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

Facile synthesis of a carbon supported lithium iron phosphate nanocomposite cathode material from metal-organic framework for lithium-ion batteries

Lithium iron phosphate (LiFePO4, LFP) has become one of the most widely used cathode materials for lithium-ion batteries. The inferior lithium-ion diffusion rate of LFP crystals always incurs poor rate capability and unsatisfactory low-temperature performances. To meet with the requirements from the ever-growing market, it is of great significance to synthesize carbon supported LFP nanocomposite (LFP/C) cathode materials using cost effective and environmentally friendly methods. In this work, an LFP/C cathode material is straightforwardly prepared from a metal-organic framework (MOF) precursor ferric gallate (Fe-GA) using its self-template effect. The Fe-GA precursor is firstly fabricated from the redox coprecipitation reaction between Fe foils and gallic acid (GA) molecules in mild aqueous phase. Then the Fe-GA is directly converted to the LFP/C sample after a following solid-state reaction. In half-cells, the LFP/C composite exhibits a reversible capacity of 109.7 mAh·g-1 after 500 cycles under the current rate of 100 mA·g-1 at 25 °C as well as good rate capabilities. In the LFP/C//graphite full-cells, the LFP/C composite can deliver a reversible capacity of 71.4 mAh·g-1 after 50 cycles in the same condition as the half-cells. The electrochemical performances of the LFP/C cathode in half-cells at lower temperature of -10 °C are also examined. Particularly, the evolution of samples has been explored and the lithium-ion storage mechanism of the LFP/C cathode has been unveiled. The sample synthesis protocol is straightforward, eco-friendly and atomic efficient, which can be considered to have good potential for scaling-up.

Rational engineering of a carbon skeleton supported tin dioxide nanocomposite from MOF on graphene precursor for superior lithium and sodium ion storage

Tin dioxide (SnO2) is being investigated as a promising anode material for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). Effectively dispersing small sized SnO2 crystals in well-designed carbonaceous matrices using eco-friendly materials and simplified methods is an urgent task. Herein, gallic acid (GA) molecules, abundant in plant kingdom, are firstly selected to react with few-layered graphene oxide (GO) in mild hydrothermal condition, and the GA modulated reduced graphene oxide (GA@RGO) supporting skeleton can be obtained. Then Sn-GA metal-organic framework (MOF) domains can be directly engineered on the surface of the GA@RGO sheets with controlled size and improved dispersion. Finally, the well-designed Sn-GA@RGO precursor is converted to the SnO2/C/RGO nanocomposite with significantly optimized microstructure. The SnO2/C/RGO sample delivers an excellent specific capacity of 823.6 mAh·g-1 after 700 cycles at 1000 mA·g-1 in half-cells and 741.3 mAh·g-1 after 50 cycles at 200 mA·g-1 in full-cells for LIBs, a specific capacity of 370.3 mAh·g-1 after 600 cycles at 200 mA·g-1 in half-cells for SIBs. The sample preparation strategy is rationally established by comprehensively understanding the interactions between GO sheets, Sn2+ ions and GA molecules, and the engineered SnO2/C/RGO nanocomposite has good prospects in wider fields.

Design and Construction of Carbon-Coated Fe3 O4 /Cr2 O3 Heterostructures Nanoparticles as High-Performance Anodes for Lithium Storage

Transition metal oxides, highly motivated anodes for lithium-ion batteries due to high theoretical capacity, typically afflict by inferior conductivity and significant volume variation. Architecting heterogeneous structures with distinctive interfacial features can effectively regulate the electronic structure to favor electrochemical properties. Herein, an engineered carbon-coated nanosized Fe3 O4 /Cr2 O3 heterostructure with multiple interfaces is synthesized by a facile sol-gel method and subsequent heat treatment. Such ingenious components and structural design deliver rapid Li+ migration and facilitate charge transfer at the heterogeneous interface. Simultaneously, the strong coupling synergistic interactions between Fe3 O4 , Cr2 O3 , and carbon layers establish multiple interface structures and built-in electric fields, which accelerate ion/electron transport and effectively eliminate volume expansion. As a result, the multi-interface heterostructure, as a lithium-ion battery anode, exhibits superior cycling stability maintaining a reversible capacity of 651.2 mAh g-1 for 600 cycles at 2 C. The density functionaltheory calculations not only unravel the electronic structure of the modulation but also illustrate favorable lithium-ion adsorption kinetics. This multi-interface heterostructure strategy offers a pathway for the development of advanced alkali metal-ion batteries.

Phosphate adsorption by metal organic frameworks: Insights from a systematic review, meta-analysis, and predictive modelling with artificial neural networks

This comprehensive study analysed 55 articles published between 2011 and 2022 on the use of metal organic frameworks (MOFs) for phosphate adsorption. The study found that the performance of MOFs in phosphate adsorption is influenced by various factors such as the type of MOF, synthesis method, modification/alteration, and operational conditions (initial concentration, adsorbent dose, pH, contact time, and temperature). Most of the MOFs have a wide range of theoretical maximum adsorption capacity for phosphate, but their long-term use in phosphorus recovery may be limited due to the adsorption mechanisms being dominated by inner sphere complexation. The study employed machine learning to construct artificial neural network (ANN) models for predicting phosphate adsorption capacity based on input features from operation and synthesis procedures. The initial phosphate concentration was the most important input from the operational features, while the modulator agent was consistently relevant during MOF synthesis. The models showed strong fitting for most MOF types recorded for the study, such as UIO-66, MIL-100, ZIF-8, Al-MOFs, La-MOFs, and Ce-MOFs. Overall, this study provides valuable insights for the design of MOF adsorbents for phosphate adsorption and offers guidance for future research in this area.

Ultrasmall iron-gallic acid coordination polymer nanodots with antioxidative neuroprotection for PET/MR imaging-guided ischemia stroke therapy

Oxidative stress from reactive oxygen species (ROS) is a reperfusion injury factor that can lead to cell damage and death. Here, ultrasmall iron-gallic acid coordination polymer nanodots (Fe-GA CPNs) were developed as antioxidative neuroprotectors for ischemia stroke therapy guided by PET/MR imaging. As proven by the electron spin resonance spectrum, the ultrasmall Fe-GA CPNs with ultrasmall size, scavenged ROS efficiently. In vitro experiments revealed that Fe-GA CPNs could protect cell viability after being treated with hydrogen peroxide (H2O2) and displayed the effective elimination of ROS by Fe-GA CPNs, which subsequently restores oxidation balance. When analyzing the middle cerebral artery occlusion model, the neurologic damage displayed by PET/MR imaging revealed a distinct recovery after treatment with Fe-GA CPNs, which was proved by 2,3,5-triphenyl tetrazolium chloride staining. Furthermore, immunohistochemistry staining indicated that Fe-GA CPNs inhibited apoptosis through protein kinase B (Akt) restoration, whereas western blot and immunofluorescence indicated the activation of the nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) pathway following Fe-GA CPNs application. Therefore, Fe-GA CPNs exhibit an impressive antioxidative and neuroprotective role via redox homeostasis recovery by Akt and Nrf2/HO-1 pathway activation, revealing its potential for clinical ischemia stroke treatment.

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.

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.

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.

Comparison of the Surface Properties of Hydrothermally Synthesised Fe3O4@C Nanocomposites at Variable Reaction Times

The influence of variable reaction time (tr) on surface/textural properties (surface area, total pore volume, and pore diameter) of carbon-encapsulated magnetite (Fe3O4@C) nanocomposites fabricated by a hydrothermal process at 190 °C for 3, 4, and 5 h was studied. The properties were calculated using the Brunauer-Emmett-Teller (BET) isotherms data. The nanocomposites were characterised using Fourier transform infrared spectroscopy, X-ray diffraction analysis, thermogravimetry, and scanning and transmission electron microscopies. Analysis of variance shows tr has the largest effect on pore volume (F value = 1117.6, p value < 0.0001), followed by the surface area (F value = 54.8, p value < 0.0001) and pore diameter (F value = 10.4, p value < 0.001) with R2-adjusted values of 99.5%, 88.5% and 63.1%, respectively. Tukey and Fisher tests confirmed tr rise to have caused increased variations in mean particle sizes (11-91 nm), crystallite sizes (5-21 nm), pore diameters (9-16 nm), pore volume (0.017-0.089 cm3 g-1) and surface area (7.6-22.4 m2 g-1) of the nanocomposites with individual and simultaneous confidence limits of 97.9 and 84.4 (p-adj < 0.05). The nanocomposites' retained Fe-O vibrations at octahedral (436 cm-1) and tetrahedral (570 cm-1) cubic ferrite sites, modest thermal stability (37-60 % weight loss), and large volume-specific surface area with potential for catalytic application in advanced oxidation processes.