L-Cysteine-Assisted Synthesis of Cubic Pyrite/Nitrogen-Doped Graphene Composite as Anode Material for Lithium-ion Batteries

The construction of NiFeSx/g-C3N4 composites with high photocatalytic activity towards the degradation of refractory pollutants

In this work, a novel NiFe layered double hydroxide-derived sulfide (NiFeSx)-modified g-C3N4 nanosheet photocatalyst (NiFeSx/g-C3N4) was synthesized, and its morphology, structure and visible light absorption capacity were simultaneously characterized by XRD, SEM, TEM, FT-IR, XPS, UV-Vis DRS, PL techniques and EIS Nyquist plots. Furthermore, it was discovered that at an optimum mass ratio of 3% (NiFeSx to g-C3N4), 3% NiFeSx/g-C3N4 composites exhibited the best degradation efficiency toward tetracycline hydrochloride refractory pollutants. The degradation rate of tetracycline hydrochloride by 3% NiFeSx/g-C3N4 composites was 92.54% under 70 min of visible light illumination, which was about 2.61 times higher than that of pure g-C3N4. The improved degradation activity may be attributed to the synergistic effect between the two constituents of as-synthesized composites, and the formed heterojunction reduced the efficiency of photogenerated carriers. More importantly, this work also gives some inspiration to synthesize some similar photocatalysts for a targeted environmental remediation.

A multifunctional Ni-doped iron pyrite/reduced graphene oxide composite as an efficient counter electrode for DSSCs and as a non-enzymatic hydrogen peroxide electrochemical sensor

Nickel-doped FeS₂/rGO composites were synthesized as multifunctional materials via a facile hydrothermal method. The synthesized materials were characterized with XRD, FESEM, XPS, and TEM-SAED for structural, morphological and chemical studies. To study their electrochemical properties, all the synthesized composites were subjected to cyclic voltammetry tests. The optimum composite revealed high catalytic activity with high peak current density, limiting current, and efficiency of 7.60% for DSSC, which surpassed that of a platinum-based counter electrode (6.69%). The efficiency of the DSSC was significantly supported by interfacial studies and electron lifetime studies, and it exhibited lower charge transfer resistance and higher electron lifetime, respectively. Moreover, the fabricated DSSCs with high efficiency were subjected to transient photo-response studies and showed a stable current response with multiple photo-ON and OFF cycles for a period of 600 s. To broaden the application of the synthesized material, it was used as an electrochemical sensor for the efficient sensing of hydrogen peroxide (H₂O₂). The sensing electrode was modified with the optimum Ni-doped FeS₂/rGO composite, and voltammetric detection was carried out in the hydrogen peroxide concentration range of 4-100 μM. Thus, the synthesized material can be applied in DSSCs and as an electrochemical H₂O₂ sensor.

Facile Synthesis of FeS@C Particles Toward High-Performance Anodes for Lithium-Ion Batteries

High energy density batteries with high performance are significantly important for intelligent electrical vehicular systems. Iron sulfurs are recognized as one of the most promising anodes for high energy density lithium-ion batteries because of their high theoretical specific capacity and relatively stable electrochemical performance. However, their large-scale commercialized application for lithium-ion batteries are plagued by high-cost and complicated preparation methods. Here, we report a simple and cost-effective method for the scalable synthesis of nanoconfined FeS in porous carbon (defined as FeS@C) as anodes by direct pyrolysis of an iron(III) p-toluenesulfonate precursor. The carbon architecture embedded with FeS nanoparticles provides a rapid electron transport property, and its hierarchical porous structure effectively enhances the ion transport rate, thereby leading to a good electrochemical performance. The resultant FeS@C anodes exhibit high reversible capacity and long cycle life up to 500 cycles at high current density. This work provides a simple strategy for the mass production of FeS@C particles, which represents a critical step forward toward practical applications of iron sulfurs anodes.

Bifunctional iron disulfide nanoellipsoids for high energy density supercapacitor and electrocatalytic oxygen evolution applications

FeS₂, prepared using a rapid microwave assisted method, exhibits excellent electrochemical performance for supercapacitor and OER applications.

Homogeneous growth of TiO2-based nanotubes on nitrogen-doped reduced graphene oxide and its enhanced performance as a Li-ion battery anode

The pursuit of a promising replacement candidate for graphite as a Li-ion battery anode, which can satisfy both engineering criteria and market needs has been the target of researchers for more than two decades. In this work, we have investigated the synergistic effect of nitrogen-doped reduced graphene oxide (NrGO) and nanotubular TiO₂ to achieve high rate capabilities with high discharge capacities through a simple, one-step and scalable method. First, nanotubes of hydrogen titanate were hydrothermally grown on the surface of NrGO sheets, and then converted to a mixed phase of TiO₂-B and anatase (TB) by thermal annealing. Specific surface area, thermal gravimetric, structural and morphological characterizations were performed on the synthesized product. Electrochemical properties were investigated by cyclic voltammetry and cyclic charge/discharge tests. The prepared anode showed high discharge capacity of 150 mAh g^-1 at 1 C current rate after 50 cycles. The promising capacity of synthesized NrGO-TB was attributed to the unique and novel microstructure of NrGO-TB in which long nanotubes of TiO₂ have been grown on the surface of NrGO sheets. Such architecture synergistically reduces the solid-state diffusion distance of Li⁺ and increases the electronic conductivity of the anode.

Colloidal synthesis of biocompatible iron disulphide nanocrystals

The aim of this research was to synthesis biocompatible iron disulphide nanocrystals at different reaction temperatures using the colloidal synthesis methodology. Synthesis was conducted at the 220-240 °C range of reaction temperatures at intervals of 5 °C in an inert argon atmosphere. The toxicity of iron disulphide nanocrystals was evaluated in vitro using mouse fibroblast cell line. Two complementary assays were conducted: the first to evaluate cell viability of the fibroblast via an MTT assay and the second to determine the preservation of fibroblast nuclei integrity through DAPI staining, which labels nuclear DNA in fluorescence microscopes. Through TEM and HRTEM, we observed a cubic morphology of pyrite iron disulphide nanocrystals ranging in sizes 25-50 nm (225 °C), 50-70 nm (230 °C) and >70 nm (235 °C). Through X-ray diffraction, we observed a mixture of pyrite and pyrrohotite in the samples synthesized at 225 °C and 240 °C, showing the best photocatalytic activity at 80% and 65%, respectively, for the degradation of methylene blue after 120 minutes. In all experimental groups, iron disulphide nanocrystals were biocompatible, i.e. no statistically significant differences were observed between experimental groups as shown in a one-way ANOVA and Tukey's test. Based on all of these results, we recommend non-cytotoxic semiconductor iron sulphide nanocrystals for biomedical applications.

Metastable Marcasite-FeS2 as a New Anode Material for Lithium Ion Batteries: CNFs-Improved Lithiation/Delithiation Reversibility and Li-Storage Properties

Marcasite (m-FeS₂) exhibits higher electronic conductivity than that of pyrite (p-FeS₂) because of its lower semiconducting gap (0.4 vs 0.7 eV). Meanwhile, as demonstrates stronger Fe-S bonds and less S-S interactions, the m-FeS₂ seems to be a better choice for electrode materials compared to p-FeS₂. However, the m-FeS₂ has been seldom studied due to its sophisticated synthetic methods until now. Herein, a hierarchical m-FeS₂ and carbon nanofibers composite (m-FeS₂/CNFs) with grape-cluster structure was designed and successfully prepared by a straightforward hydrothermal method. When evaluated as an electrode material for lithium ion batteries, the m-FeS₂/CNFs exhibited superior lithium storage properties with a high reversible capacity of 1399.5 mAh g^-1 after 100 cycles at 100 mA g^-1 and good rate capability of 782.2 mAh g^-1 up to 10 A g^-1. The Li-storage mechanism for the lithiation/delithiation processes of m-FeS₂/CNFs was systematically investigated by ex situ powder X-ray diffraction patterns and scanning electron microscopy. Interestingly, the hierarchical m-FeS₂ microspheres assembled by small FeS₂ nanoparticles in the m-FeS₂/CNFs composite converted into a mimosa with leaves open shape during Li⁺ insertion process and vice versa. Accordingly, a "CNFs accelerated decrystallization-recrystallization" mechanism was proposed to explain such morphology variations and the decent electrochemical performance of m-FeS₂/CNFs.

Vanadium Nitride Nanowire Supported SnS2 Nanosheets with High Reversible Capacity as Anode Material for Lithium Ion Batteries

The vulnerable restacking problem of tin disulfide (SnS2) usually leads to poor initial reversible capacity and poor cyclic stability, which hinders its practical application as lithium ion battery anode (LIB). In this work, we demonstrated an effective strategy to improve the first reversible capacity and lithium storage properties of SnS2 by growing SnS2 nanosheets on porous flexible vanadium nitride (VN) substrates. When evaluating lithium-storage properties, the three-dimensional (3D) porous VN coated SnS2 nanosheets (denoted as CC-VN@SnS2) yield a high reversible capacity of 75% with high specific capacity of about 819 mAh g(-1) at a current density of 0.65 A g(-1). Remarkable cyclic stability capacity of 791 mAh g(-1) after 100 cycles with excellent capacity retention of 97% was also achieved. Furthermore, discharge capacity as high as 349 mAh g(-1) is still retained after 70 cycles even at a elevated current density of 13 A g(-1). The excellent performance was due to the conductive flexible VN substrate support, which provides short Li-ion and electron pathways, accommodates large volume variation, contributes to the capacity, and provides mechanical stability, which allows the electrode to maintain its structural stability.

Sulfurization of FeOOH nanorods on a carbon cloth and their conversion into Fe2O3/Fe3O4–S core−shell nanorods for lithium storage

This work utilizes a simple approach to significantly enhance the electrochemical performance of iron oxide-based nanomaterials.

Pyrite FeS2–C composite as a high capacity cathode material of rechargeable lithium batteries

A FeS₂–C composite shows improved rate capability but still suffers from fast capacity fading due to either dissolution of lithium polysulfide in ether-based electrolytes or nucleophilic reaction of polysulfide anions in carbonate-based electrolytes.