃N₂O₂, is essentially planar, with an r.m.s. deviation of 0.054 Å. The mol-ecular structure is fixed in the azo tautomer by intra-molecular C-H⋯N inter-actions, with O-H⋯O hydrogen bonds creating linked dimers. Charge-transfer inter-actions are observed, with the segregated stacks linked by Br⋯Br inter-actions.