FeS2 Nanoparticles Research Articles

In situ observations of thermally induced phase transformations in iron sulfide nanoparticles

Iron pyrite (FeS2) exhibits dynamic thermal stability and represents an ideal model system to probe complex phase transformations in materials. At elevated temperatures, the sublimation of S atoms from the FeS2 lattice results in a phase transformation to one of the many polymorphic forms of pyrrhotite, i.e., from Fe1-XS (where 0 ≤ X < 0.2) to stoichiometric FeS. The complex nature of this phase transformation remains relatively unexplored at the nanoscale. Here, we use in situ transmission electron microscopy (TEM) and in situ X-ray diffraction (XRD) to observe the phase transformation of ~150 nm pyrite nanoparticles to pyrrhotite in vacuum. Although the overall shape of the nanoparticles remains cubic, the crystal structure of the nanoparticles changes from cubic pyrite to hexagonal pyrrhotite at ~400–450oC, which is ~100–150oC lower than reported values of bulk pyrite. Interestingly, our in situ observations do not evidence a core-shell transformation model which has been reported for the phase transformation of bulk pyrite to pyrrhotite, indicating the role of shorter length scales for diffusion in nanoparticles, as well as the role of S vacancies that facilitate faster atomic diffusion and rearrangements. In addition, the heating ramp rate was found to influence the phase transition temperature with lower temperatures of transformation seen for higher heating rates indicating the role of kinetic effects on phase transformation. We expect our detailed insights will help advance the use of FeS2 nanoparticles in high-temperature applications including catalysis and high-temperature batteries.

A Highly Stable Metal-Organic Framework-Engineered FeS2/C Nanocatalyst for Heterogeneous Electro-Fenton Treatment: Validation in Wastewater at Mild pH.

Herein, the novel application of FeS2/C nanocomposite as a highly active, stable, and recyclable catalyst for heterogeneous electro-Fenton (EF) treatment of organic water pollutants is discussed. The simultaneous carbonization and sulfidation of an iron-based metal-organic framework (MOF) yielded well-dispersed pyrite FeS2 nanoparticles of ∼100 nm diameter linked to porous carbon. XPS analysis revealed the presence of doping N atoms. EF treatment with an IrO2/air-diffusion cell ensured the complete removal of the antidepressant fluoxetine spiked into urban wastewater at near-neutral pH after 60 min at 50 mA with 0.4 g L-1 catalyst as optimum dose. The clear enhancement of catalytic activity and stability of the material as compared to natural pyrite was evidenced, as deduced from its characterization before and after use. The final solutions contained <1.5 mg L-1 dissolved iron and became progressively acidified. Fluorescence excitation-emission spectroscopy with parallel factor analysis demonstrated the large mineralization of all wastewater components at 6 h, which was accompanied by a substantial decrease of toxicity. A mechanism with •OH as the dominant oxidant was proposed: FeS2 core-shell nanoparticles served as Fe2+ shuttles for homogeneous Fenton's reaction and provided active sites for the heterogeneous Fenton process, whereas nanoporous carbon allowed minimizing the mass transport limitations.

FeSe2/nitrogen-doped carbon as anode material for Potassium-ion batteries

Abstract Potassium-ion batteries (PIBs) have aroused intensive interests as a promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage, however, the lack of high performance anode material is one of the key challenges for their development, which is mainly caused by the large size of potassium ions inducing severe volume change and pulverization of anode materials. Here, we report a FeSe2/nitrogen-doped carbon (FeSe2/NC) composite with a structure of N-doped carbon-coated FeSe2 nanoparticles anchored on thin carbon nanosheets matrix as an anode material for PIBs. Benefiting from the nanosized particles reducing the ion diffusion length, the protective carbon coating alleviating volume fluctuation, and the carbon nanosheets matrix facilitating electrons transport, the FeSe2/NC electrode delivers high capacities of 434 mA h g−1 after 70 cycles at 0.1 A g−1, and 301 mA h g−1 after 250 cycles at 1.0 A g−1. Meanwhile, the potassium storage mechanism of FeSe2 has been preliminarily investigated by using ex situ X-ray diffraction technique and high-resolution transmission electron microscopy. The remarkable performance and easy preparation demonstrate the great promise of FeSe2/NC composite as a potential anode material for PIBs.

Novel self-supported MoS2/FeS2 nanocomposite as an excellent electrocatalyst for hydrogen evolution

The development of earth-abundant electrocatalysts to replace high-cost precious metal Pt for water splitting to generate H2 is a hot topic in the researches on clean energy. Among them, MoS2 nanostructures have intrigued great interest for its low cost and potential high performance. However, due to the intrinsically low conductivity, its H2 evolution activity is not satisfactory as an applicable electrocatalyst. Herein we report a novel MoS2/FeS2 nanocomposite grown directly on carbon cloth by a facile method based on simple one-step chemical vapor deposition, which has significantly improved H2 evolution performance compared to its pure MoS2 nanosheets counterpart. Such self-supported MoS2/FeS2 nanocomposite electrode exhibits a relatively low overpotential of 134 mV at a current of 10 mA cm−2, a quite small Tafel slope of 76.8 mV⋅dec−1 and excellent electrocatalytic durability in 0.5 mol L−1 H2SO4. The remarkably high H2 evolution activity could be ascribed to the fully exposed and increased number of active sites, enhanced charge transfer rate between MoS2 nanosheets and FeS2 nanoparticles in the composite, and the 3D self-supported structure. This strategy to prepare MoS2/FeS2 nanocomposite with controllable morphology and highly active microstructure would provide a new way for the improvement of the electrocatalytic H2 evolution activity and durability of MoS2.

Rational design of hierarchical FeSe2 encapsulated with bifunctional carbon cuboids as an advanced anode for sodium-ion batteries.

Earth-abundant transition-metal selenides (TMSs) have aroused great interest towards their application in sodium-ion batteries (SIBs). Herein, we present Fe-based Prussian blue analogs (PBA) modified by graphene oxide as precursors to synthesize FeSe2 nanoparticles within a nitrogen-doped carbon (NC) matrix and graphene layer (FeSe2/NC@G). The bifunctional carbon wrapped FeSe2/NC@G shows excellent sodium-storage performance with a large reversible capacity of 331 mA h g-1 at 5.0 A g-1 and a high cyclability of 323 mA h g-1 at the current density of 2.0 A g-1 after 1000 cycles (82% capacity retention). Furthermore, full SIBs are also fabricated and exhibit superior capacities and stabilities. The remarkable electrochemical properties result from the formation of an Fe-O-C chemical bond in the composite with enhanced electronic/ionic diffusion kinetics and structural integrity. This study paves the way for the successful synthesis of novel nanostructural TMSs which can be utilized in energy storage system application.

Study of Structural and Optical Properties of FeS2 Nanoparticles Prepared by Polyol Method

Study of Structural and Optical Properties of FeS2 Nanoparticles Prepared by Polyol Method

High peroxidase-like activity realized by facile synthesis of FeS2 nanoparticles for sensitive colorimetric detection of H2O2 and glutathione

In the last decades, enzyme mimics have been regarded as strong substitutes to natural enzymes. The construction of biosensors based on these enzyme mimics with competitive catalytic activity and substrate specificity has attracted a lot of research interest. Herein, for the first time, we investigated the capability of nanoscale FeS2 to serve as enzyme mimics. Then, a facile and effective biosensor is fabricated based on its intrinsic peroxidase-like catalytic activity. In the presence of H2O2, FeS2 nanoparticles (NPs) possess high peroxidase-like activity to 3,3′,5,5′-tetramethylbenzidine (TMB) oxidation, which can be ascribed to the generation of hydroxyl radicals (·OH) from the H2O2 decomposition catalyzed by FeS2 NPs. As for TMB, the resulting Michaelis−Menten constant (Km) value of FeS2 NPs is found to be about 12 times lower than that of natural horseradish peroxidase (HRP), highlighting the superiority of FeS2 NPs. Based on these intriguing observations, a reliable colorimetric method is then developed for detection of H2O2 and glutathione (GSH) by a simple mix-and-detect strategy. The detection limits of H2O2 and GSH are as low as 0.91 μM and 0.15 μM (3σ/slope), respectively. Moreover, FeS2 NPs can also catalyse the photoluminescence (PL) substrate terephthalic acid (TA) under the assistance of H2O2. This work remarkably extends the utilization of FeS2 NPs in the construction of colorimetric and PL biosensors in the fields of biosensing, environmental monitoring, and medical diagnosis.

Ultrafine Cobalt‐Doped Iron Disulfide Nanoparticles in Ordered Mesoporous Carbon for Efficient Hydrogen Evolution

AbstractDesigning earth‐abundant and efficient electrocatalysts to replace noble metals is highly desired for the hydrogen evolution reaction (HER) in water electrolysis. In this study, we constructed a self‐supported electrode with ordered mesoporous carbon film coated carbon fibers as a substrate and Co doped FeS2 nanoparticles as catalytically active phase for the HER. The ordered mesoporous carbon served as nanoreactor to restrict the growth of sulfide particles and prevent them from agglomeration, leading to the formation of ultrafine and highly dispersed sulfide of ∼5 nm, which enables the exposure of abundant active sites. Meanwhile, the Co atom doping enhanced the adsorption of the catalyst towards hydrogen, thereby improving its intrinsic activity. As a result, the electrode exhibited outstanding catalytic activity for the HER in acid electrolyte, manifesting a current density of 10 mA cm−2 at an overpotential of 92 mV and a small Tafel slope of 59 mV dec−1.

High loading FeS2 nanoparticles anchored on biomass-derived carbon tube as low cost and long cycle anode for sodium-ion batteries

In recent years, the sodium storage mechanism and performance optimization of FeS2 have been studied intensively. However, before the commercial application of FeS2, preconditions of low-cost, simple craft and scale production of nanoscale FeS2 are also essential. Based on above challenges, mesh-like FeS2/carbon tube/FeS2 composites are prepared simply from green, low-cost and renewable natural herb in this work. With the assistance of protogenetic interconnected carbon tube network (only 5.3 wt%), FeS2/carbon tube/FeS2 composites show high capacity (542.2 mA h g−1), good stability (< 0.005% per cycle over 1000 cycles), and excellent rate performance (426.2 mA h g−1 at 2 A g−1). The outstanding electrochemical performance of FeS2/carbon tube/FeS2 composites may be attributed to the unique interconnected reticular structure, meaning that FeS2 nanoparticles are effectively immobilized by carbon tube network via physical encapsulation and chemical bonding. More importantly, this work may provide green and low cost preparation method for specially structured metal sulfides/carbon composites, which promotes their commercial utilization in environmentally friendly energy storage system.

Hydrogenation of Functionalized Nitroarenes Catalyzed by Single‐Phase Pyrite FeS2 Nanoparticles on N,S‐Codoped Porous Carbon

AbstractInvited for this month′s cover is the group of Yong Yang at the Qingdao Institute of Bioenergy and Bioprocess Technology. The image shows single‐phase pyrite FeS2 nanoparticles with uniform size supported on N,S‐codoped porous carbon, which allows for highly active and chemoselective hydrogenation of functionalized nitroarenes bearing readily reducible groups to their corresponding anilines in water. The Full Paper itself is available at 10.1002/cssc.201901867.

Hydrogenation of Functionalized Nitroarenes Catalyzed by Single-Phase Pyrite FeS2 Nanoparticles on N,S-Codoped Porous Carbon.

Catalytic hydrogenation of nitroarenes is an industrially very important and environmentally friendly process for the production of anilines; however, highly chemoselective reduction of nitroarenes decorated with one or more reducible groups in a nitroarene molecule remains a challenge. Herein, a novel hybrid non-noble iron-based nanocatalyst (named as FeS2 /NSC) was developed, which was prepared from biomass as C and N source together with inexpensive Fe(NO3 )3 as Fe source through high-temperature pyrolysis in a straightforward and cost-effective procedure. Comprehensive characterization revealed that single-phase pyrite FeS2 nanoparticles with precisely defined composition and uniform size were homogeneously dispersed on N,S-codoped porous carbon with large specific surface area, hierarchical porous channels, and high pore volume. The resultant catalyst FeS2 /NSC demonstrated good catalytic activity for hydrogenation of functionalized nitroarenes with good tolerance of various functional groups in water as a sustainable and green solvent. Compared with bulk pyrite FeS2 and other non-noble metal-based heterogeneous catalysts reported in the literature, a remarkably enhanced activity was observed under mild reaction conditions. More importantly, FeS2 /NSC displayed exclusive chemoselectivity for the reduction of nitro groups for nitroarenes bearing varying readily reducible groups.

Simple preparation and excellent microwave attenuation property of Fe3O4- and FeS2- decorated graphene nanosheets by liquid-phase exfoliation

Graphene nanosheets (GNS) were fabricated by the liquid phase exfoliation technique. The Fe3O4, FeS2 nanoparticles and Fe3O4@GNS, FeS2@GNS nanohybrids were prepared as the microwave absorber. Morphology investigation by means of SEM and TEM shown that GNS were decorated uniformly by the nanoparticles. The microwave absorption properties of Fe3O4@GNS and FeS2@GNS nanohybrids with different GNS contents were measured in the frequency range of 2–18 GHz. Compared with the Fe3O4@GNS nanohybrids, FeS2@50%GNS nanohybrids possessed enhanced microwave attenuation ability. The minimum reflection loss (RL) was −38.2 dB at 12.2 GHz and the effective absorption bandwidth (RL ≤ −10 dB) was 3.09 GHz, corresponding to the thickness of 1.7 mm. This study presented a feasible and cost reduction method to design FeS2 and FeS2@GNS nanohybrids as the promising microwave absorber.

FeS2 nanoparticles embedded in N/S co-doped porous carbon fibers as anode for sodium-ion batteries

FeS2 is a promising electrode material for sodium ion batteries (SIBs) because of its high theoretical capacity, rich reserves, and eco-friendly nature. In this study, N and S doped (N, S-co-doped) carbon fibers (CFs) encapsulated FeS2 nanoparticles (5–12 nm) and adherent FeS2 nanoflakes (denoted as FeS2@CF-NS), were synthesized by electrostatic spinning and subsequent thermal treatment. In this structure, the FeS2 nanoparticles and the FeS2 nanoflakes shorten the Na+ diffusion distance; the N, S co-doping and defect-rich sites in the carbon fibers accelerate the Na+/e− transmission and buffer the volume expansion during the Na-FeS2 conversion reaction. These merits synergistically contribute to the notable sodium storage performance of FeS2@CF-NS. As anode for Na-ion half batteries, the FeS2@CF-NS exhibits high capacity (637.1 mAh/g at 1 A/g after 400 cycles) and excellent rate capacity (431.1 mAh/g at 5 A/g). Kinetic analysis confirms that this composite structure stimulates the pseudocapacitance Na+ storage mechanism and enables a capacitive contribution ratio as high as 92.7% with respect to the total capacity. In combination with Na3V2(PO4)3-C cathode, the FeS2@CF-NS also achieves remarkably high specific capacity (561.1 mAh/g at 1 A/g after 500 cycles) and stable cyclability (338.6 mAh/g at 5 A/g after 5000 cycles) in full cells.

Controllable Synthesis of Iron Sulfide/CNT Nanocomposites in Solvothermal System

AbstractIron sulfide (FeS2 and Fe7S8) has been considered as one of the promising electrode materials in the field of solar cell and lithium ion battery owing to their unique properties. Herein a facile solvothermal method is reported for preparing iron sulfide/carbon nanotube (CNT) nanocomposites with desired structure and composition. FeS2 nanoparticles can be successfully loaded on the surface of CNT, and the FeS2 nanoparticles uniformly distribute along the CNT. With the assistance of polyvinylpyrrolidinone (PVP), flower‐like Fe7S8@CNT precursor and flower‐like Fe7S8 precursor can be obtained, respectively. When the flower‐like precursors are annealed in the tube furnace with Ar atmosphere, the diameter of the samples decrease from micron level (≈1 µm) to submicron‐level (200–400 nm).

Origin of Ferromagnetism in Pure and Ion Doped Pyrite FeS2 Nanoparticles

It is demonstrated theoretically that the magnetization of FeS2 nanoparticles is originated by the appearance of sulfur vacancies at the surface, where FeS2 undergoes a reduction to FeS. This change is accompanied by a transition from the zero spin configuration of Fe2+ ions to a spin S = 2 state. Additionally there are uncompensated Fe spins on the surface. As result one observes ferromagnetism which is described using the Heisenberg model. The applied Green's function method allows calculating the magnetization of FeS2 nanoparticles versus the FeS concentration on the surface at finite temperature and for different particles sizes as well as the increase of the magnetization of FeS2 nanoparticles with decreasing particle size. It is shown that Co ion doping can induce ferromagnetism in bulk FeS2 and enhance it in FeS2 nanoparticles.

Mechanochemically synthesized pyrite and its electrochemical behavior as cathode for lithium batteries

This study presents a simple and scalable synthesis of pyrite (FeS2) starting from S and Fe powders, which involves high-energy ball milling of precursor powders followed by a thermal treatment. The formation of the desired product was confirmed by X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. After the synthesis, spherical FeS2 nanoparticles of ~ 85 nm in size were obtained, with a highly crystalline face-centered cubic structure and no secondary phases. The synthesized material was tested as cathode material for lithium batteries. The cathodes delivered good electrochemical lithium storage properties, such as a reversible capacity as high as 470 mAh g−1 even after 120 cycles and a good rate capability. Furthermore, aspects regarding the reaction mechanism and common electrochemical features of Li/FeS2 batteries are discussed.

Poly‐3‐hexylthiophene doped with iron disulfide nanoparticles for hybrid solar cells

In this work, the pyrite crystalline phase of iron disulfide nanoparticles (FeS2) about 20 to 30 nm was obtained by a two-pot thermal method at 220°C. Subsequently, different concentrations of these nanoparticles were used as a doping agent for the conjugated poly-3-hexylthiophene (P3HT). The electrical resistivity of P3HT was decreased almost three orders of magnitude while adding FeS2 nanoparticles as doping, and dichlorobenzene solvent was a determinant factor for the dispersion of polymer with nanoparticles. Doped-P3HT dichlorobenzene solution was spin coated onto the FTO/TiO2 substrate to fabricate the FTO/TiO2/P3HT:FeS2/C-Au hybrid solar cells. Moreover, the power conversion efficiency (PCE) of hybrid devices was studied as a function of pyrite FeS2 nanoparticle concentration. The highest efficiency of 0.83% was obtained at 1% concentration of FeS2 nanoparticles. Hence, the results revealed that the FeS2 nanoparticles could be considered as an alternative charge carrier to develop the bulk hybrid solar cells.

Rational synthesis of two-dimensional G@porous FeS2@C composite as high-rate anode materials for sodium/potassium ion batteries

Pyrite (FeS2) with the advantages of high capacity, low cost and environmental benign has been considered as a promising anode material for alkali metal (Li, Na, K) ion batteries. However, the large volume expansion and its semiconductor nature result in poor battery performance and hamper its practical applications. To overcome these drawbacks, we rationally construct a two-dimensional FeS2-carbon architecture, from which porous FeS2 nanoparticles are distributed within reduced graphene oxide matrix and carbon coating shell with abundant interior void space. Benefiting from its structure properties with conductive carbon network, protective carbon layer, and interior void room, as-prepared rGO@p-FeS2@C composite displays superior electrochemical performance as anode materials for sodium/potassium ion batteries. For sodium storage, it exhibits good cyclic performance with a high capacity 598 mA h g−1 sustained after 100 cycles at 0.1 A g−1, and excellent rate capability (428 mA h g−1 at 10 A g−1). For potassium storage, it also maintains a superior rate capacity of 298 mA h g−1 at 2 A g−1. Moreover, pseudocapacity has been proved to be dominated in charge/discharge process, accounting for the excellent rate performance.

Graphene-Encapsulated FeS2 in Carbon Fibers as High Reversible Anodes for Na+ /K+ Batteries in a Wide Temperature Range.

Developing low cost, long life, and high capacity rechargeable batteries is a critical factor towards developing next-generation energy storage devices for practical applications. Therefore, a simple method to prepare graphene-coated FeS2 embedded in carbon nanofibers is employed; the double protection from graphene coating and carbon fibers ensures high reversibility of FeS2 during sodiation/desodiation and improved conductivity, resulting in high rate capacity and long-term life for Na+ (305.5 mAh g-1 at 3 A g-1 after 2450 cycles) and K+ (120 mAh g-1 at 1 A g-1 after 680 cycles) storage at room temperature. Benefitting from the enhanced conductivity and protection on graphene-encapsulated FeS2 nanoparticles, the composites exhibit excellent electrochemical performance under low temperature (0 and -20 °C), and temperature tolerance with stable capacity as sodium-ion half-cells. The Na-ion full-cells based on the above composites and Na3 V2 (PO4 )3 can afford reversible capacity of 95 mAh g-1 at room temperature. Furthermore, the full-cells deliver promising discharge capacity (50 mAh g-1 at 0 °C, 43 mAh g-1 at -20 °C) and high energy density at low temperatures. Density functional theory calculations imply that graphene coating can effectively decrease the Na+ diffusion barrier between FeS2 and graphene heterointerface and promote the reversibility of Na+ storage in FeS2 , resulting in advanced Na+ storage properties.

Sulfidation of Magnetite Nanoparticles – Following the Polysulfide Pathway

The in‐situ sulfidation of sub‐10 nm sized Fe3O4 and partial‐substituted CoxFe3–xO4 (x = 0.25–0.75) nanoparticles by hot‐injection of sulfur dissolved in oleylamine (OA) is strongly time‐ and temperature dependent. Fe3O4 nanoparticles are completely converted within 5 minutes into Fe3S4 nanoparticles with preservation of the spinel structure at 250 °C, whereas higher reaction temperatures and prolonged reaction times result in additional sulfur uptake and formation of pyrite FeS2 nanoparticles. The formation of the cubic (Co,Fe)S2 phase was observed in sulfidation reactions of CoxFe3–xO4, even with low Co substitution levels (x = 0.25). The chemical composition, morphology, and phase purity of the resulting nanoparticles were investigated by EDX, XRD, TEM, and XPS.