Bio-dissolution process and mechanism of copper phosphate hybrid nanoflowers by Pseudomonas aeruginosa and its bacteria-toxicity in life cycle

Copper phosphate hybrid nanoflowers (HNF) have been widely used in chemical industries and wastewater treatment owing to its excellent catalytic activity and high stability. However, their fate and ecological risks have not received due attention after being discharged into natural environment. The significance of bacteria on the dissolution and fate of HNF and its toxicity to bacteria was evaluated from the perspective of its life cycle. Results showed that in the presence of Pseudomonas aeruginosa, HNF was gradually 'disassembled' into smaller nanoparticles (NPs), and then dissolved completely. More than half of the dissolution products (Cu²⁺) entered biological phase, and PO₄^3- was absorbed and utilized by bacteria as a phosphorus source. The mechanisms of HNF bio-dissolution are as follows: the metabolites of bacteria dissolve HNF through complexation and acidification, in which small molecular organic acids and amino acids play an important role. Bacteria toxicity experiments of HNF in its cycle life show that HNF exhibits lower cell toxicity, but its intermediate (smaller NPs) and final dissolved products (Cu²⁺) exhibit stronger cytotoxicity by increasing the level of intracellular ROS and membrane permeability of bacteria. This research is helpful to provide ecological risk assessment, develop targeted applications, and rationally design future nanomaterials.

Aluminum-doping-based method for the improvement of the cycle life of cobalt-nickel hydroxides for nickel-zinc batteries

The unsatisfactory cycle life of nickel-based cathodes hinders the widespread commercial usage of nickel-zinc (Ni-Zn) batteries. The most frequently used methods to improve the cycle life of Ni-based cathodes are usually complicated and/or involve using organic solvents and high energy consumption. A facile process based on the hydrolysis-induced exchange of the cobalt-based metal-organic framework (Co-MOF) was developed to prepare aluminum (Al)-doped cobalt-nickel double hydroxides (Al-CoNiDH) on a carbon cloth (CC). The entire synthesis process is highly efficient, energy-saving, and has a low negative impact on the environment. Compared to undoped cobalt-nickel double hydroxide (Al-CoNiDH-0%), the as-prepared Al-CoNiDH as the electrode material displays a remarkably improved cycling stability because the Al-doping successfully depresses the transition in the crystal phase and microstructure during the long cycling. Benefiting from the improved performance of the optimal Al-CoNiDH electrode (Al-CoNiDH-5% electrode), the as-constructed aqueous Ni-Zn battery with Al-CoNiDH-5% as the cathode (Al-CoNiDH-5%//Zn) displays more than 14% improvement in the cycle life relative to the Al-CoNiDH-0%//Zn battery. Moreover, this Al-CoNiDH-5%//Zn battery achieves a high specific capacity (264 mAh g^-1), good rate capability (72.4% retention at a 30-fold higher current), high electrochemical energy conversion efficiency, superior fast-charging ability, and strong capability of reversible switching between fast charging and slow charging. Furthermore, the as-assembled quasi-solid-state Al-CoNiDH-5%//Zn battery exhibits a decent electrochemical performance and satisfactory flexibility.

Delicate Structural Control of Si-SiOx-C Composite via High-Speed Spray Pyrolysis for Li-Ion Battery Anodes

Despite the high theoretical capacity, silicon (Si) anodes in lithium-ion batteries have difficulty in meeting the commercial standards in various aspects. In particular, the huge volume change of Si makes it very challenging to simultaneously achieve high initial Coulombic efficiency (ICE) and long-term cycle life. Herein, we report spray pyrolysis to prepare Si-SiO_x composite using an aqueous precursor solution containing Si nanoparticles, citric acid, and sodium hydroxide (NaOH). In the precursor solution, Si nanoparticles are etched by NaOH with the production of [SiO₄]^4-. During the dynamic course of spray pyrolysis, [SiO₄]^4- transforms to SiO_x matrix and citric acid decomposes to carbon surface layer with the assistance of NaOH that serves as a decomposition catalyst. As a result, a Si-SiO_x composite, in which Si nanodomains are homogeneously embedded in the SiO_x matrix with carbon surface layer, is generated by a one-pot process with a residence time of only 3.5 s in a flow reactor. The optimal composite structure in terms of Si domain size and Si-to-O ratio exhibited excellent electrochemical performance, such as reversible capacity of 1561.9 mAh g^-1 at 0.06C rate and ICE of 80.2% and 87.9% capacity retention after 100 cycles at 1C rate.