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.

Rationally engineering a hierarchical porous carbon and reduced graphene oxide supported magnetite composite with boosted lithium-ion storage performances.

Ferric gallate (Fe-GA), an ancient metal-organic framework (MOF) material, has been recently employed as an eco-friendly and cost-effective precursor sample to synthesize a porous carbon confined nano-iron composite (Fe/RPC), and the Fe element in the Fe/RPC sample could be further oxidized to Fe3O4 nanocrystals in a 180 °C hydrothermal condition. On this foundation, this work reports an optimized approach to engineering a hierarchical one-dimensional porous carbon and two-dimensional reduced graphene oxide (RGO) supporting framework with Fe3O4 nanoparticles well dispersed. Under mild hydrothermal condition, the redox reaction between metal iron atoms from Fe/RPC and surface functional radicals from few-layered graphene oxide sheets (GO) is triggered. As a result, reinforced microstructure and improved atomic efficiency have been achieved for the Fe3O4@RPC/RGO sample. The homogeneously dispersed Fe3O4 nanoparticles with controlled size are anchored on the surface of the larger sized RGO coating layers while the smaller sized RPC domains are embedded between the RGO sheets as spacer. Challenges including spontaneous aggregation of RPC, over exposure of Fe3O4 nanoparticles and excessive restacking of RGO have been significantly inhibited. Furthermore, micro-sized carbon fiber (CF) is chosen as a structural reinforcement additive during electrode fabrication, and the Fe3O4@RPC/RGO sample delivers a good specific capacity of 1170.5 mAh·g-1 under a current rate of 1000 mA·g-1 for 500 cycles in the half cell form. The reasons for superior electrochemical behaviors have been revealed and the lithium-ion storage performances of the Fe3O4@RPC/RGO sample in the full cell form have been preliminarily investigated.

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.

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.

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.

Spray drying induced engineering a hierarchical reduced graphene oxide supported heterogeneous Tin dioxide and Zinc oxide for Lithium-ion storage.

In this work, a hierarchical reduced graphene oxide (RGO) supportive matrix consisting of both larger two-dimensional RGO sheets and smaller three-dimensional RGO spheres was engineered with ZnO and SnO2 nanoparticles immobilized. The ZnO and SnO2 nanocrystals with controlled size were in sequence engineered on the surface of the RGO sheets during the deoxygenation of graphene oxide sample (GO), where the zinc-containing ZIF-8 sample and metal tin foil were used as precursors for ZnO and SnO2, respectively. After a spray drying treatment and calcination, the final ZnO@SnO2/RGO-H sample was obtained, which delivered an outstanding specific capacity of 982 mAh·g-1 under a high current density of 1000 mA·g-1 after 450 cycles. Benefitting from the unique hierarchical structure, the mechanical strength, ionic and electric conductivities of the ZnO@SnO2/RGO-H sample have been simultaneously promoted. The joint contributions from pseudocapacitive and battery behaviors in lithium-ion storage processes bring in both large specific capacity and good rate capability. The industrially mature spray drying method for synthesizing RGO based hierarchical products can be further developed for wider applications.

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.

Engineering tin dioxide quantum dots in a hierarchical graphite and graphene oxide framework for lithium-ion storage.

The spontaneous aggregation and poor electronic conductivity are widely recognized as the main challenges for practically applied nano-sized tin dioxide-based anode candidates in lithium-ion batteries. This work describes a hierarchical graphite and graphene oxide (GO) framework stabilized tin dioxide quantum dot composite (SnO2@C/GO), which is synthesized by a solid-state ball-milling treatment and a water-phase self-assembly process. Characterization results demonstrate the engineered inside nanostructured graphite and outside GO layers from the SnO2@C/GO composite jointly contribute to a good immobilization effect for the SnO2 quantum dots. The hierarchical carbonaceous matrix supported SnO2 quantum dots could maintain good structure stability over a long cycling life under high current densities. As an anodic electrochemically active material for lithium-ion batteries, the SnO2@C/GO composite shows a high reversible capacity of 1156 mAh·g-1 at the current density of 1000 mA·g-1 for 350 continual cycles as well as good rate performance. The large pseudocapacitive behavior in this electrode is favorable for promoting the lithium-ion storage capability under higher current densities. The whole synthetic route is simple and effective, which probably has good potential for further development to massively fabricate high-performance electrode active materials for energy storage.

Facile synthesis of a rod-like porous carbon framework confined magnetite nanoparticle composite for superior lithium-ion storage.

This work demonstrates a streamlined method to engineer a rod-like porous carbon framework (RPC) confined magnetite nanoparticles composite (Fe3O4/RPC) starting from metallic iron and gallic acid (GA) solution. First, a mild redox reaction was triggered between Fe and GA to prepare a rod-shaped metal-organic framework (MOF) ferric gallate sample (Fe-GA). Then, the Fe-GA sample was calcinated to obtain a prototypic RPC supported metal iron nanoparticle intermediate sample (Fe/RPC). Finally, the Fe3O4/RPC composite was synthesized after a simple hydrothermal reaction. The Fe3O4/RPC composite exhibited competitive electrochemical behaviors, which has a high gravimetric capacity of 1140 mAh·g-1 at a high charge and discharge current of 1000 mA·g-1 after 300 cycles. The engineered RPC supportive matrix not only offers adequate voids to buffer the volume expansion from inside well-dispersed Fe3O4 nanoparticles, but also facilitates both the ionic and electronic transport during the electrochemical reactions. The overall material synthesis involves of no hazardous or expensive chemicals, which can be regarded to be a scalable and green approach. The obtained samples have a good potential to be further developed for wider applications.

Hierarchical goethite nanoparticle and tin dioxide quantum dot anchored on reduced graphene oxide for long life and high rate lithium-ion storage.

The synergetic effect between two or more electrochemically active materials usually leads to superior lithium-ion storage performance. This work demonstrates a straightforward and effective approach to synthesize a reduced graphene oxide (RGO) encapsulated larger goethite (FeOOH) nanoparticles and smaller tin dioxide (SnO2) quantum dots hierarchical composite (SnO2@FeOOH/RGO). The synthesized SnO2@FeOOH/RGO composite exhibits encouraging lithium-ion storage capability than controlled SnO2/RGO and FeOOH/RGO samples with a stable specific capacity of 638 mAh·g-1 under a high current rate of 1000 mA·g-1 for 2000 continual cycles and good rate performance. The redox reaction between reductive metal-atoms or metal-ions and graphene oxide (GO) sheets guarantees an effective immobilization of corresponding nano-sized metal oxide and hydroxide crystals by the RGO framework. Furthermore, the engineered larger FeOOH crystals engage in lithium-ion storage and perform an ideal spacer between the restacked RGO sheets. Therefore, smaller SnO2 quantum dots' inherent excellent rate capability is extensively promoted due to the improvement of electrolyte diffusion and electron transfer condition. The sample design and fabrication method in this work might be developed for broader applications.

Engineering zinc ferrite nanoparticles in a hierarchical graphene and carbon nanotube framework for improved lithium-ion storage.

This work presents the successful fabrication of a composite made of multi-walled carbon nanotubes and reduced graphene oxide, with immobilized zinc ferrite nanoparticles (ZnFe2O4@CNT/RGO). Functionalized CNT (F-CNT) and few-layered graphene oxide (GO) not only works as a precursor for the hierarchical CNT/RGO skeleton, but also participates in the redox reactions with zinc and ferrous ions to synthesize the intermediate products ZnO@CNT and FeOOH@RGO, respectively. A ZnO@CNT/FeOOH@RGO composite is obtained by through the spontaneous assembly process between the above intermediate species, and the final ZnFe2O4@CNT/RGO composite is fabricated through a simple solid-state reaction. The ZnFe2O4@CNT/RGO composite delivers a reversible capacity of about 1250 mAh·g-1 after 100 cycles at a low current of 200 mA·g-1, about 1100 mAh·g-1 after 300 cycles at a high current of 1000 mA·g-1. It has been verified that an increase in battery performance can be attributed to the engineered hierarchical CNT/RGO supportive skeleton, the generation of smaller electrochemically active ZnO and Fe2O3 crystals, and pseudocapacitive behavior. The sample design and preparation method in this work are both economical and scalable, allowing further development and use in other applications.