Fe Atoms Research Articles

Magneto-Optic and thermoelectric response of doped SrZrO3 for energy storage applications

Using first-principles calculations, we have investigated the electronic, optical, magnetic and thermoelectric properties of the pristine and doped SrZrO3 (SZO) with Mn, Co, and Fe atoms at Sr-site. Our calculations shows that the Mn. Co, and Fe atoms at Sr-site can be easily incorporated in SZO due to their lower formation energies. The pristine SZO exhibit a non-magnetic semiconductor nature with a band gap of 4.06 eV. Interestingly, the dopants Mn, Co, and Fe atoms alters the semiconductor nature of SZO to magnetic one with a band gap values of 1.38(↑)/1.74(↓), 2.98(↑)/0.0(↓), and 0.0(↑)/1.87(↓) for Mn-, Co–, and Fe-doped SZO. This 100 % spin-polarization near the fermi-level, confirming the half-metallic nature of the X-SZO (X = Mn, Co, Fe). Importantly, the magnetic anisotropy energy (MAE) of 1.27 meV, 1.45 meV, and 0.67 meV is estimated for Mn-, Co–, and Fe-doped SZO, respectively. Thus, the realization of MAE could pave a way to utilize Mn-, Co–, and Fe-doped SZO for applications in magnetic semiconductor devices. Optical absorption of Mn-SZO spectra exhibits blueshift upon introducing impurities and materials exhibits good absorption in the visible region. A drop in reflectivity and rise in conductivity in the high energy Ultraviolet region make these materials as potential candidate for fabrication of devices in the field of photodetectors, optoelectronic, power electronics, solar cells, photonic and photovoltaics. The ZT value is recorded 0.35, 0.45, 1.12 and 0.55 for pristine, Mn-SrZrO3, Co-SZO and Fe-SZO respectively at different temperature values. It would be ideal to perform more experimental research on the effective application of these systems in the domains of magnetic semiconductor devices and photo-electronics.

Atomic-scale magnetic doping of monolayer stanene by revealing Kondo effect from self-assembled Fe spin entities

Atomic-scale spin entity in a two-dimensional topological insulator lays the foundation to manufacture magnetic topological materials with single atomic thickness. Here, we have successfully fabricated Fe monomer, dimer and trimer doped in the monolayer stanene/Cu(111) through a low-temperature growth and systematically investigated Kondo effect by combining scanning tunneling microscopy/spectroscopy (STM/STS) with density functional theory (DFT) and numerical renormalization group (NRG) method. Given high spatial and energy resolution, tunneling conductance (dI/dU) spectra have resolved zero-bias Kondo resonance and resultant magnetic-field-dependent Zeeman splitting, yielding an effective spin Seff = 3/2 with an easy-plane magnetic anisotropy on the self-assembled Fe atomic dopants. Reduced Kondo temperature along with attenuated Kondo intensity from Fe monomer to trimer have been further identified as a manifestation of Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction between Sn-separated Fe atoms. Such magnetic Fe atom assembly in turn constitutes important cornerstones for tailoring topological band structures and developing magnetic phase transition in the single-atom-layer stanene.

Effect of Y element on atomic structure, glass forming ability and magnetic properties of FeBC alloy

Abstract The atomic structure of amorphous alloys plays a crucial role in determining both their glassforming ability and magnetic properties. In this study, we investigate the influence of adding the Y element on the glass-forming ability and magnetic properties of Fe86-xYxB7C7 (x=0, 5, 10 at.%) amorphous alloys via both experiments and ab initio molecular dynamics simulations. Furthermore, we explore the correlation between local atomic structures and properties. Our results demonstrate that an increased Y content in the alloys leads to a higher proportion of icosahedral clusters, which can potentially enhance both glass-forming ability and thermal stability. These findings have been experimentally validated. The analysis of the electron energy density and magnetic moment of the alloy reveals that the addition of Y leads to hybridization between Y-4d and Fe-3d orbitals, resulting in a reduction in ferromagnetic coupling between Fe atoms. This subsequently reduces the magnetic moment of Fe atoms as well as the total magnetic moment of the system, which is consistent with experimental results. The results could help understand the relationship between atomic structure and magnetic property, and providing valuable insights for enhancing the performance of metallic glasses in industrial applications.

Competitive segregation to grain boundaries between Cr and Co in FeNiCrCo alloy

Alloying elements segregating to grain boundaries (GBs) is vital in determining structural stability and mechanical properties of alloys, especially in high‐entropy alloys (HEAs) that consist of multiple elements. However, some details remain unclear, such as the process of varied atoms (Cr and Co) cosegregation to GBs in FeNiCrCo alloy. Therefore, the competition and cooperation between Fe, Ni, Cr, and Co atoms segregating to GBs of FeNiCrCo alloy were investigated via molecular dynamic (MD) simulation. Five [110] symmetric tilt GBs of FeNiCrCo were applied to study the relation between the tendency of atomic segregation especially Cr and Co and GB characters including GB energy and GB excess free volume (GB excess volume). A competitive segregation phenomenon between Cr and Co atoms was discovered, which could be dominated by GB excess volume and different atomic radii among components.

Spin modulation of single Fe atoms with thiolate‐poisoned Pd nanoclusters for highly efficient ammonia synthesis

AbstractNitrate reduction toward ammonia is pivotal in energy and environmental domains but faces challenges in achieving simultaneous high selectivity and activity. Manipulating interactions between intermediates and metal species is deemed effective for catalytic enhancement. In this study, a uniformly configured Fe1‐N4 single‐atom catalyst with four‐coordination was synthesized. Subsequent deposition of thiol‐poisoned Pd nanoclusters provided a platform to investigate the neighboring effect of Pd nanoclusters, excluding activity influences from Pd catalysts. Through this neighbor engineering, the Fe 3d electron spin configuration shifted from low spin to medium spin (MS). Experimental and theoretical analyses affirmed that MS Fe species optimized nitrate reduction by enhancing the *NO desorption process. This spin‐modulated Fe single‐atom catalyst demonstrated superior activity (392.16 mmol−1 gcat−1 h−1, ~40 mol−1 gFe−1 h−1) and a Faraday efficiency of 98.6% at −0.5 V vs. RHE, surpassing reported values. This study presents a promising strategy for nitrogen‐chemistry transition metal catalysts.

Effect of Ce on Inclusions and Precipitates in 10Cr5MoV Steel and the Microscopic Behavior of Solid Solution Ce in Steel

In this article, the effects of Ce (0–120 ppm) on inclusions and precipitates in industrially produced CO2/H2S‐resistant 10Cr5MoVCe special oil well pipe steel and the microscopic behavior of Ce solid solution in steel were systematically studied by scanning electron microscopy, transmission electron microscopy, electrolysis separation of nonaqueous mixed solutions, and first‐principles calculations. After adding Ce to 10Cr5MoV steel the inclusions changed from chain‐like Al2O3 inclusions to polygonal Ce–O–S–Al–Ca complex inclusions and spheroidal Ce2O3, CeAlO3, Ce2O2S, and CeS inclusions. When the total Ce content was 25–120 ppm, the solid solution Ce content was maintained at about 20% of the total Ce content. The Ce had no significant influences on the types of chromium carbide precipitates, and the chromium carbide precipitates of all tested steels were Cr23C7 and Cr7C3. However, with the increase of Ce, the content of Cr23C7 and Cr7C3 precipitates decreased slightly, from 1.27% without Ce to 1.18% when Ce was 120 ppm. The first‐principles calculation results show that there was strong interaction between Fe, Ce, and Cr. Ce enhanced the interaction force between the Fe and Cr atoms, and improved the stability of the system, which facilitated the solid solution of Cr in the Fe–Cr system.

Loading of Single Atoms of Iron, Cobalt, or Nickel to Enhance the Electrocatalytic Hydrogen Evolution Reaction of Two-Dimensional Titanium Carbide.

The rational design of advanced electrocatalysts at the molecular or atomic level is important for improving the performance of hydrogen evolution reactions (HERs) and replacing precious metal catalysts. In this study, we describe the fabrication of electrocatalysts based on Fe, Co, or Ni single atoms supported on titanium carbide (TiC) using the molten salt method, i.e., TiC-FeSA, TiC-CoSA, or TiC-NiSA, to enhance HER performance. The introduction of uniformly distributed transition-metal single atoms successfully reduces the overpotential of HERs. Overpotentials of TiC-FeSA at 10 mA cm-2 are 123.4 mV with 61.1 mV dec-1 Tafel slope under acidic conditions and 184.2 mV with 85.1 mV dec-1 Tafel slope under alkaline conditions, which are superior to TiC-NiSA and TiC-CoSA. TiC samples loaded with transition-metal single atoms exhibit high catalytic activity and long stability under acidic and basic conditions. Density functional theory calculations indicate that the introduction of transition-metal single atoms effectively reduces the HER barrier of TiC-based electrocatalysts.

Multi-Omics Study on Molecular Mechanisms of Single-Atom Fe-Doped Two-Dimensional Conjugated Phthalocyanine Framework for Photocatalytic Antibacterial Performance.

Currently, photocatalysis of the two-dimensional (2D) conjugated phthalocyanine framework with a single Fe atom (CPF-Fe) has shown efficient photocatalytic activities for the removal of harmful effluents and antibacterial activity. Their photocatalytic mechanisms are dependent on the redox reaction-which is led by the active species generated from the photocatalytic process. Nevertheless, the molecular mechanism of CPF-Fe antimicrobial activity has not been sufficiently explored. In this study, we successfully synthesized CPF-Fe with great broad-spectrum antibacterial properties under visible light and used it as an antibacterial agent. The molecular mechanism of CPF-Fe against Escherichia coli and Salmonella enteritidis was explored through multi-omics analyses (transcriptomics and metabolomics correlation analyses). The results showed that CPF-Fe not only led to the oxidative stress of bacteria by generating large amounts of h+ and ROS but also caused failure in the synthesis of bacterial cell wall components as well as an osmotic pressure imbalance by disrupting glycolysis, oxidative phosphorylation, and TCA cycle pathways. More surprisingly, CPF-Fe could disrupt the metabolism of amino acids and nucleic acids, as well as inhibit their energy metabolism, resulting in the death of bacterial cells. The research further revealed the antibacterial mechanism of CPF-Fe from a molecular perspective, providing a theoretical basis for the application of CPF-Fe photocatalytic antibacterial nanomaterials.

Photo‐promoted rapid reconstruction induced alterations in active site of Ag@amorphous NiFe hydroxides for enhanced oxygen evolution reaction

AbstractThe dynamic surface self‐reconstruction behavior in local structure correlates with oxygen evolution reaction (OER) performance, which has become an effective strategy for constructing the catalytic active phase. However, it remains a challenge to understand the mechanisms of reconstruction and to accomplish it fast and deeply. Here, we reported a photo‐promoted rapid reconstruction (PRR) process on Ag nanoparticle‐loaded amorphous Ni‐Fe hydroxide nanosheets on carbon cloth for enhanced OER. The photogenerated holes generated by Ag in conjunction with the anodic potential contributed to a thorough reconstruction of the amorphous substrate. The valence state of unsaturated coordinated Fe atoms, which serve as active sites, is significantly increased, while the corresponding crystalline substrate shows little change. The different structural evolutions of amorphous and crystalline substrates during reconstruction lead to diverse pathways of OER. This PRR utilizing loaded noble metal nanoparticles can accelerate the generation of active species in the substrate and increase the electrical conductivity, which provides a new inspiration to develop efficient catalysts via reconstruction strategies.

Simulation of cavitation erosion damage and structural evolution caused by nano-bubbles for iron

In this work, the dynamic behavior of nano-bubbles near the surface of single crystal iron (Fe) was investigated using molecular dynamics simulations. The cavitation erosion behavior of single crystal Fe and the structural evolution of its eroded surface was examined at different bubble diameters. The results show that nano-bubble diameter is inversely correlated with impact pressure and diameter is positively correlated with nanojet energy. The volume, surface area, and depth of cavitation pits are nearly directly proportional to the bubble diameter with correlation linear fitting coefficients of R2 = 0.9837, R2 = 0.9922, and R2 = 0.9799, respectively. Additionally, cavitation erosion induces the structural evolution of iron atoms from bcc to fcc and hcp structures. The percentage of new phase transformed is related to the bubble diameter and the type of transformed structure, the percentage of fcc and hcp structures of Fe atoms exhibits an increasing trend with the increase in the bubble diameter, and the Fe atoms of fcc structures occur an obvious increase beyond a bubble diameter of 12 nm.

Microscopic effect of iron dosage on the stability of Fe‐doped ettringite

Microscopic effect of iron dosage on the stability of Fe‐doped ettringite

Bifunctional activity and theoretical study of transition metal molybdates for hydrogen and oxygen evolution reaction

Effective, sturdy and cheap electrocatalysts are extremely desirable for water electrolysis. In this work, transition metal molybdates (MMoO4, M = Fe, Co, Ni) with extraordinary oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in basic electrolyte solution was reported. β-Fe2(MoO4)3 catalyst exhibits better electrocatalytic performance and robustness for both HER and OER compared to NiMoO4 and CoMoO4. Theoretical study (DFT calculation) disclose that the Fe atoms increase the energy states near the Fermi level in β-Fe2(MoO4)3 which makes it more conductive leading to superior OER and HER activity. Compared to CoMoO4 and NiMoO4, β-Fe2(MoO4)3 have well defined multiple Mo 4d orbitals at the conduction band. These are empty states in conduction band, ready to receive the electrons. Further, the computed overpotential values for NiMoO4, CoMoO4, and β-Fe2(MoO4)3 surfaces follow the trend, β-Fe2(MoO4)3 < NiMoO4 < CoMoO4, corroborating with the experimental results.

Exploring the impact of S-doped Fe-N-C materials on the ORR mechanism within a constant potential solvation model

The widespread application of S doping in Fe-N-C materials aims to enhance the catalytic activity for oxygen reduction reactions (ORR). However, the current doping strategies are primarily centered on the first coordination layer encompassing Fe atoms. Consequently, this study employs first-principles calculations to compute the formation and binding energies of FeN4 doped with S atom. It further delves into the influence of diverse doping sites on catalyst stability and meticulously analyzes the configurations and corresponding ORR activities of four catalysts, namely FeN4S-N (Number=0∼3), utilizing a constant-potential implicit solvent model to simulate authentic electrocatalytic environments. The findings reveal that under vacuum conditions, FeN4S1 exhibits the utmost ORR activity, boasting a potential of 0.53 V. Conversely, within the constant-potential implicit solvation model, FeN4S2 emerges as the catalyst with the highest ORR activity, achieving a potential of 0.39 V. Therefore, calculations leveraging the constant-potential solvation model offer more realistic insights into catalyst design, thereby guiding the development of superior catalysts.

Spin Effect to Regulate the Electronic Structure of Ir─Fe Aerogels for Efficient Acidic Water Oxidation.

"Spin" has been recently reported as an important degree of electronic freedom to promote catalysis, yet how it influences electronic structure remains unexplored. This work reports the spin-induced orbital hybridization in Ir─Fe bimetallic aerogels, where the electronic structure of Ir sites is effectively regulated by tuning the spin property of Fe atoms. The spin-optimized electronic structure boosts oxygen evolution reaction (OER) electrocatalysis in acidic media, resulting in a largely improved catalytic performance with an overpotential of as low as 236mV at 10mAcm-2. Furthermore, the gelation kinetics for the aerogel synthesis is improved by an order of magnitude based on the introduction of a magnetic field. Density functional theory calculation reveals that the increased magnetic moment of Fe (3d orbital) changes the d-band structure (i.e., the d-band center and bandwidth) of Ir (5d orbital) via orbital hybridization, resulting in optimized binding of reaction intermediates. This strategy builds the bridge between the electron spin theory with the d-band theory and provides a new way for the design of high-performance electrocatalysts by using spin-induced orbital interaction.

Key coordination of oxygen doping in Fe single-atoms enhances nonradical activation of peroxymonosulfate: The formation of high-valent Fe species and electron transfer

Modulating the coordination environments and the electronic configurations of the metal centers of single-atom catalysts (SACs) to further improve the activation of peroxomonosulfate (PMS) remains a great challenge. In this work, oxygen (O) atoms were doped into Fe-N4 single-atom catalysts via oxygen-containing acid precursors to adjust the electronic structure to enhance PMS activation. The prepared Fe-N4O single-atom catalysts exhibited excellent oxidation capacity, tolerance, elevated stability and continuous organic oxidation. The primary degradation pathway is the high-valent iron (Fe IV = O) and the electron transfer mechanism. DFT calculations indicated that the adsorption energy and electron transfer number of second-shell-coordinated Fe-N4O were much higher than those of one-shell-coordinated Fe-N3O. The introduction of O atoms increased the electron density of the central Fe atoms and the electron delocalization domains, which increased the electron transfer capacity. This research provides a method to finely control the coordination environment and electronic structure of Fe-N4, revealing the unique dynamic regulation mechanism of heteroatoms for advanced oxidation, and providing a reference for the design of high-efficiency Fenton-like-based catalysts.

Ferromagnetism with above-room-temperature Curie temperature in Fe-doped β-Ga2O3 studied by first-principles calculations

Induced by the spin-polarized double-exchange interaction between the 3d orbitals of Fe atoms and O-2p orbitals near the O/Ga vacancy complexes, the origin of magnetism in β-Ga2O3 is investigated by using geometry optimization and energy calculation based on the first-principles generalized gradient approximation Hubbard + U method of density-functional theory. The results show that the formation energy of Fe2+ in the β-Ga2O3 matrix is lower than that of Fe3+, and the system is more stable when the Ga or O vacancies (VGa or VO) are adjacent to the Fe lattice position. It is found that the β-Ga31Fe2+/3+O47 and β-Ga30Fe2+/3+O48 systems all exhibit ferromagnetism with above-room-temperature Curie temperature. β-Ga30Fe2+/3+O48 (i.e., with Fe2+/3+ and VGa) has more spin-polarized O atoms in the same direction. The magnetism originates from the double-exchange interaction of the coupling and hybridization of the Fe-3d state of Fe3+ and the O-2p state, which increases the magnetic moment of the β-Ga30Fe3+O48 system. This study provides a theoretical reference for designing and preparing new β-Ga2O3-based dilute magnetic semiconductors and related spintronic and optoelectronic devices.

Effects of Mo doping on the structure, adsorption performance, and photocatalytic activity of LaFeO3 nanoparticles: Experimental and DFT studies

In this study, a series of Mo-doped LaFeO3 composite photocatalyst nanoparticles (x-LFMO, x = 0.33, 0.5, 0.67) were synthesized by ultrasonic-assisted sol–gel method under controlled Mo doping. X-ray diffraction (XRD) analyses indicate that Mo substitutes one-third of the Fe atoms in the B site of the LaFeO3 to form orthogonal perovskite structures LaFe0.67Mo0.33O3, which is the only pure phase crystal formed at stoichiometric Fe to Mo ratios of 2:1, 1:1, and 1:2, respectively. SEM and N2 adsorption/desorption revealed significantly smaller particle sizes (30–50 nm) and the formation of hollow structures and rich channels after Mo doping, thus enriching the specific surface area and pore size dispersion. DRS confirmed that the Mo-doped LFO composites exhibit significantly enhanced absorption in the visible region. This can be further explained by DFT theoretical calculations of energy band structures and density of states, which demonstrate that the effective mass of the electrons in LaFe0.67Mo0.33O3 is reduced and the off-domain properties of the electrons are enhanced, facilitating the excitation and transport of the photogenerated electrons. Kinetic studies showed that Mo-doped composite nanoparticles exhibit excellent adsorption capacity for quinoline, indole, and pyridine, and the pure phase LaFe0.67Mo0.33O3 and 0.5-LFMO performed well for them with removal efficiencies (>98 %) under visible light irradiation. Based on experimental observations and theoretical insights, it is suggested that the higher quantum yield and photocatalytic reactivity of x-LFMO composites are attributed to the bulk oxygen mobility and surface oxygen reactivity promoted by the octahedral distortion of BO6 in LaFe0.67Mo0.33O3 and the heterogeneous structure formed at the interface of the two phases.

First-principles study of electronic and magnetic properties in site dependent Fe-doped chalcopyrite ZnSnAs2semiconductors: Comparison with those of Mn- and Cr-doped ZnSnAs2

The electronic and magnetic properties of Fe-doped ZnSnAs2 within chalcopyrite structures have been studied by first-principles calculations using the density functional theory (DFT) full-potential linearized augmented-plane-wave method and the plane-wave pseudopotential methods. The band gap of ZnSnAs2 was determined to be 0.816 eV using the modified Beck-Jonson (mBJ) exchange potential. When Fe dopants substitutionally replace Sn atoms, half-metallic ferromagnetism is observed in ZnSnAs2 where in the spin-down band at the Fermi level is entirely unoccupied. The magnetic exchange interaction between two Fe atoms substituting Zn and Sn sites in the supercell with different geometries has been studied. The total energy difference (ΔE) between the antiferromagnetic (AFM) and ferromagnetic (FM) configurations suggests that Fe atom occupation of Zn sites in ZnSnAs2 leads to a predominantly AFM state, while the Fe atom occupation of Sn sites prefers the FM state.

Preparation Fe–N–C catalyst for ORR with high pyridine-type FeN4 based on nano-SiO2 shell coating method

In this paper, we present a method to enhance the stability of Fe–N–C electrocatalysts, known for their significant oxygen reduction reaction (ORR) activity and positioned as promising alternatives to commercial noble metal-based catalysts. Despite the favorable ORR activity, Fe–N–C suffers from inadequate stability in acidic media, primarily attributed the loss of active FeN4 sites resulted from Fe-demetalation. However, recent investigation reveals that pyridine N exhibits remarkable stability in retaining Fe atoms. To address this, we achieved a high proportion of pyridine N doping in carbon nanofibers through a process involving nano-SiO2 shell coating and electrospinning. The nano-SiO2 shell coating method demonstrates efficacy and versatility in transforming pyrrole-type FeN4 into pyridine-type FeN4, irrespective of the origin material being trivalent or divalent Fe, whether organic or inorganic.

Potentially toxic elements distribution, petrography, and synchrotron characterization in polluted soils around industrial complex, Central Jordan

Industry is the main source of soil pollution in Jordan, where higher concentrations of potentially toxic elements were found in the soil around industrial estates. This study is dealing with an industrial pollution hot spot that is a steel factory in central Jordan that emits various ashes and gases. This area is moderately inhibited, and its soil is increasingly utilized in agricultural activities. High Fe, Cr, Mn, Pb, and V contents were recorded in the soil adjacent to the factory mainly concentrated on the prevailing wind direction. The studied sites bear heavy metalloids concentrations exceeding the permissible limit of WHO/EPA. These concentrations were found in topsoils and they decreased downward because of low mobility due of high soil alkalinity and lower pedogenesis. Moreover, the synchrotron-based XAFS technique was used to understand changes in oxidation states of Fe atom as well as in its structural parameters with depth. EXAFS analysis reveals association of Fe atoms mainly with oxygen (O), which indicates the anthropogenic Fe source. XANES data shows that Fe occurs in divalent (Fe2+) and trivalent (Fe3+) forms, which indicates that magnetite is dominating the topsoil. This Fe-phase is usually formed during oxygenated high thermal manufacturing processes. The topsoils SEM-EDS investigations confirmed the dominance of magnetite spheres, which coincides with the positive correlation between Fe and other elements as indicated from the statistical interpretation of the data.