Chitosan modulated engineer tin dioxide nanoparticles well dispersed by reduced graphene oxide for high and stable lithium-ion storage.

Tin based materials are widely investigated as a potential anode material for lithium-ion batteries. Effectively dispersing SnO2 nanocrystals in carbonaceous supporting skeleton using simplified methods is both promising and challenging. In this work, water soluble chitosan (CS) chains are employed to modulate the redox coprecipitation reaction between stannous chloride (SnCl2) and few-layered graphene oxide (GO), where the excessive restacking of the corresponding reduced graphene oxide sheets (RGO) has been effectively inhibited and the grain size of the in-situ formed SnO2 nanoparticles have been significantly controlled. In particular, the CS molecules are gradually detached from the RGO sheets with the GO deoxygenation process, leaving only a small quantity of CS remnants in the intermediate SnO2@CS@RGO sample. The final SnO2/CSC/RGO sample with significantly improved microstructure is synthesized after a simple thermal treatment, which delivers a high specific capacity of 842.9 mAh g-1 at 1000 mA·g-1 for 1000 cycles in half cells and a specific capacity of 410.5 mAh g-1 at 200 mA·g-1 for 100 cycles in full cells. The reasons for the good lithium-ion storage performances for the SnO2/CSC/RGO composite have been studied.

Engineering a hierarchical carbon supported magnetite nanoparticles composite from metal organic framework and graphene oxide for lithium-ion storage.

Fe based metal organic framework (MOF) materials are being extensively investigated as a precursor sample for engineering carbon supported iron containing nanoparticles composites. Rational design and engineering Fe-containing MOFs with optimized structures using economic and eco-friendly methods is a challenging task. In this work, 1,3,5-benzenetricarboxylic acid (C9H6O6, trimesic acid, H3BTC) and metal Fe are employed to synthesize a MOF sample Fe-BTC in a mild hydrothermal condition. Moreover, with the addition of a small quantity of graphene oxide (GO) as dispersant, a redox coprecipitation reaction has taken place where small Fe-BTC domains well dispersed by reduced graphene oxide (RGO). The Fe-BTC/RGO intermediate sample is finally converted to the hierarchical Fe3O4@C/RGO composite, which delivers an ultrahigh specific capacity of 1262.61 mAh·g-1 at 200 mA·g-1 after 150 cycles and a superior reversible capacity of 910.65 mAh·g-1 at 1000 mA·g-1 after 300 cycles in half cells. The full cell performance for the Fe3O4@C/RGO composite have been studied. It is also revealed that the improved structural stability, high pseudocapacitive contribution and enhanced lithium-ion and electron transportation conditions jointly guarantee the outstanding lithium-ion storage performances for the Fe3O4@C/RGO composite over long-time cycling. The synthesized samples have good potential for wider application.

Controllable engineering magnetite nanoparticles dispersed in a hierarchical amylose derived carbon and reduced graphene oxide framework for lithium-ion storage.

A straightforward and eco-friendly method is demonstrated to engineer magnetite (Fe3O4) nanoparticles well dispersed by an amorphous amylose-derived carbon (AMC) and reduced graphene oxide (RGO) framework. Naturally available amylose (AM) serves as both reducing agent for few-layered graphene oxide (GO) in the first mild redox coprecipitation system and precursor for small-sized pyrolytic AMC in the following thermal treatment. In particular, the presence of the AM molecules effectively limits the crystal growth kinetics for the akaganeite (FeOOH) in the intermediate FeOOH@AM/RGO sample, which contributes to the transformation to Fe3O4 nanoparticles with significantly controlled size in the final Fe3O4@AMC/RGO composite. As a result, both Fe3O4 nanoparticles and AMC domains are adjacently anchored on the larger sized RGO sheets, and a unique hierarchical structure has been engineered in the Fe3O4@AMC/RGO sample. Compared with the controlled Fe3O4@RGO sample, the Fe3O4@AMC/RGO composite exhibits remarkably enhanced initial coulombic efficiency, superior cycling stability and rate performance for lithium-ion storage. The mechanisms of the interaction between GO sheets and AM molecules as well as the inspiring electrochemical behaviors of the Fe3O4@AMC/RGO electrode have been revealed. The Fe3O4@AMC/RGO sample possesses good potential for scaling-up and finding applications in wider fields.

One-Step Engineering Carbon Supported Magnetite Nanoparticles Composite in a Submicron Pomegranate Configuration for Superior Lithium-Ion Storage.

In this work, magnetite nanoparticles (Fe3O4) that are well dispersed by a submicron sized carbon framework in a pomegranate shape are engineered using a flexible one-step spray pyrolysis strategy. Under inert gas atmosphere, the homogeneously mixed Fe3+ ions and chitosan (CS) molecules are in situ transformed to Fe3O4 nanoparticles and spherical nitrogen-doped carbon coating domains, respectively. Moreover, the obtained Fe3O4@C composite exhibits a unique submicron sized pomegranate configuration, in which favorable electric/ionic pathways have been constructed and the Fe3O4 nanoparticles have been effectively dispersed. When used as an anode electrochemical active material, the Fe3O4@C composite exhibits impressive lithium-ion storage capabilities, and maintains a reversible capacity of 500.2 mAh·g-1 after 500 cycles at a high current density of 1000 mA·g-1 as well as good rate capability. The strategy in this work is straightforward and effective, and the synthesized Fe3O4@C material has good potential in wider applications.

Sodium carboxymethylcellulose induced engineering a porous carbon and graphene immobilized magnetite composite for lithium-ion storage.

Immobilizing nanosized electrochemically active materials with supportive carbonaceous framework usually brings in improved lithium-ion storage performance. In this work, magnetite nanoparticles (Fe3O4) are stabilized by both porous carbon domains (PC) and reduced graphene oxide sheets (RGO) to form a hierarchical composite (Fe3O4@PC/RGO) via a straightforward approach. The PC confined iron nanoparticle intermediate sample (Fe@PC) was first fabricated, where sodium carboxymethylcellulose (Na-CMC) was employed not only as a cross-linker to trap ferric ions for synthesizing a Fe-CMC precursor sample, but also as the carbon source for PC domains and iron source for Fe nanoparticles in a pyrolysis process. The final redox reaction between Fe@PC and few-layered graphene oxide (GO) sheets contributed to the formation of Fe3O4 nanoparticles with reduced size, avoiding any severe aggregation or excessive exposure. The Fe3O4@PC/RGO sample delivered a specific capacity of 522.2 mAh·g-1 under a current rate of 1000 mA·g-1 for 650 cycles. The engineered Fe@PC and Fe3O4@PC/RGO samples have good prospects for application in wider fields.

Zn-doped Tin monoxide nanobelt induced engineering a graphene and CNT supported Zn-doped Tin dioxide composite for Lithium-ion storage.

In this work, a rapid coprecipitation reaction is developed to obtain nano-sized Zn-doped tin oxide samples (Zn-SnO-II or Zn-SnO2-IV) for the first time by simply mixing tin ion (Sn2+ or Sn4+) and zinc ion (Zn2+) containing salts in a mild aqueous condition. Characterization results illustrate the Zn-SnO-II sample is constituted by an overwhelming quantity of Zn-doped SnO nanobelts and a small quantity of Zn-doped SnO2 nanoparticles. The redox reaction between the Sn2+ ions from the Zn-SnO-II sample and the surface oxygen-containing functional groups from functionalized carbon nanotube (F-CNT) and graphene oxide (GO) leads to the formation of the final Zn-SnO2/CNT@RGO composites. As an anode active material for lithium-ion batteries, the Zn-SnO2/CNT@RGO product showed superior electrochemical performance than the controlled Zn-SnO2/CNT and Zn-SnO2/RGO samples, which had a high gravimetric capacity of 901.3 mAh·g-1 at a high charge and discharge current of 1000 mA·g-1 after 300 cycles and excellent rate capability. The reaction mechanism for the successful synthesis of the Zn-doped tin oxide samples has been proposed, and the insight into the outstanding lithium-ion storage performance for the Zn-SnO2/CNT@RGO composite has been revealed. The synthetic processes for both the Zn-doped tin oxides and derived carbon supported composites are straightforward and involve no harsh conditions nor complicated treatment, which have good potential for massive production and application in wider fields.

Heterogeneous iron oxide nanoparticles anchored on carbon nanotubes for high-performance lithium-ion storage and fenton-like oxidation.

In this work, heterogeneous hematite (Fe2O3) and magnetite (Fe3O4) nanoparticles are jointly engineered on the external surface of multi-walled carbon nanotubes (CNTs) to construct a composite material (Fe2O3@Fe3O4/CNT). A simple one-step redox reaction is triggered in a hydrothermal reaction system containing functionalized CNT (FCNT) aqueous suspension and iron foils. Both Fe2O3 and Fe3O4 nanoparticles with controlled size are generated and well dispersed in the interconnected CNT framework. Controlled samples of Fe2O3@Fe3O4 and Fe3O4/CNT have also been prepared and used to investigate the synthetic mechanism and evaluate the lithium-ion storage performances. As an anodic active material for lithium-ion batteries, the Fe2O3@Fe3O4/CNT composite delivered a high reversible capacity of about 924 mAh·g-1 for 200 continual charge/discharge cycles under a high current rate of 1000 mA·g-1. As a catalyst in a Fenton-like reaction for degrading methyl orange (MO) contaminant in waterbody, the Fe2O3@Fe3O4/CNT composite exhibited an attractive decomposition efficiency (99.5% decomposition within 60 min) and good stability. The beneficial factors contributing to the inspiring performances are discussed. The effective and scalable material design and synthesis method can be regarded to have good potential in other fields.