Fe Bond Research Articles

Equation of State, Structure, and Transport Properties of Iron Hydride Melts at Planetary Interior Conditions

AbstractIron hydrides are a potentially dominant component of the metallic cores of planets, primarily because of hydrogen's ubiquity in the universe and affinity for iron. Using ab initio molecular dynamics, we examine iron hydrides with 0.1, 0.33, 0.5, and 0.6 mol fraction hydrogen up to 100 GPa between 3,000 and 5,000 K to describe how hydrogen content affects the melt structure, hydrogen speciation, equation of state (EOS), atomic diffusivity, and melt viscosity. We find that the addition of hydrogen decreases the average Fe–Fe coordination number and lengthens Fe–Fe bonds, while Fe–H coordination number increases. The pair distribution function of hydrogen at low pressure indicates the presence of molecular hydrogen. By tracking chemical speciation, we show that the amount of molecular hydrogen increases and the number of iron in Hx≥1Fey≥0 clusters decreases as the hydrogen concentration increases. We parameterize a pressure, volume, temperature, and composition EOS and show that the molar volume and Grüneisen parameter of the melts decrease while the compressibility and thermal expansivity increase as a function of hydrogen concentration. We find that hydrogen acts as a lubricant in the melts as the iron and hydrogen become more diffusive and the melts become more inviscid as the hydrogen concentration increases. We estimate 2.7 wt% hydrogen in the Martian core and 0.49–1.1 wt% hydrogen in Earth's outer core based on comparisons to seismic models, with the assumption that the cores are pure liquid iron‐hydrogen alloy, and we compare the small exoplanet population with mass‐radius curves of iron hydride planets.

Tailoring Ni-Fe-B Electronic Effects in Layered Double Hydroxides for Enhanced Oxygen Evolution Activity.

NiFe layered double hydroxides (LDHs) are state-of-the-art catalysts for the oxygen evolution reaction (OER) in alkaline media, yet they still face significant overpotentials. Here, quantitative boron (B) doping is introduced in NiFe LDHs (ranging from 0% to 20.3%) to effectively tailor the Ni-Fe-B electronic interactions for enhanced OER performance. The co-hydrolysis synthesis approach synchronizes the hydrolysis rates of Ni and Fe precursors with the formation rate of B─O─M (M: Ni, Fe) bonds, ensuring precise B doping into the NiFe LDHs. It is demonstrated that B, as an electron-deficient element, acts as an "electron sink" at doping levels from 0% to 13.5%, facilitating the transition of Ni2+ to the active Ni3+δ, thereby accelerating OER kinetics. However, excessive B doping (13.5-20.3%) effectively generates oxygen vacancies in the LDHs, which increases electron density at Ni2+ sites and hinders their transition to Ni3+δ, thereby reducing OER activity. Optimal OER performance is achieved at a B doping level of 13.5%, with an overpotential of only 208mV to reach a current density of 500mA cm-2, placing it among the most effective OER catalysts to date. This Ni-Fe-B electronic engineering opens new avenues for developing highly efficient anode catalysts for water-splitting hydrogen production.

Sonoelectrochemical degradation of aspirin in aquatic medium using ozone and peroxymonosulfate activated with FeS2 nanoparticles

The catalytic performance of nano-FeS2 in the sonoelectrochemical activation of peroxymonosulfate (PMS) and ozone to remove aspirin (ASP) was studied for the first time. The crystal structure and Fe bonds in the catalyst were confirmed through XRD and FTIR analysis. Within 30 min, ASP (TOC) was removed by 99.2 % (81.6 %) and 98.6 % (77.4 %) in nano-FeS2/PMS and nano-FeS2/O3 sonoelectrochemical systems, respectively. Water anions, especiallyHCO3− (almost 50 %), had an inhibitory effect on ASP removal. The probes confirmed that SO4•−and HO• were the key to ASP degradation in nano-FeS2/PMS and nano-FeS2/O3 systems, respectively. The effective activation of oxidants due to the ideal distribution of Fe2+ by catalyst was the main mechanism of ASP removal, in which electric current (EC) and ultrasound (US) played a crucial role through the recycling of Fe ions, dissolution and cleaning of the catalyst. LC-MS analysis identified thirteen byproducts in the ASP degradation pathways. The energy consumption of the proposed sonoelectrochemical systems was lower than previous similar systems. This study presented economic and sustainable hybrid systems for pharmaceutical wastewater remediation.

The green approach of chitosan/Fe2O3/ZnO-nanocomposite synthesis with an evaluation of its biological activities

Biopolymers embedded with nanoparticles of metal oxides (MOs) demonstrate a wide range of bio-functions. Chitosan-incorporated MOs are an interesting class of support matrices for enhancing the biological function, compared to other support matrices. Therefore, the importance of this study lies in exploiting chitosan as a carrier not of one metal as in previous studies, but of two metals in the form of a nanocomposite to carry out several biological functions. The coprecipitation approach was employed to synthesize chitosan/Fe2O3/ZnO-nanocomposite in the present research. The characterization of chitosan/Fe2O3/ZnO-nanocomposite was performed to find out the morphology and dispersion properties of chitosan/Fe2O3/ZnO-nanocomposite. The X-ray diffraction (XRD) investigation revealed that these were crystalline. Fourier transforms infrared (FTIR) spectrum bands were viewed at 400/cm and 900/cm, due to the stretching vibration of Fe and Zn oxygen bond. TEM showed that chitosan/Fe2O3/ZnO-nanocomposite was of 20–95 nm in size. chitosan/Fe2O3/ZnO-nanocomposite exhibited inhibitory potential against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Candida albicans with inhibition zones of 25 ± 0.1, 28 ± 0.2, 27 ± 0.1, and 27 ± 0.2 mm, respectively while didn’t inhibited Aspergillus niger. MIC value of nanocomposite was 15.62 ± 0.33 µg/mL for C. albicans, B. subtilis and E. coli, while it was 62.50 ± 0.66 µg/mL for Pseudomonas aeruginosa. Ranged values of nanocomposite MBC (15.62 ± 0.33 to 125 ± 1 µg/mL) were attributed to all tested bacteria. Different concentrations of chitosan/Fe2O3/ZnO-nanocomposite MBC (25, 50, and 75%) reflected anti-biofilm activity against E. coli (85.0, 93.2, and 96.0%), B. subtilis (84.88, 92.21, and 96.99%), S. aureus 81.64, 90.52, and 94.64%) and P. aurogenosa (90.11, 94.43, and 98.24%), respectively. The differences in the levels of antimicrobial activities may depend on the type of examined microbes. Antioxidant activity of chitosan/Fe2O3/ZnO-nanocomposite was recorded with excellent IC50 values of 16.06 and 32.6 µg/mL using DPPH and ABTS scavenging, respectively. Wound heal by chitosan/Fe2O3/ZnO-nanocomposite was achieved with 100% compared to the untreated cells (76.75% of wound closer). The cytotoxicity outcomes showed that the IC50 of the chitosan/Fe2O3/ZnO-nanocomposite was 564.32 ± 1.46 µg/mL normal WI-38 cells. Based on the achieved findings, the chitosan/Fe2O3/ZnO-nanocomposite is a very promising agent for perform pharmacological activities.

(Invited) Atomically Dispersed Metal Electrocatalysts for CO2 to CO Conversion: From Single to Dual Metal Sites

Carbon-supported nitrogen-coordinated single-metal site catalysts (i.e., M−N−C, M: Fe, Co, or Ni) are active for the electrochemical CO2 reduction reaction (CO2RR) to CO.(1) We comprehensively engineered FeN4 and NiNx sites for electrochemical CO2 reduction to CO considering the particle sizes of the catalysts, metal content, and the M−N (M: Fe or Ni) bond structures.(2, 3)The unique M-N-C model allows us to elucidate each factor′s role exclusively regarding the promotion of CO2 reduction.(4)Optimal particle sizes and Fe content provide favorable external factors to improve mass activity. Structural changes of M−N bonds controlled by thermal activation temperatures can intrinsically enhance CO selectivity and kinetic activity. Notably, the NiN3 active sites with optimal local structures formed at higher temperatures (e.g., 1200 °C) are intrinsically more active and CO-selective than NiN4, providing a new opportunity to design a highly active catalyst via populating NiN3 sites with increased density. Further improving their intrinsic activity and selectivity by tuning their N−M bond structures and coordination is limited. We further expand the coordination environments of M−N−C catalysts by designing dual-metal active sites.(5)The Ni-Fe catalyst exhibited the most efficient CO2RR activity and promising stability compared to other combinations. Advanced structural characterization and theoretical prediction suggest that the most active N-coordinated dual-metal site configurations are 2N-bridged (Fe-Ni)N6, in which FeN4 and NiN4 moieties are shared with two N atoms. Two metals (i.e., Fe and Ni) in the dual-metal site likely generate a synergy to enable more optimal *COOH adsorption and *CO desorption than single-metal sites (FeN4 or NiN4) with improved intrinsic catalytic activity and selectivity.References Pan F, Zhang H, Liu K, Cullen D, More K, Wang M, et al. Unveiling Active Sites of CO2 Reduction on Nitrogen-Coordinated and Atomically Dispersed Iron and Cobalt Catalysts. ACS Catalysis. 2018;8(4):3116-22.Li Y, Adli NM, Shan W, Wang M, Zachman MJ, Hwang S, et al. Atomically dispersed single Ni site catalysts for high-efficiency CO2 electroreduction at industrial-level current densities. Energy & Environmental Science. 2022;15(5):2108-19.Mohd Adli N, Shan W, Hwang S, Samarakoon W, Karakalos S, Li Y, et al. Engineering Atomically Dispersed FeN4 Active Sites for CO2 Electroreduction. Angewandte Chemie International Edition. 2021;60(2):1022-32.Li J, Zhang H, Samarakoon W, Shan W, Cullen DA, Karakalos S, et al. Thermally Driven Structure and Performance Evolution of Atomically Dispersed FeN4 Sites for Oxygen Reduction. Angewandte Chemie International Edition. 2019;58(52):18971-80.Li Y, Shan W, Zachman MJ, Wang M, Hwang S, Tabassum H, et al. Atomically Dispersed Dual-Metal Site Catalysts for Enhanced CO2 Reduction: Mechanistic Insight into Active Site Structures. Angewandte Chemie International Edition. 2022;61(28):e202205632.

Controllable Growth of Crystal Facets Enables Superb Cycling Stability of Anode Material for Potassium Ion Batteries

AbstractTo enrich the crystal growth strategies for the booming applications concerning lattice structure, a preferred facet‐growth method is proposed for solvothermal synthesis of target (BiO)2CO3 in the two‐phase system. The dominant crystal phase can be regulated from α‐Fe2O3 to (BiO)2CO3 by properly increasing dosage of Bi feedstock, and the optimized composite is composed of (BiO)2CO3 nanocrystal (≈10 nm) and amorphous iron oxide (defined as “FOB‐50”). Based on experimental characterizations and theoretical calculations, the highly matched lattice between (006)/(0012) facets of α‐Fe2O3 and {010} facet group of (BiO)2CO3 involving orientation of Fe─O─Fe bond and Bi─O─Bi bond is verified to facilitate the interaction between the above facets, resulting in preferred growth of {010} dominated by (040) facet in (BiO)2CO3 and its composites. The structural merits can not only enable the FOB‐50‐based electrodes to achieve a high capacity and unprecedentedly stable cyclic performances for 1500 cycles/a long time‐span of 32 months as anode materials, but also ensure the full‐cell to well inherit the electrochemical features of the cathode in potassium ion batteries (PIBs). This work can provide new insight into lattice regulation for bismuth‐based materials and expand their application as electrodes for high performance PIBs and lithium ion batteries.

Bridge-oxygen bonding modulates Ru single atoms for peroxymonosulfate activation: Importance of high-valent Ru species and 1O2

The application of single-atom catalysts (SACs) to advanced oxidation processes (AOPs) based on peroxymonosulfate (PMS) has attracted considerable attention. However, the catalytic pathways and mechanisms underlying these processes remain unclear. In this study, NiFe-LDH was synthesized and single Ru atoms were stably loaded onto it by forming Ru–O–M (M=Ni or Fe) bonds (Ru@NiFe-LDH). This was demonstrated using high-angle annular dark-field scanning TEM (HAADF-STEM) and X-ray absorption fine structure spectra (XANES). The Ru@NiFe-LDH/PMS system showed a high catalytic reactivity (100 % sulfamethoxazole degradation in only 30 min), high stability (97 % reactivity was maintained after continuous operation for 400 min), and wide pH suitability (working pH range 3–11) for AOPs. The crucial roles of the high-valent species (Ru(V) = O) and 1O2 in this reaction were verified. Density functional theory (DFT) calculations revealed that electron transfer produced a positively charged Ru. This enhances the adsorption of negatively charged PMS anions onto the Ru monoatomic sites, thereby, causing the formation of Ru-PMS* complexes. This study implies that the structure–function relationship between organic compounds and SACs plays a significant role in PMS-based AOPs, and provides a comprehensive mechanism for the role of high-valent species in heterogeneous Fenton-like systems.

Crystal structure-dependent evaluation of chloride ions resistance of iron passivation film in reinforced concrete at the nanoscale

In reinforced concrete, the passivation film refers to the spontaneous formation of an ultra-thin film of corrosion product on a metal's surface that acts as a barrier to additional chemical reactions and is extraordinarily helpful in mitigating corrosion damage. However, the Cl ions can significantly harm the completeness of the passivation film and thus facilitate the corrosion process. In view of the complexity of the passivation film composition, in this work, the Cl attack process of typical structures of passivation films (α-Fe2O3, β-Fe2O3 and γ-Fe2O3) is studied by Bonn-Oppenheimer molecular dynamics and density functional theory. It is found that the β-Fe2O3 and γ-Fe2O3 have the best and worst resistance of Cl ions, respectively. The reduced gradient density analyses indicate that the Cl ions can break chemical bonds of passivation film by creating Cl–Fe bonds. The details of binding energy and electron localization analyses prove that the rank of the strength of binding is γ-Fe2O3 > α-Fe2O3 > β-Fe2O3. Moreover, Different from the surface adsorption of α-Fe2O3 and β-Fe2O3, γ-Fe2O3 adsorbs Cl ions into the matrix, which also results in the formation of more chemical bonds. Further analyses of the density of states also confirm the bonding formation in the Cl ions attack process. This work suggests that the increase in the proportion of β-Fe2O3 in the composition of the passivation film is a potential approach for inhibiting corrosion. And also an effective method for evaluating the performance of passivation films is also proposed, especially since it is extremely difficult to evaluate given its nanometer characteristics.

Insight into the TiO2 on transport behavior and heat transfer of the CaO–SiO2–FeO–MgO system at different basicities: Molecular dynamics simulation and thermodynamics

In order to promote the resource utilization of Ti-containing converter slag and reduce the loss of metallic Ti, it is necessary to clarify the relationship between the oxygen network structure and thermophysical properties of the slag. The present work uses classical molecular dynamics (CMD) simulation to study the effects of basicity (1.0–3.0) and TiO2 content (0%–10 %) on the local structural properties, viscosity, and thermal conductivity of the CaO–SiO2–FeO–MgO–TiO2 (CSFMT) system at 1873 K. The M − O (M = Ca, Si, Fe, Mg, and Ti) bond length calculated based on CMD is consistent with the experimental results, and the [SiO4] tetrahedron and [TiO6] octahedron are the basic structural units of the CSFMT system. The increase in basicity promotes the break of bridging oxygen (BO) Si–O–Si and the formation of non-bridging oxygen Si–O-M. The increase in TiO2 content promotes the formation of Ti–O–Si in the system. The basicity and TiO2 content affect the thermophysical properties of the CSFMT system by promoting and inhibiting the depolymerization of the oxygen network structure, respectively. The diffusion abilities of different atoms in the CSFMT system are in descending order of Fe > Mg > Ca > O > Si > Ti. The viscosity of the CSFMT system decreases with increasing basicity and increases with increasing TiO2 content. Increasing the proportion of BOs can weaken the anharmonicity in the polyhedral structural units and reduce phonon scattering. With increasing basicity and TiO2 content, the effective phonon mean free path decreases and increases, respectively, resulting in a decrease and an increase in the thermal conductivity of the CSFMT system. The changes in the microstructure properties of the CSFMT system can be reasonably explained by the changes in its thermodynamic properties such as enthalpy. It is worth noting that the basicity has a greater effect on the viscosity, while the TiO2 content has a more significant impact on the thermal conductivity of the CSFMT system.

Fabrication and evaluation of high-entropy alloy reinforced Fe bond diamond tool

Metal-bond diamond tools find extensive use in the grinding of hard and brittle materials. The mechanical properties and wear resistance of the metal bond are crucial for the grinding performance and life of diamond tools. However, Fe bonds exhibit insufficient hardness, strength, and wear resistance, and existing reinforcement methods are difficult to simultaneously improve the self-sharpness and wear resistance of diamond tools, leading to a trade-off between grinding performance and life. In this paper, a novel AlCoCrFeNi HEA particles reinforced Fe (HEA/Fe) alloy was proposed as the bond for diamond tool to address the aforementioned issue. The work considers materials science fundamentals related to the element diffusion mechanism and particle reinforcement mechanism in the design of the HEA/Fe bond. Through the mutual element diffusion between the HEA and Fe matrix, expanded HEA regions are formed, which not only enhance the strength and overall wear resistance of the HEA/Fe bond but also generate a composite structure with varying hardness. The distinct mechanical properties of composite structure form wear-resistant and non-wear-resistant areas within the diamond tool, effectively balancing the challenging trade-off between wear resistance and self-sharpness. This allows HEA/Fe bond diamond tools to achieve both prolonged service life and high grinding performance. The results reveal that the HEA/Fe bond diamond tool exhibits a lower grinding force, a superior surface finish, and a nearly equivalent grinding ratio compared to the commercial Fe-based alloy bond diamond tool in grinding of sapphire.

High temperature transformations and thermal expansion of halotrichite FeAl<sub>2</sub> (SO<sub>4</sub>)<sub>4</sub>⋅22H<sub>2</sub>O

Halotrichite is a widespread mineral in post-volcanic environments and oxidation zones of ore deposits. Halotrichite is stable at temperature up to 70 °C; further heating leads to the formation of an X-ray amorphous phase I. There are reflections of millosevichite (prevailing) and mikasaite appearing in the range of temperatures 340–660 °C. Millosevichite and mikasaite are decomposing at temperatures 660 °C with the formation of an X-ray amorphous phase II. According to data of the synchronous thermal analysis, the transition from halotrichite into anhydrous sulfates is accompanied by the loss of H2O molecules, which makes about 42.9 wt %, the transition to the X-ray amorphous phase II is caused by the loss of SO3, which is ca. 37.4 wt %, associated with two endothermal effects. The thermal expansion of halotrichite is sharply anisotropic, the maximum expansion is determined by the shear deformations of the lattice in its monoclinic plane along the bisectrix of the obtuse angle β, and the minimum one – in the direction of strong S–O–Fe bonds inside [Fe(SO4)(H2O)5]0 complexes. The significant volumetric expansion of halotrichite (9(3)∙10-5 ºC-1) occurs due to the determing role of hydrogen bonds in composition of the crystal structure.

Synthesis of lithium doped magnesium ferrites and their vibrational and magnetic properties: Correlation of experimental and density functional theory

Recently, there has been an increased focus on investigating the possible use of ferrite nanoparticles as magnetic memory devices. In this study, we report on the structural, microstructural, Raman, density functional theory and magnetic characteristics of Mg1-xLixFe2O4 (x = 0, 0.15, 0.3, 0.45, 0.5 and 0.75). Samples were synthesized by solution combustion synthesis method. Samples were subjected to characterize X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman Spectra. XRD reveals that all synthesized samples show a single phase formation and unit cell volume, crystallite size varied with an increase in Lithium-ion concentration. SEM micrographs confirmed the porous nature increases with the rise of Li concentration. Particles are agglomeration and spherical type of nature was confirmed by TEM images. Further, Raman Spectra confirms the spinel cubic structure of MgFe2O4 nanoparticles belongs to the Fd3m space group. Despite the fact that the full unit cell has 56 atoms (Z = 8), the smallest Bravais cell consists of only 14 atoms (Z = 2). Consequently, in order to understand this effect, the electronic structure of pure and doped models was investigated through the Band Structure and Density of States (D.O.S.) profiles. First the crystalline structure of pure and Li-doped MgFe2O4 was analyzed based on the optimized lattice parameters and M − O (M = Mg, Li and Fe) bond distances. The band-gap was computed to be 2.54 eV being a direct transition between two points, in an excellent agreement with the experimental measurements. To investigate the temperature dependent magnetic properties, the M − H loops of Li doped MgFe2O4 nanoparticles traced at below and above room temperature over the applied magnetic field ±60 kOe. The M − H loops recorded at above and below room temperature demonstrated that the ferromagnetic nature of the sample. Further, the magnetic properties was investigated using temperature dependent FC and ZFC magnetization measurements. Above room temperature, the ZFC and FC curves show irreversibility and split at certain temperatures, as well as a broad maximum in ZFC curves at blocking temperature (TB). Saturation magnetization (Ms) values are higher at 15 K compared to 300 K, attributed to reduced thermal fluctuation. Our results suggest that synthesized materials are useful for room temperature magnetic memory device application.

The Formation of Phytic Acid–Silane Films on Cold-Rolled Steel and Corrosion Resistance

In this work, phytic acid (PA) and 3-mercaptopropyltrimethoxysilane (MPTS) underwent a condensation process to produce a phytic acid–silane (abbreviated PAS) passivation solution. Additionally, it was applied to the surface of cold-rolled steel to create a composite phytic acid–silane film. The functional groups of the passivation solution were analyzed by Fourier transform infrared spectroscopy (FT-IR). The composite film was evaluated using an electrochemical workstation, scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS) and pull-off test. These techniques allowed for the characterization of the film’s micromorphology, oxidation, chemical composition and adhesion strength. The results show that the PAS composite film provides higher protection efficiency compared to cold-rolled steel substrates, low phosphorus passivation films, single phytate passivation films and commercial phosphate films. This composite film also has a higher adhesion strength, which is beneficial for subsequent coating, and a possible corrosion resistance mechanism was proposed as well. The PAS layer successfully prevents the penetration of corrosive media into the cold-rolled steel surface utilizing P–O–Fe bonds, thus improving the corrosion barrier effect of the substrate.

Effects of Mn on the interface bonding and mechanical properties of TiC reinforced steel matrix composites

The addition of alloying elements to the steel matrix during the preparation process can significantly affect the properties of TiC reinforced steel matrix composites. In this study, the effects of Mn on the electronic structure and crystal structure stability of Fe supercells, along with as well as the stability of the TiC/Fe(Mn) interface, were analyzed through first-principles calculations. Additionally, 8 vol% TiC/Fe–C composites were prepared through the master alloy method. The effects of Mn contents (0, 0.8, 1.2, 1.6, and 2.0 wt%) on the interface mismatch and mechanical properties of the composites were investigated. The results revealed that Mn formed a solid solution and generated a stronger Fe–Mn bond compared with the Fe–Fe bond, and no interface chemical reaction occurred. The addition of a small amount of Mn improved the interface bonding between TiC particles and the steel matrix. The TiC particles were uniformly distributed in the matrix at the grain boundaries, with only a small amount dispersed within the grains. The TiC particles and steel matrix exhibited excellent, continuous, and stable interface bonding. The addition of Mn reduced the interface mismatch between TiC particles and the matrix. As the Mn content increased, the tensile strength and elongation of the composites first increased and then decreased, while the hardness of the composites increased. The addition of 1.2 wt% Mn resulted in an increase in the tensile strength, elongation, and hardness of the composite by 1160 MPa, 7.3%, and 43 HRC, respectively. These values were 109.8%, 151.7%, and 31.1% higher than those of the composite without Mn addition. However, an excess of Mn led to severe distortion of the Fe lattice and clustering at the interface, resulting in the degradation of the mechanical properties in the composites.

Hetero MOF‐On‐MOF of Ni‐BDC/NH2‐MIL‐88B(Fe) Enables Efficient Electrochemical Seawater Oxidation

AbstractSeawater electrolysis is a sustainable technology for producing hydrogen that would neither cause global freshwater shortages nor create carbon emissions. However, this technology is severely hampered by the insufficient stability and the competition from the chlorine evolution reaction (ClER) in actual application. Herein, a metal–organic framework (MOF)‐on‐MOF heterojunction (Ni‐BDC/NH2‐MIL‐88B(Fe)) denoted as (Ni‐BDC/NM88B(Fe)) is synthesized as an effective oxygen evolution reaction (OER) electrocatalyst for high‐performance seawater electrolysis, which exhibits a long stability of 200 h and low overpotentials of 232 and 299 mV at 100 mA cm−2 in alkaline freshwater and seawater solution, respectively. The exceptional performance is attributed to the rapid self‐reconstruction of Ni‐BDC/NM88B(Fe) to produce NiFeOOH protective layer, thereby avoiding ClER‐induced dissolution. Moreover, the interface interaction between Ni‐BDC and NM88B(Fe) could form the Ni─O─Fe bonds in Ni‐BDC/NM88B(Fe) to promote the electron transfer and lower the energy barrier of the rate‐determining step, thereby accelerating the OER. These electrochemical properties make it intriguing candidate as an efficient electrocatalyst for practical alkaline seawater electrolysis.

The change of coordination environments induced by vacancy defects in hematite leads to a contrasting difference between cation Pb(II) and oxyanion As(V) immobilization

Hematite is an iron oxide commonly found in terrestrial environments and plays an essential role in controlling the migration of heavy metal(loid)s in groundwater and sediments. Although defects were shown to exist both in naturally occurring and laboratory-synthesized hematite, their influences on the immobilization of heavy metal(loid)s remain poorly understood. In this study, hematite samples with tunable vacancy defect concentrations were synthesized to evaluate their adsorption capacities for the cation Pb(II) and for the oxyanion As(V). The defects in hematite were characterized using XRD, TEM-EDS mapping, position annihilation lifetime spectroscopy, and XAS. The surface charge characteristics in defective hematite were investigated using zeta potential measurements. We found that Fe vacancies were the primary defect type in the hematite structure. Batch experiments confirmed that Fe vacancies in hematite promoted As(V) adsorption, while they decreased Pb(II) adsorption. The reason for the opposite effects of Fe vacancies on Pb(II) and As(V) immobilization was investigated using DFT calculations and EXAFS analysis. The results revealed that Fe vacancies altered As–Fe coordination from a monodentate to a bidentate complex and increased the length of the Pb–Fe bond on the hematite surface, thereby leading to an increase in As(V) bonding strength, while decreasing Pb(II) adsorption affinity. In addition, the zeta potential analysis demonstrated that the presence of Fe vacancies led to an increase in the isoelectric point (IEP) of hematite samples, which therefore decreased the attraction for the cation Pb(II) and increased the attraction for the oxyanion As(V). The combination of these two effects caused by defects contributed to the contrasting difference between cation Pb(II) and oxyanion As(V) immobilization by defective hematite. Our study therefore provides new insights into the migration and fate of toxic heavy metal(loid)s controlled by iron minerals.

Influence of long- and short-range chemical order on spontaneous magnetization in single-crystalline Fe0.6Al0.4 compound thin films

We systematically investigate the long- and short-range chemical order, lattice volume, and spontaneous magnetization in single-crystalline Fe0.6Al0.4 compound thin films. The vapor-quenching method based on a molecular beam epitaxy technique is utilized to fabricate the single-crystalline Fe0.6Al0.4 compound with the different B2 long-range order parameter S. S was varied by the deposition temperature T d, and it increases with increasing T d. The lattice volume V decreased with increasing T d, while the tetragonal distortion, ∼4%, due to epitaxial strain were observed. The changes in S and V were accompanied with the change in the magnetic moment per Fe, μ Fe. μ Fe showed the monotonic decrease as a function of S whereas μ Fe monotonically increases with V. With considering tetragonal distortion, μ Fe–V relationship has a good agreement with the previous reports. The μ Fe–S relationship showed the steep decrease of μ Fe around S∼ 0.6. In contrast to μ Fe–V relationship, μ Fe–S relationship does not match only from ours to previous studies but also among other reports. It implies the statistical number of the nearest-neighbor Fe–Fe bonds, i.e. S, cannot be an enough explanatory parameter. To clarify the structural origin of change in μ Fe, the short-range order (SRO) parameter inferred from the analysis of superlattice diffractions were introduced. They showed the clear difference for the films with high and low μ Fe. The results suggest that the transition from the long- to the SRO state plays the significant role on μ Fe.

Effects of removal of the axial methionine heme ligand on the binding of S. cerevisiae iso-1 cytochrome c to cardiolipin

The cleavage of the axial S(Met) – Fe bond in cytochrome c (cytc) upon binding to cardiolipin (CL), a glycerophospholipid of the inner mitochondrial membrane, is one of the key molecular changes that impart cytc with (lipo)peroxidase activity essential to its pro-apoptotic function. In this work, UV – VIS, CD, MCD and fluorescence spectroscopies were used to address the role of the Fe − M80 bond in controlling the cytc-CL interaction, by studying the binding of the Met80Ala (M80A) variant of S. cerevisiae iso-1 cytc (ycc) to CL liposomes in comparison with the wt protein [Paradisi et al. J. Biol. Inorg. Chem. 25 (2020) 467–487]. The results show that the integrity of the six-coordinate heme center along with the distal heme site containing the Met80 ligand is a not requisite for cytc binding to CL. Indeed, deletion of the Fe – S(Met80) bond has a little impact on the mechanism of ycc-CL interaction, although it results in an increased heme accessibility to solvent and a reduced structural stability of the protein. In particular, M80A features a slightly tighter binding to CL at low CL/cytc ratios compared to wt ycc, possibly due to the lift of some constraints to the insertion of the CL acyl chains into the protein hydrophobic core. M80A binding to CL maintains the dependence on the CL-to-cytc mixing scheme displayed by the wt species.

CO2‐Induced Strong Room‐Temperature Ferromagnetism in BiFeO3

AbstractWith humongous demand for data storage and processing, two‐dimensional (2D) ferromagnetic‐based materials, is emerged as the next‐generation nanoelectronic devices due to their low power consumption and optimal memory and processing capabilities. BiFeO3 as a single‐phase multiferromagnetic material is expected to find potential applications in electromagnetic devices. Herein, 2D room‐temperature ferromagnetic BiFeO3 is obtained with the help of supercritical carbon dioxide (SC CO2). The rhombic phase of BiFeO3 is converted to cubic with the creation of Ov and Fe2+ defects over the SC CO2 treatment, leading to significant ferromagnetic enhancement. More importantly, it is found that SC CO2 can destroy the cycloidal spin structure of BiFeO3 leading to an increase in the Fe─O─Fe bond angle, which generates stronger superexchange interactions. Ultimately, the saturation magnetization strength of BiFeO3 is increased by nearly 23 times. A new strategy is provided for ferromagnetic induction in 2D materials, which is favorable for promoting their practical applications on device architectures in the future.

Coal gasification slag-derived highly reactive silica for high modulus sodium silicate synthesis: Process and mechanism

Coal gasification slag (CGS) was used to synthesize highly reactive silica, which can be rapidly dissolved in dilute alkali solution at ambient temperature. High modulus sodium silicate was further synthesized by alkali dissolution at ambient temperature instead of the conventional high temperature melting method. During the acid activation process, the inert Si-O-M (M = Al, Ca, Fe) bonds are broken, resulting in the formation of Q3 and Q2 coordination structures with active Si-O-H bonds. The active Si-O-H bonds are further spontaneously condensed to generate highly reactive amorphous silica with a low Si-O-Si bond strength. Under the optimum reaction temperature of 25℃ and reaction time of 0.5 h, the leaching efficiency of Al, Ca and Fe are 86.20 %, 97.61 % and 97.83 % respectively, and the solubility of silica can reach 97.85 %. During the alkali dissolution of silica process, with the decrease of NaOH concentration and liquid–solid ratio, the breaking of Si-O-Si bridging oxygen bond and the formation of Si-O-Na non-bridging oxygen bond can be decreased, resulting in the direct dissociation of the Si-O groups into the liquid phase in the form of polysilicate, thus synthesizing high modulus sodium silicate. Under the optimum reaction temperature of 25℃ and reaction time of 0.5 h, the leaching efficiency of silica is 76.35 % and the modulus of sodium silicate can reach 3.28. The findings of this study provide valuable insights for enriching the theoretical basis of alkali solution-based silica dissolution and for improving the energy-intensive status of the silica industry.