Zishun Li

Carbon sphere@Co9S8 yolk-shell structure with good morphology stability for improved lithium storage performance

The poor electronic conductivity and huge volume expansion of cobalt sulfides upon cycling would lead to their poor electrochemical performances for Lithium-ion batteries. Here, we rationally design a yolk-shell carbon sphere@Co9S8 (C@CS) composite, which demonstrates improved kinetics and excellent morphology stability during cycling. This structure can keep Co9S8 shell from collapse and aggregation. After cycling, a layer of thin solid electrolyte interphase is coated on the Co9S8 shells and prevented them from dissolving in electrolyte, which is helpful for the electrochemical performances. As a result, the C@CS electrodes exhibit good lithium storage performances, including excellent cyclic stability up to 300 cycles at 1000 and 2000 mA g-1 and high-rate property of 4000 mA g-1 with a capacity of 489 mA h g-1.

Fabrication of novel sandwich nanocomposite as an efficient and regenerable adsorbent for methylene blue and Pb (II) ion removal

An adsorbent, which is easy to be separated and reused after adsorption, is very important for the removal of pollutants in aqueous solution. Hence, a novel nanofibrous sandwich structured adsorbent of silica nanofiber/magnetite nanoparticles/porous silica (SNF/MNP/PS) was designed and synthesized for the first time. The magnetite nanoparticles with diameter less than 10 nm were evenly distributed on the surface of silica nanofiber, which was subsequently fully covered by a layer of porous silica. The novel adsorbent was proved possessing good adsorption capacity for both methylene blue (MB) and Pb (II) ion (Pb2+), and the adsorption equilibrium could be well described by the Langmuir-isotherm model with the maximum adsorption capacity of 103.1 mg/g for MB and 243.9 mg/g for Pb2+ at 288 K. Moreover, in MB-Pb2+ mixed system the measured adsorption capacity reached 74.5 mg/g for MB and 202.4 mg/g for Pb2+, respectively. The saturated adsorbent could be readily magnetically separated from the solution and then efficiently regenerated by heterogeneous Fenton-like reaction (for MB) or acidic desorption process (for Pb2+), respectively. After 5 cycles of adsorption-regeneration, the adsorption capacity of the reused adsorbent still reached 81.0% (for MB) and 70.9% (for Pb2+) of the initial value. The SNF/MNP/PS behaves good adsorption properties for different types of pollutants, high magnetic recoverability and regeneration efficiency, which make it applicable to different contaminants removal.

Synthesis of a MnO2/Fe3O4/diatomite nanocomposite as an efficient heterogeneous Fenton-like catalyst for methylene blue degradation

Heterogeneous Fenton-like catalysts with the activation of peroxymonosulfate (PMS), which offer the advantages of fast reaction rate, wide functional pH range and cost efficiency, have attracted great interest in wastewater treatment. In this study, a novel magnetic MnO2/Fe3O4/diatomite nanocomposite is synthesized and then used as heterogeneous Fenton-like catalyst to degrade the organic pollutant methylene blue (MB) with the activation of PMS. The characterization results show that the Fe3O4 nanoparticles and nanoflower-like MnO2 are evenly distributed layer-by-layer on the surface of diatomite, which can be readily magnetically separated from the solution. The as-prepared catalyst, compared with other Fenton-like catalysts, shows a superb MB degradation rate of nearly 100% in 45 min in the pH range of 4 to 8 and temperature range of 25 to 55 °C. Moreover, the nanocomposite shows a good mineralization rate of about 60% in 60 min and great recyclability with a recycle efficiency of 86.78% after five runs for MB. The probable mechanism of this catalytic system is also proposed as a synergistic effect between MnO2 and Fe3O4.

Metal organic frameworks derived cobalt sulfide/reduced graphene oxide composites with fast reaction kinetic and excellent structural stability for sodium storage

We report a metal-organic framework-derived Co9S8 nanoflakes on reduced graphene oxide sheet composites as an advanced sodium-ion battery anode. Using a galvanostatic intermittent titration technique, we reveal that the sodium diffusion coefficient of the composite is higher than that of its counterpart. Ex-situ scanning electron microscopy images suggest the excellent mechanical stability of Co9S8 nanoflakes on the reduced graphene oxide sheet electrode during cycling, thereby facilitating cyclic stability. The partial surface-induced capacitive effect also contributes to electrochemical performance. With the reduced graphene oxide, the Co9S8 nanoflakes on the reduced graphene oxide sheet electrode deliver a high discharge capacity of 551 mA h g-1 at 0.1 A g-1, a good rate capability at 10 A g-1, and an excellent cyclic stability up to 500 cycles. rGO/Co9S8 shows potential for practical applications in Na3V2(PO4)3‖rGO/Co9S8 full cells.