FeSe Research Articles

Novel Ferrocenyl‐azole Derivatives: Synthesis, DFT Calculation and Unlocking the Anticancer Potential

Herein, a series of novel ferrocenyl/phenyl/thiophenyl‐azoles was disclosed by vinylic amination of ferrocenyl/phenyl/thiophenyl substituted β‐chloro cinnamaldehydes and acrylonitriles. A highly economical and robust chalcogen‐stabilized iron selenide carbonyl cluster Fe3Se2(CO)9 worked as an efficient catalyst under aerobic conditions. The amination of ferrocenyl/phenyl/thiophenyl substituted β‐chloro‐vinylic Csp2‐Cl with azole derivatives was fully established and fabrication of the Csp2‐N bond was completely supported by various spectral analysis. Moreover, wide range of substrates with functionally different azoles were investigated for the present reaction and good to excellent transformation was recorded. Some of the selected ferrocenated azole derivatives were screened for anti‐cancer activity against the prostate cancer cells (PC‐3) and found to be highly active at low concentration of 5.77µM with IC50 value. Furthermore, HOMO and LUMO levels and energy gap of some selected compounds were calculated by the density functional theory (DFT).

Designing a Magnesium/Sodium Hybrid Battery Using Hierarchical Iron Selenide Architecture as Cathode Material and Modified Dual-Ion Salts in Ether as Electrolyte.

We developed a magnesium/sodium (Mg/Na) hybrid battery using a hierarchical disk-whisker FeSe2 architecture (HD-FeSe2) as the cathode material and a modified dual-ion electrolyte. The polarizable Se2- anion reduced the Mg2+ migration barrier, and the 3D configuration possessed a large surface area, which facilitated both Mg2+/Na+ cation diffusion and electron transport. The dual-ion salts with NaTFSI in ether reduced the Mg plating/stripping overvoltage in a symmetric cell. The hybrid battery exhibited an energy density of 260.9 Wh kg-1 and a power density of 600.8 W kg-1 at 0.2 A g-1. It showed a capacity retention of 154 mAh g-1 and a Coulombic efficiency of over 99.5% under 1.0 A g-1 after 800 long cycles. The battery also displayed outstanding temperature tolerance. The findings of 3D architecture as cathode material and hybrid electrolyte provide a pathway to design a highly reliable Mg/Na hybrid battery.

Structural phase transition, s±-wave pairing, and magnetic stripe order in bilayered superconductor La3Ni2O7 under pressure

Motivated by the recently discovered high-Tc superconductor La3Ni2O7, we comprehensively study this system using density functional theory and random phase approximation calculations. At low pressures, the Amam phase is stable, containing the Y2− mode distortion from the Fmmm phase, while the Fmmm phase is unstable. Because of small differences in enthalpy and a considerable Y2− mode amplitude, the two phases may coexist in the range between 10.6 and 14 GPa, beyond which the Fmmm phase dominates. In addition, the magnetic stripe-type spin order with wavevector (π, 0) was stable at the intermediate region. Pairing is induced in the s±-wave channel due to partial nesting between the M = (π, π) centered pockets and portions of the Fermi surface centered at the X = (π, 0) and Y = (0, π) points. This resembles results for iron-based superconductors but has a fundamental difference with iron pnictides and selenides. Moreover, our present efforts also suggest La3Ni2O7 is qualitatively different from infinite-layer nickelates and cuprate superconductors.

Strain Self-Adaptive Iron Selenides Toward Stable Na+ -Ion Batteries with Impressive Initial Coulombic Efficiency.

High tap density electrodes play a vital role in developing rechargeable batteries with high volumetric capacities, however, developing advanced electrodes with satisfied capacity, excellent structural stability, and achieving the resulted batteries with a high initial Coulombic efficiency (ICE) and good rate capability with long lifespan simultaneously, are still an intractable challenge. Herein, an ultrahigh ICE of 94.1% and stable cycling of carbon-free iron selenides anode is enabled with a high tap density of 2.57gcm-3 up to 4000 cycles at 5Ag-1 through strain-modulating by constructing a homologous heterostructure. Systematical characterization and theoretical calculation show that the self-adaptive homologous heterointerface alleviates the stress of the iron selenide anodes during cycling processes and subsequently improves the stability of the assembled batteries. Additionally, the well-formed homologous heterostructure also contributes to the rapid Na+ diffusion kinetic, increased charge transfer, and good reversibility of the transformation reactions, endowing the appealing rate capability of carbon-free iron selenides. The proposed design strategy provides new insight and inspiration to aid in the ongoing quest for advanced electrode materials with high tap densities and excellent stability.

Unveiling intrinsic material and extrinsic pinning dimensionality in superconductors: Why Fe(Se,Te) is able to mimic YBCO

Discovery of iron-based superconductors paved the way to a competitor of high-temperature superconductors, easier to produce, better performing in high fields, and promising to be less expensive. Critical parameters are investigated by resistivity measurements as a function of temperature, field, and angle R(T,H,θ). This work presents a deep analysis of H-θ phase diagram of PLD-processed Fe(Se,Te) superconducting films, thus revealing material and pinning anisotropy at once. By selecting different thresholds along the R(T,H,θ) curves, all possible regimes emerge. Surprisingly, anisotropy arises moving from the upper critical field toward the irreversibility line: gradually a non-monotonous transition from 3D to 2D, and backward to 3D occurs. Although Fe(Se,Te) appears as a 3D superconductor, its anisotropic pinning landscape shows up similarities with an intrinsic layered superconductor and Fe(Se,Te) definitively mimics YBCO. We propose a general method to disentangle, in any other superconductor, material dimensionality and pinning anisotropy that are key constraints for applications.

Copper–Iron Selenides Nanoflakes and Carbon Nanotubes Composites as an Advanced Anode Material for High‐Performance Lithium‐Ion Batteries

Metal selenides are widely considered as an emerging anode electrode material for lithium‐ion batteries (LIBs). Hence, the present study uses a conductive carbon materials matrix such as carbon nanotubes (CNTs) with copper–iron selenide (CuFeSe2). The composites (CuFeSe2@CNTs) are synthesized by a hydrothermal method and examined for electrochemical performance as anode applications in LIBs. Herein, the CuFeSe2@CNTs show excellent specific capacity of 783.7 and 720.6 mA h g−1 at 0.1 and 1 A g−1, respectively. This composite further exhibits a high‐capacity value compared to only FeSe2 and CuFeSe2 and a reversible capacity of 691 mA h g−1 after 200 cycles at 1 A g−1 current density. Moreover, the homogeneous combination of CuFeSe2 nanoflakes and CNTs provides structural stability that reduces the volume change during lithium‐ion interactions and successively improves the conductivity of the complex, which is advantageous for better ion and electron kinetics during the reaction.

Growth mechanism, structure, stoichiometry and optical properties of electrochemically grown iron selenide and ferroselite thin films

In this present work, FeSe and FeSe2 thin films were deposited on ITO substrate at different electrolytic bath temperatures at 30 °C and 70 °C by using electrodeposition method. The growth mechanism was investigated via cyclic voltammetry with the potential window was found to be −1600 to 1600 mV versus SCE and the formation of well adherent film was found to be higher bath temperature. XRD result shows the deposited FeSe and FeSe2 films found to exhibit stoichiometric wurtzite and orthorhombic phases respectively. The microscopic observation shows, the uniform particle growth of FeSe and FeSe2 was found to be higher electrolytic bath temperature at 70 °C. The EDX analysis shows the deposited FeSe and FeSe2 films at higher temperature elemental is stoichiometric ratio. The determined bandgap values for FeSe (1.26 eV) and FeSe2 (1.07 eV) deposited at 70 °C. Also, we observed that the refractive indices (n) values was increased for the film deposited from 30 °C to 70 °C resulting, the estimated refractive indices (n) for FeSe and FeSe2 are 3.16 and 3.45 respectively. Furthermore the most significant optical parameters extinction coefficient (k), optical conductivity (σoptical), real (Ɛ1) and imaginary (Ɛ1) dielectric constants and dissipation factor (tan δ) are determined in order to investigate their usefulness in photovoltaic applications.

Heterostructured FeSe2-CoSe2 Nanorods Supported on Nitrogen and Sulfur co-doped Reduced Graphene Oxide as High‐Performance Electrocatalyst for Oxygen Evolution Reaction

With the aim of hydrogen production from electrochemical water splitting on a high scale, the core challenge is to develop an effective oxygen evolution reaction (OER) electrocatalyst with high activity as well as a low cost. Herein, we developed a heterostructure of Iron and cobalt selenide supported by a dual heteroatom (Nitrogen and Sulphur) doped reduced graphene oxide, synthesized by an easy solvothermal method. The as-synthesized CoSe2-based catalyst consists of urchin-like assembled nanorods resulting in the highly exposed reaction sites and shows excellent electrochemical performance with the much lowest overpotentials of 216 mV and 291 mV at a current density of 10 and 50 mA cm−2, respectively, Tafel slope of 53.4 mV dec−1 and long-term stability for 50 h in an alkaline environment. As a result, the improved OER activity of the as-synthesized electrocatalyst could be attributed to the highly accessible heterointerfaces served as abundant catalytic active sites as well as strong synergistic interaction and enhanced electrical conductivity that increased the movement of electron transfer. The achieved results manifest the superiority of the prepared electrocatalyst towards OER and it can be a remarkable electrocatalyst which is helpful for further development in the practical application of water splitting to decrease energy utilization at a high scale.

Water Splitting Reaction Mechanism on Transition Metal (Fe-Cu) Sulphide and Selenide Clusters-А DFT Study.

The tetracarbonyl complexes of transition metal chalcogenides M2X2(CO)4, where M = Fe, Co, Ni, Cu and X = S, Se, are examined by density functional theory (DFT). The M2X2 core is cyclic with either planar or non-planar geometry. As a sulfide, it is present in natural enzymes and has a selective redox capacity. The reduced forms of the selenide and sulfide complexes are relevant to the hydrogen evolution reaction (HER) and they provide different positions of hydride ligand binding: (i) at a chalcogenide site, (ii) at a particular cation site and (iii) in a midway position forming equal bonds to both cation sites. The full pathway of water decomposition to molecular hydrogen and oxygen is traced by transition state theory. The iron and cobalt complexes, cobalt selenide, in particular, provide lower energy barriers in HER as compared to the nickel and copper complexes. In the oxygen evolution reaction (OER), cobalt and iron selenide tetracarbonyls provide a low energy barrier via OOH* intermediate. All of the intermediate species possess favorable excitation transitions in the visible light spectrum, as evidenced by TD-DFT calculations and they allow photoactivation. In conclusion, cobalt and iron selenide tetracarbonyl complexes emerge as promising photocatalysts in water splitting.

Efficient green hydrogen production through metal–organic framework-derived Ni and Co mediated iron selenide hexagonal nanorods and wireless coupled with photovoltaics for urea and alkaline water electrolysis

Metal-organic framework (MOF)-based catalysts are gaining attention due to their tunable properties. In this study, we synthesized MOF based Ni and Co doped iron selenide (NiCoFeSe) hexagonal nanorods electrocatalyst. This NiCoFeSe catalyst exhibited outstanding performance in the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and urea oxidation reaction (UOR) with impressively low overpotentials of 220, 275 mV for HER, 230, 330 mV for OER, and 210, 300 mV for UOR at current densities of 50 and 100 mAcm−2, respectively. Additionally, we fabricate a wireless flexible and rigid photovoltaic-electrochemical device utilizing NiCoFeSe as both the anode and cathode, achieving an impressive solar-to-hydrogen efficiency of 11.1%. Furthermore, we developed an anion exchange membrane water electrolyzer with NiCoFeSe as anode and cathode, achieving a current density of 1.07 Acm−2 at 1.85 V, along with a cell efficiency of 69.67% and an energy consumption of 47.85 kWh to produce 1 kg of hydrogen.

Controllable hierarchical porous FeSe2 with excellent long cycle lifespan as anode materials for sodium-ion battery

Transition metal selenides are regarded as most promising anode materials for sodium ion battery (SIB) due to their high theoretical specific capacity and environment benignly. Yet the severe volume expansion and sluggish kinetics during cycling leading to capacity fading and material pulverizing restrict its application in SIB. Herein, iron selenides (N–FeSe2) with controlled porous structure is synthesized via facile salt template-assisted method. When N–FeSe2 with hierarchical pore structure serves as anode materials for SIB, a highly reversible capacity of 520.4 mA h g−1 is maintained at 1 A g−1 after 100 cycles. Even at 10 A g−1, the capacity still remains 333 mA h g−1 after 1800 cycles, which shows extraordinary cycle stability. In addition, N–FeSe2 provides excellent diffusion coefficient and high initial Coulomb efficiency (78.9 %), which is attributed to its special hierarchical porous structure and intrinsic pseudocapacitance characteristics. DFT calculations indicate that an increase in vacancy concentration enhances the conductivity of the material, thereby improving its dynamic performance. In this work, a simple and universal synthesis method is developed, and the pore structure and morphology of the final product can be controlled by simple parameter regulation.

Topological magnetic line defects in Fe(Te, Se) high-temperature superconductors

The realization of Majorana zero modes in condensed matter have been attracting enormous interests from fundamental science such as topological quantum computation. Recently iron based superconductors were identified as a high-temperature platform for realizing topological superconductivity and Majorana modes. As unconventional superconductors, one of the most important characteristics of them is that they are in the vicinity of magnetic states due to the strong Hund’s coupling in iron atoms. Here we propose that the line defects with missing Te/Se anions in Fe(Se, Te) superconductors provide the realization of intrinsic antiferromagnetic (AFM) chains with Rashba spin-orbit coupling. Against conventional wisdom, Majorana zero modes (MZMs) can be robustly generated at these AFM chain ends. These results can consistently explain the recent experimental observation of zero-energy end states in line defects of monolayer Fe(Te, Se)/SrTiO3 by scanning tunneling microscopy (STM) measurements. Our research not only demonstrates an unprecedented interplay among native line defect, emergent magnetism and topological superconductivity but also explores a high-temperature platform for Majorana fermions.

Boosting the sodium storage performance of iron selenides by a synergetic effect of vacancy engineering and spatial confinement

Recently, iron selenides have been considered as one of the most promising candidates for the anodes of sodium-ion batteries (SIBs) due to their cost-effectiveness and high theoretical capacity; however, their practical application is limited by poor conductivity, large volume variation and slow reaction kinetics during electrochemical reactions. In this work, spatially dual-carbon-confined VSe-Fe3Se4-xSx/FeSe2-xSx nanohybrids with abundant Se vacancies (VSe-Fe3Se4-xSx/FeSe2-xSx@NSC@rGO) are constructed via anion doping and carbon confinement engineering. The three-dimensional crosslinked carbon network composed of the nitrogen-doped carbon support derived from polyacrylic acid (PAA) and reduced graphene enhances the electronic conductivity, provides abundant channels for ion/electron transfer, ensures the structure integrity, and alleviates the agglomeration, pulverization and volume change of active material during the chemical reactions. Moreover, the introduction of S into iron selenides induces a large number of Se vacancies and regulates the electron density around iron atoms, synergistically improving the conductivity of the material and reducing the Na+ diffusion barrier. Based on the aforementioned features, the as-synthesized VSe-Fe3Se4-xSx/FeSe2-xSx@NSC@rGO electrode possesses excellent electrochemical properties, exhibiting the satisfactory specific capacity of 630.1 mA h g−1 after 160 cycles at 0.5 A/g and the reversible capacity of 319.8 mA h g−1 after 500 cycles at 3 A/g with the low-capacity attenuation of 0.016 % per cycle. This investigation provides a feasible approach to develop high-performance anodes for SIBs via a synergetic strategy of vacancy engineering and carbon confinement.

Three-Dimensional Indium Iron Selenide Nanoarchitecture as an Efficient and Durable Electrocatalyst for the Hydrogen Evolution Reaction

Three-Dimensional Indium Iron Selenide Nanoarchitecture as an Efficient and Durable Electrocatalyst for the Hydrogen Evolution Reaction

The Depairing Current Density of a Fe(Se,Te) Crystal Evaluated in Presence of Demagnetizing Factors

The effect of the demagnetizing factor, regarding the determination of the de-pairing current density Jdep, has been studied in the case of a Fe(Se,Te) crystal, using DC magnetic measurements as a function of a magnetic field (H) at different temperatures (T). First, the lower critical field Hc1(T) values were obtained, and the demagnetization effects acting on them were investigated after calculating the demagnetizing factor. The temperature behaviors of both the original Hc1 values and the ones obtained after considering the demagnetization effects (Hc1demag) were analyzed, and the temperature dependence of the London penetration depth λL(T) was obtained in both cases. In particular, the λL(T) curves were fitted with a power law dependence, indicating the presence of low-energy quasiparticle excitations. Furthermore, by plotting λL−2 as a function of T, we found that our sample behaves as a multigap superconductor, which is similar to other Fe-11 family iron-based compounds. After that, the coherence length ξ values were extracted, starting with the Hc2(T) curve. The knowledge of λL and ξ allowed us to determine the Jdep values and to observe how they are influenced by the demagnetizing factor.

2D Amorphous Iron Selenide Sulfide Nanosheets for Stable and Rapid Sodium-Ion Storage.

Sodium ion batteries (SIBs) suffer from large electrode volume change and sluggish redox kinetics for the relatively large ionic radius of sodium ions, raising a significant challenge to improve their long-term cyclability and rate capacity. Here, it is proposed to apply 2D amorphous iron selenide sulfide nanosheets (a-FeSeS NSs) as an anode material for SIBs and demonstrate that they exhibit remarkable rate capability of 528.7 mAh g-1 at 1 A g-1 and long-life cycle (10000 cycles) performance (300.4 mAh g-1 ). This performance is much more superior to that of the previously reported Fe-based anode materials, which is attributed to their amorphous structure that alleviates volume expansion of electrode, 2D nature that facilitates electrons/ions transfer, and the S/Se double anions that offer more reaction sites and stabilize the amorphous structure. Such a 2D amorphous strategy provides a fertile platform for structural engineering of other electrode materials, making a more secure energy prospect closer to a reality.

Performance improvement of iron chalcogenide films grown at high laser repetition rates by pulsed laser deposition

AbstractFor mass production, a high deposition rate is necessary. A powerful approach is to deposit Fe(Se, Te) (FST) superconducting films at a high laser repetition rate by pulsed laser deposition. Hence, the FST films were grown on flexible metallic tapes using pulsed laser deposition at different laser repetition rates to explore the effect of laser repetition rate on the properties. It was found that as the laser repetition rate increases, the crystallinity and stoichiometry of FST films deteriorate, resulting in a degeneration in superconductivity. The critical temperature of the FST film deposited at a high repetition rate of 120 Hz dropped to 12.89 K. Furthermore, high‐performance FST film was successfully deposited at 120 Hz by increasing the substrate temperature with = 16.96 K and = 18.32 K. The self‐field critical current density can reach 1.3 MA/cm2 at 4.2 K. The analysis of the pinning mechanism reveals that normal surface pinning centers play a dominant part in the FST film and are independent of the temperature. The collective pinning theory states that the FST film exhibits δl pinning. The results may offer valuable information for rapid deposition of FST‐coated conductors for industrial production.

Synthesis and Characterization of Molybdenum- and Sulfur-Doped FeSe.

During the past decade, two-dimensional (2D) layered materials opened novel opportunities for the exploration of exciting new physics and devices owing to their physical and electronic properties. Among 2D materials, iron selenide has attracted much attention from several physicists as they provide a fruitful stage for developing new superconductors. Chemical doping offers a powerful approach to manipulate and optimize the electronic structure and physical properties of materials. Here, to reveal how doping affects the physical properties in FeSe, we report on complementary measurements of molybdenum- and sulfur-doped FeSe with theoretical calculations. Mo0.1Fe0.9Se0.9S0.1 was synthesized by a one-step solid-state reaction method. Crystal structure and morphology were studied using powder X-ray diffraction and scanning electron microscopy. Thermal stability and decomposition behavior in doped samples were studied by thermogravimetric analysis, and to understand the microscopic influence of doping, we performed Raman spectroscopy. First-principles calculations of the electronic structure illustrate distinct changes of electronic structures of the substituted FeSe systems, which can be responsible for their superconducting properties.

Microwave‐Assisted Synthesis of Cobalt‐Based Selenides as Catalyst Precursors for the Alkaline Water Oxidation

When used to promote the oxygen evolution reaction (OER), transition‐metal chalcogenides convert into oxyhydroxide/(hydr)oxide catalysts, the performance of which depends on the properties of the precursor. The present study aims to explore these effects for cobalt and cobalt–iron selenides (CoSe n and Co1Fe1Se n ) prepared using a simple microwave‐assisted method, in comparison to a reference material synthesized by high‐temperature reaction of CoO x H y with Se vapors. Physical characterization of the microwave‐synthesized CoSe n demonstrates their sheet‐like morphology and identifies Co3Se4 as the major phase, which is essentially completely transformed into CoOOH during the OER. The temperature during the microwave‐assisted CoSe n synthesis affects the crystallinity, the electrochemically active surface area, and thereby the performance of the resulting catalysts. Further improvements in the activity are achieved by combining cobalt with iron into a bimetallic Co1Fe1Se n precursor, which transforms in situ into a CoOOH + FeOOH composite and sustains the OER rate of 100 mA cm−2 (33 A g−1) at an overpotential of ≈ 0.31 and 0.26 V at 24 ± 2 and 80 ± 1 °C, respectively. Satisfactory stability of the Co1Fe1Se n ‐derived electrodes is demonstrated through a 4‐day‐long test at 80 ± 1 °C and 100 mA cm−2.

Constructing N, Se co-doped carbon nanofibers encapsulated with hollow FeSe2 nanospheres as electrodes for energy storage

Iron selenide (FeSe2), a p-type narrow band gap (1.0 eV) semiconductor, has been considered as a potential electrode material for electrochemical energy storage owing to its many benefits, including quick electron transfer, excellent electrical conductivity and exceptional theoretical specific capacity. Nevertheless, the volumetric expansion, agglomeration, low ion-diffusion capacity and other inadequacies in the process of discharging and charging. Therefore, FeSe2 is far short of high initial coulomb efficiency, long-cycle stability, and excellent rate performance. The greatest obstacle to the practical use of energy storage systems is these drawbacks. Herein, the electrospinning and a thermally-induced selenization route are adopted to encapsulate the FeSe2 hollow nanospheres into the intertwined Se, N co-doped carbon nanofibers (Se, N-FeSe2CNFs). Density functional theory calculation delivers that Se, N-FeSe2CNFs nanocomposite presents extremely low bandgap and high density of states at the Femi level, demonstrating significantly increased conductivity. When assembling into the all-solid-state symmetric supercapacitors (ASSSCs), the Se, N-FeSe2CNFs ASSSCs provide a remarkable specific capacity of 330.2 F g−1 and maintain 92.0% after 5000 cycles at 2 A g−1. Meanwhile, the resistance of charge transfer decreases from 0.73 Ω (FeSe2) to 0.28 Ω (Se, N-FeSe2CNFs). Moreover, the Se, N-FeSe2CNFs ASSSCs deliver 128.6 Wh kg−1 (energy density) at about 800 W kg−1 (power density). Additionally, the Se, N-FeSe2CNFs anodes also have outstanding reversible capacity (549.5 mAh g−1 at 0.1 A g−1) and stability of long-circulation (481.3 mAh g−1 after 100 circles and 480.9 mAh g−1 after 200 circles at 0.1 A g−1) for sodium-ion batteries (SIBs). The superb property of energy storage can be due to the encapsulated structure that can maintain the integrity of structures for electrodes during electrochemical reactions and the Se, N heteroatoms doped CNFs that can conducive to ions/charges transport and storage. The designed encapsulated structure and synthesis approach have broad application prospects in electrochemical energy storage.