High Lithium Storage Capacity and Long Cycling Life Fe3S4 Anodes with Reversible Solid Electrolyte Interface Films and Sandwiched Reduced Graphene Oxide Shells

Electron Aggregation and Oxygen Fixation Reinforced Microwave Dynamic and Thermal Therapy for Effective Treatment of MRSA-Induced Osteomyelitis

Antibiotics are frequently used to clinically treat osteomyelitis caused by bacterial infections. However, extended antibiotic use may result in drug resistance, which can be life threatening. Here, a heterojunction comprising Fe2O3/Fe3S4 magnetic composite is constructed to achieve short-term and efficient treat osteomyelitis caused by methicillin-resistant Staphylococcus aureus (MRSA). The Fe2O3/Fe3S4 composite exhibits powerful microwave (MW) absorption properties, thereby effectively converting incident electromagnetic energy into thermal energy. Density functional theory calculations demonstrate that Fe2O3/Fe3S4 possesses significant charge accumulation and oxygen-fixing capacity at the heterogeneous interface, which provides more active sites and oxygen sources for trapping electromagnetic hotspots. The finite element analysis indicates that Fe2O3/Fe3S4 displays a larger electromagnetism field enhancement parameter than Fe2O3 owing to a significant increase in electromagnetic hotspots. These hotspots contribute to charge differential accumulation and depletion motions at the interface, thereby augmenting the release of free electrons that subsequently combine with the oxygen adsorbed by Fe2O3/Fe3S4 to generate reactive oxygen species (ROS) and heat. This research, which achieves extraordinary bacterial eradication through the synergistic effect of microwave thermal therapy (MWTT) and microwave dynamic therapy (MDT), presents a novel strategy for treating deep-tissue bacterial infections.

Facet-Dependent Activation of Oxalic Acid over Magnetic Recyclable Fe3S4 for Efficient Pollutant Removal under Visible Light Irradiation: Enhanced Catalytic Activity, DFT Calculations, and Mechanism Insight

Photo-Fenton-like reaction based on oxalic acid (OA) activation is a promising method for the fast degradation of pollutants due to the low cost and safety. Hence, the magnetic recyclable greigite (Fe₃S₄) with the exposed {011} facet (FS-011) was prepared using a facile one-pot hydrothermal method and activated OA under visible light irradiation for pollutant removal, in which the removal efficiency values of FS-011 for metronidazole (MNZ) and hexavalent chromium were 2.02 and 1.88 times higher than that of Fe₃S₄ with the exposed {112} facet, respectively. Density functional theory calculations revealed that OA was more easily adsorbed by the {011} facet of Fe₃S₄ than by the {112} facet, and the in situ-generated H₂O₂ preferred to diffuse away from the active sites of the {011} facet of Fe₃S₄ than from that of the {112} facet, which was conducive to the continuous adsorption and efficient activation of OA. Moreover, the analyses of Fukui index and dual descriptor confirmed the degradation mechanism that the imidazole ring of MNZ was easy to be attacked by electrophilic species, while the amino group of MNZ was easy to be attacked by nucleophilic species. These findings deeply analyzed the mechanism of enhanced OA activation by facet engineering and consolidated the theoretical basis for practical application of Fenton-like reactions.

Co-Doped Fe3S4 Nanoflowers for Boosting Electrocatalytic Nitrogen Fixation to Ammonia under Mild Conditions

Compared with the Haber Bosch process, the electrochemical nitrogen reduction reaction (NRR) under mild conditions provides an alternative and promising route for ammonia synthesis due to its green and sustainable features. However, the great energy barrier to break the stable N≡N bond hinders the practical application of NRR. Though Fe is the only common metal element in all biological nitrogenases in nature, there is still a lack of study on developing highly efficient and low-cost Fe-based catalysts for N₂ fixation. Herein, Co-doped Fe₃S₄ nanoflowers were fabricated as the intended catalyst for NRR. The results indicate that 4% Co-doped Fe₃S₄ nanoflowers achieve a high Faradaic efficiency of 17% and a NH₃ yield rate of 37.5 μg·h^-1·mg^-1_cat. at -0.55 V versus RHE potential in 0.1 M HCl, which is superior to most Fe-based catalysts. The introduction of Co atoms can not only shift the partial density states of Fe₃S₄ toward the Fermi level but also serve as new active centers to promote N₂ absorption, lowering the energy barrier of the potential determination step to accelerate the catalytic process. This work paves a pathway of the morphology and doping engineering for Fe-based electrocatalysts to enhance ammonia synthesis.

Activate Fe3S4 Nanorods by Ni Doping for Efficient Dye-Sensitized Photocatalytic Hydrogen Production

Developing suitable catalysts capable of receiving injected electrons and possessing active sites for hydrogen evolution reaction (HER) is the key to building an efficient dye-sensitized system for hydrogen production. Fe₃S₄ is generally regarded as an inferior HER catalyst among the metal sulfide family, mainly due to its weak surface adsorption toward H atoms. In this work, we demonstrate a facile metal-organic framework-derived method to synthesize uniform Fe₃S₄ nanorods and active them for HER by Ni doping. Our experimental results and theoretical calculations reveal that Ni doping can greatly modify the electronic structure of Fe₃S₄ nanorods, improving their electron conductivity and optimizing their surface adsorption energy toward H atoms. Sensitized by a commercial organic dye (eosin-Y), 1%Ni-doped Fe₃S₄ nanorods display a high H₂ production rate of 3240 μmol g_cat^-1 h^-1 with an apparent quantum yield of 12% under 500 nm wavelength, which is significantly higher than that of pristine Fe₃S₄ and even higher than that of 1% Pt-deposited Fe₃S₄. The working mechanism of this dye-sensitized system is explored, and the effect of Ni-doping concentration has been studied. This work presents a facile strategy to synthesize metal-doped sulfide nanocatalysts with greatly enhanced activity toward photocatalytic H₂ production.

Facile fabrication of hollow CuO nanocubes for enhanced lithium/sodium storage performance

Facile and low-toxicity fabrication of CuO hollow nanocubes towards high-performance alkali ion batteries.

Achieving High Lithium Storage Capacity and Long-Term Cyclability of Novel Cobalt Germanate Hydroxide/Reduced Graphene Oxide Anodes with Regulated Electrochemical Catalytic Conversion Process of Hydroxyl Groups

To develop ternary transition-metal germanate anodes with superior lithium storage performances for lithium-ion batteries, a novel capacity counterbalance approach in one compound is designed by introducing an electrocatalytic conversion-type component with a positive cycling trend to compensate the negative cycling trend of the GeO₂ component. Novel cobalt germanate hydroxide (CGH) nanoplates chemically bonded on reduced graphene oxide (RGO) sheets are thus synthesized with a mild one-pot hydrothermal approach, constructing maximal face-to-face contact interfaces with interfacial bonds to boost the electrochemical conversion reactions. Furthermore, the hydroxyl groups (Co-OH) of CGH nanoplates are regulated by thermal annealing treatments, thus controlling the capacity contribution resulting from the electrocatalytic conversion reaction of LiOH to exactly offset the capacity fading of GeO₂. The results on the CGH electrodes at different cycling potentials confirm the stepwise electrochemical reactions of Co, GeO₂, and LiOH. The equilibrium of these electrochemical reactions ensures a stable cycling capacity without obvious fluctuations. Consequently, the optimal CGH/RGO hybrid anode delivers a reversible capacity as high as 1136 mA h g^-1 at 0.1 A g^-1 until 100 cycles. It also exhibits a long cyclability with a retained capacity of 560 mA h g^-1 at 1 A g^-1 until 1000 cycles. This work demonstrates a general and efficient capacity counterbalance method to highly boost lithium storage performances in terms of high capacity and long-term cyclability.

Electrostatically Fabricated Three-Dimensional Magnetite and MXene Hierarchical Architecture for Advanced Lithium-Ion Capacitors

Conversion-type magnetite shrewdly shows abundance, nontoxicity, and high lithium storage capacity. However, either pristine magnetite or nanocomposites with two-dimensional materials cannot prevent restacking, pulverization, and poor structural homogeneity simultaneously because of a lack of universal interfacial interactions. Here, an electrostatic self-assembly strategy is uncovered between hollow Fe₃O₄/C microspheres (with H⁺-induced quasi-intrinsic positive charge) and few-layer MXenes (with intrinsic negative charge from terminating functionalities). This strategy realizes the uniform and interconnected architecture of Fe₃O₄/C@MXene that favors fast Li⁺ diffusion, easy electron/charge transfer, and suppressed pulverization. Specifically, after the long-term cycling, an undegraded specific capacity of 907 mA h g^-1 remains at 0.5 A g^-1. Further adoption of such superior anode in 4.0 V lithium-ion capacitors results in a high energy density of 130 W h kg^-1, a maximum power density of 25,000 W kg^-1, and excellent cycling stability. This work thus sheds light on a generic self-assembly process where intrinsic electrostatic interaction plays an essential role.

Synthesis of 3D flower-like Fe3S4 microspheres and quasi-sphere Fe3S4-RGO hybrid-architectures with enhanced electromagnetic wave absorption

3D flower-like Fe3S4 microspheres and quasi-sphere Fe3S4-RGO hybrid-architectures were successfully fabricated by a facile template-free hydrothermal method. The results of morphology revealed that the single Fe3S4 was composed of many nanoflakes and the Fe3S4-RGO composites mainly distributed together into a ball up and down the RGO sheet. The electromagnetic parameters of the single Fe3S4 and Fe3S4-RGO composites could be controlled by adjusting different filler loading and the addition of different GO to achieve impedance matching. Both the single Fe3S4 and Fe3S4-RGO composites exhibited an excellent EM absorption ability. The minimum reflection loss (RL) of the single Fe3S4 with 50% filler loading could achieve -66.87 dB at 10.57 GHz for the thickness of 2.2 mm, and the absorption bandwidth (RL < -10 dB) could reach 3.49 GHz. For the Fe3S4-RGO composites, the minimum RL of FSR-1 could be -40.25 dB at 9.67 GHz with the thickness of 2.0 mm. In addition, the effective absorption bandwidth of FSR-2 could reach 3.85 GHz at only 1.45 mm and the minimum RL was -29.25 dB at 14.24 GHz. Consequently, the single Fe3S4 and Fe3S4-RGO composites are promising materials as a high performance and adjustable EM wave absorber.

Cobalt Hydroxide Carbonate/Reduced Graphene Oxide Anodes Enabled by a Confined Step-by-Step Electrochemical Catalytic Conversion Process for High Lithium Storage Capacity and Excellent Cyclability with a Low Variance Coefficient

Transition metal carbonates/hydroxides have attracted much attention as appealing anode materials due to their considerable reversible electrochemical catalytic conversion capacity. However, their serious positive or negative trends with cycles caused by the electrochemical catalytic conversion seriously affect their practical applications. Herein, novel one-dimensional cobalt hydroxide carbonate (CHC) nanomaterials are tightly anchored on reduced graphene oxide (RGO) sheets via a facile one-pot hydrothermal synthesis, forming surface-confined domains to further restrict the electrochemical catalytic conversion process. The analysis on the cycled electrodes at varied potentials confirms that the added capacity of CHC arises from the step-by-step reversible reactions of Li₂CO₃ and LiOH under the electrochemical catalysis of Co metal generated by the conversion reaction of CHC. The reversible reaction of Li₂CO₃ is followed closely by that of LiOH in the discharge process, while the order is opposite in the charge process. Such a step-by-step electrochemical catalytic conversion process could confine each other to accommodate the volume change and avoid side reactions. The confined effect is further enhanced by limiting the width and length of the CHC, which are determined by regulating the nucleation and growth of CHC on the surface of RGO, leading to an extraordinary cyclability. The optimized CHC/RGO hybrid maintains a high reversible capacity of 1110 mA h g^-1 after 100 cycles at 0.1 A g^-1, which is much higher than the theoretical value of CHC (506 mA h g^-1) on the basis of the recognized conversion reaction. Furthermore, it keeps high reversible capacities of 755 and 506 mA h g^-1 after 200 cycles at 1 and 2 A g^-1, respectively, exhibiting a high-rate cyclability with the lowest coefficient of variance of 9.4% among the reported ones. The confined step-by-step electrochemical catalytic conversion process facilitates high lithium storage capacity and satisfactory cyclability with a pretty low variance coefficient.

In situ synthesis of a Fe3S4/MIL-53(Fe) hybrid catalyst for an efficient electrocatalytic hydrogen evolution reaction

By modulating the Fe₃S₄/MIL-53(Fe) ratio with a controlled partial sulfurization strategy, the Fe₃S₄(52.1 wt%)/MIL-53 hybrid catalyst with an ideal hierarchical nanostructure and composition exhibited high HER activity.

PEDOT-PSS coated VS2 nanosheet anodes for high rate and ultrastable lithium-ion batteries

A high rate and ultrastable anode material is successfully synthesized by encapsulating VS₂ nanosheets into a PEDOT-PSS shell.

Enhanced lithium storage performances of novel layered nickel germanate anodes inspired by the spatial arrangement of lotus leaves

The rapid capacity degradation of Ge-based materials hinders their practical application for next generation lithium ion batteries, which could be solved by synthesizing Ge-containing ternary oxides, with new structures and hybridizing with carbon nanomaterials. Herein, novel Ni3Ge2O5(OH)4 nanosheets were synthesized and distributed in situ on reduced graphene oxide (RGO) sheets, with both flat-lying and vertically-grown spatial distributions to imitate the growth of lotus leaves. These two types of Ni3Ge2O5(OH)4 nanosheets enhance their efficient contact with RGO, and increase the mass loading of active materials. Furthermore, the interfacial bonds between RGO sheets and Ni3Ge2O5(OH)4 nanosheets are introduced to improve the diffusion rate of lithium ions. The RGO sheets act as a buffer matrix to sustain the volume change and prevent the nanosheets from aggregation. Consequently, the chemically bonded Ni3Ge2O5(OH)4/RGO hybrid delivers a high specific capacity of 863 mA h g-1 over 75 cycles, which is much higher than those for neat Ni3Ge2O5(OH)4 nanosheets or the hybrid without the interfacial bonding. This study provides a novel perspective for designing high-performance Ge-based anode materials for advanced lithium ion batteries.

Neuron-Inspired Fe3O4/Conductive Carbon Filament Network for High-Speed and Stable Lithium Storage

Construction of a continuous conductance network with high electron-transfer rate is extremely important for high-performance energy storage. Owing to the highly efficient mass transport and information transmission, neurons are exactly a perfect model for electron transport, inspiring us to design a neuron-like reaction network for high-performance lithium-ion batteries (LIBs) with Fe₃O₄ as an example. The reactive cores (Fe₃O₄) are protected by carbon shells and linked by carbon filaments, constituting an integrated conductance network. Thus, once the reaction starts, the electrons released from every Fe₃O₄ cores are capable of being transferred rapidly through the whole network directly to the external circuit, endowing the nanocomposite with tremendous rate performance and ultralong cycle life. After 1000 cycles at current densities as high as 1 and 2 A g^-1, charge capacities of the as-synthesized nanocomposite maintain 971 and 715 mA h g^-1, respectively, much higher than those of reported Fe₃O₄-based anode materials. The Fe₃O₄-based conductive network provides a new idea for future developments of high-rate-performance LIBs.