Two-dimensional/three-dimensional hierarchical self-supporting potassium ammonium vanadate@MXene hybrid film for superior performance aqueous zinc ion batteries.

Currently, aqueous zinc ion batteries (AZIBs) have grown to be a good choice for large-scale energy storage systems due to their high theoretical specific capacity, low redox potential, low cost, and non-toxicity of the aqueous electrolyte. However, it is still challenging to obtain high specific capacity and stability suitable cathodes. Herein, hierarchical self-supporting potassium ammonium vanadate@MXene (KNVO@MXene) hybrid films were prepared by vacuum filtration method. Due to the three-dimensional nanoflower structure of KNVO with dual ions intercalation, high conductivity of two-dimensional Ti3C2Tx MXene, and the hierarchical self-supporting structure, the AZIB based on the KNVO@MXene hybrid film cathode possessed superior specific capacity (481 mAh/g at 0.3 A/g) and cycling stability (retaining 125 mAh/g after 1000 cycles at a high current density of 10 A/g). In addition, the storage mechanism was revealed by various ex-situ characterizations. Hence, a new viewpoint for the preparation of AZIB self-supporting cathode materials is presented.

Freestanding defective ammonium Vanadate@MXene hybrid films cathode for high performance aqueous zinc ion batteries.

Aqueous zinc ion batteries (AZIBs) have gained extensive attention due to the numerous advantages of zinc, such as low redox potential, high abundance, low cost as well as high theoretical specific capacity. However, the development of AZIBs is still hampered due to the lack of suitable cathodes. In this work, the freestanding defective ammonium vanadate@MXene (d-NVO@MXene) hybrid film was synthesized by simple vacuum filtration strategy. Due to the presence of the hierarchical freestanding structure, outstanding MXene conductive networks and abundant oxygen vacancy (in the d-NVO nanoribbons), the d-NVO@MXene hybrid film can not only expose more active sites but also possess outstanding conductivity and kinetics of charge transfer/ion diffusion. When the d-NVO@MXene hybrid film was directly used as the cathode, it displayed a high specific capacity of 498 mAh/g at 0.5 A/g and superior cycling stability performance with near 100 % coulomb efficiency. Furthermore, the corresponding storage mechanism was elucidated by ex situ various characterizations. This work provides new ideas for the development of freestanding vanadium-based cathode materials for AZIBs.

Facile and effective defect engineering strategy boosting ammonium vanadate nanoribbon for high performance aqueous zinc-ion batteries.

Vanadium-based oxides have gained widespread attention as promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to their abundant valences, high theoretical capacity and low cost. However, the intrinsic sluggish kinetics and unsatisfactory conductivity have severely hampered their further development. Herein, a facile and effective defect engineering strategy was developed at room temperature to prepare the defective (NH4)2V10O25·8H2O (d-NHVO) nanoribbon with plenty of oxygen vacancies. Owing to the introduction of oxygen vacancies, the d-NHVO nanoribbon possessed more active sites, excellent electronic conductivity and fast ion diffusion kinetics. Benefiting from these advantages, the d-NHVO nanoribbon as an aqueous zinc-ion battery cathode material exhibited superior specific capacity (512 mAh g-1 at 0.3 A g-1), excellent rate capability and long-term cycle performance. Simultaneously, the storage mechanism of the d-NHVO nanoribbon was clarified via comprehensive characterizations. Furthermore, the pouch battery based on the d-NHVO nanoribbon was fabricated and presented eminent flexibility and feasibility. This work provides a novel thought for simple and efficient development of high- performance vanadium-based oxides cathode materials for AZIBs.

Crystallization and preliminary X-ray study of alanine dehydrogenase from Bacillus pseudofirmus OF4.

Alanine dehydrogenase (OF4Ald) from the alkaliphilic Bacillus pseudofirmus OF4 was expressed and purified with a His6 tag in a form suitable for X-ray crystallographic analysis. Crystals were grown by the hanging-drop vapour-diffusion method at 289 K using a solution consisting of 0.1 M Tris-HCl pH 8.0, 0.2 M LiSO4, 22%(w/v) PEG 3350. X-ray diffraction data were collected to 2.8 Šresolution. The crystal belonged to the triclinic space group P1, with unit-cell parameters a = 88.04, b = 105.59, c = 120.53 Å, α = 88.37, ß = 78.77, γ = 82.65°.