Understanding the dehydrogenation mechanism over iron nanoparticles catalysts based on density functional theory

The conversion of chemical feedstock materials into high value-added products accompanied with dehydrogenation is of great value in the chemical industry.However,the catalytic dehydrogenation reaction is inhibited by a limited number of expensive noble metal catalysts and lacks understanding of dehydrogenation mechanism.Here,we report the use of heterogeneous non-noble metal iron nanoparticles(NPs) incorporated mesoporous nitrogen-doped carbon to investigate the dehydrogenation mechanism based on experiment observation and density functional theory(DFT) method.Fe NPs catalyst displays excellent performance in the dehydrogenation of 1,2,3,4-tetrahydroquinoline(THQ)with 100% selectivity and 100% conversion for 10-12 h at room temperature.The calculated adsorption energy implies that THQ prefers to adsorb on Fe NPs as compared with absence of Fe NPs.What is more,the energy barrier of transition state is relatively low,illustrating the dehydrogenation is feasible.This work provides an atomic scale mechanism guidance for the catalytic dehydrogenation reaction and points out the direction for the design of new catalysts.     

Catalytic properties of Fe-Cu-Al-montmorillonites in the oxidation of acid chrome dark blue azo dye

Interlayer cations in the sodium form of the aluminosilicate montmorillonite (Mt) have been exchanged by mixed, bulky, polynuclear hydroxo cations (Al: (Fe + Cu) = 10, Cu: Fe = 0–1, OH: (Fe + Cu + Al) = 2), and the product has been heat-treated to obtain Fe-, Fe-Al-, and Fe-Cu-Al-containing materials (Fe-Cu-Al-Mt). The chemical composition and textural characteristics of the materials depend on the Cu: Fe molar ratio. The catalytic properties of the materials in the oxidation of acid chrome dark blue (ACDB) azo dye with hydrogen peroxide have been investigated. The activity and stability of the Fe-Cu-Al-Mt systems are determined by the quantity of copper and iron atoms introduced into the structure of the material. As the iron ion content is increased, the specific catalytic activity of the system increases and the system becomes less resistant to the leaching of iron ions into the solution. Raising the copper content of the system above 0.07 wt % reduces its activity and stability. The effects of the catalyst content, pH of the solution being oxidized, and reactant ratio (H₂O₂: ACDB) on the reaction rate have been studied. The ACDB oxidation conditions have been optimized.     

Rapid freeze-quench 57Fe Mössbauer spectroscopy: monitoring changes of an iron-containing active site during a biochemical reaction

Nuclear gamma resonance spectroscopy, also known as M?ssbauer spectroscopy, is a technique that probes transitions between the nuclear ground state and a low-lying nuclear excited state. The nucleus most amenable to M?ssbauer spectroscopy is 57Fe, and 57Fe M?ssbauer spectroscopy provides detailed information about the chemical environment and electronic structure of iron. Iron is by far the most structurally and functionally diverse metal ion in biology, and 57Fe M?ssbauer spectroscopy has played an important role in the elucidation of its biochemistry. In this article, we give a brief introduction to the technique and then focus on two recent exciting developments pertaining to the application of 57Fe M?ssbauer spectroscopy in biochemistry. The first is the use of the rapid freeze-quench method in conjunction with M?ssbauer spectroscopy to monitor changes at the Fe site during a biochemical reaction. This method has allowed for trapping and subsequent detailed spectroscopic characterization of reactive intermediates and thus has provided unique insight into the reaction mechanisms of Fe-containing enzymes. We outline the methodology using two examples: (1) oxygen activation by the non-heme diiron enzymes and (2) oxygen activation by taurine:alpha-ketoglutarate dioxygenase (TauD). The second development concerns the calculation of M?ssbauer parameters using density functional theory (DFT) methods. By using the example of TauD, we show that comparison of experimental M?ssbauer parameters with those obtained from calculations on model systems can be used to provide insight into the structure of a reaction intermediate.     

Fe analysis by the ferrozine method: Adaptation to FIA towards in situ analysis in hydrothermal environment

The target of this study is the adaptation of the ferrozine method to flow injection analysis (FIA) to perform iron analysis in situ using an in situ chemical analyser in hydrothermal environments. The adaptation of the method to FIA was followed by its optimisation using an experimental design screening method. The goals of the optimisation steps were to decrease the detection limit and to increase the measuring range to cope with the constraints of in situ analysis. The method allows the determination of iron in the mixing zone of hydrothermal fluid, enriched in iron, and seawater. A single manifold gives the possibility to analyse either Fe(II) or ΣFe [Fe(II) + Fe(III)] in situ, or ΣFe in the lab on hydrothermal seawater samples. The measuring range of the method was increased to up to 2000 μM, which is coherent with the study of the chemical environment of communities associated with deep-sea hydrothermal activity. Finally, the method was applied in situ using the chemical analyser Alchimist during the ATOS cruise on hydrothermal vent fields on the Mid Atlantic Ridge.     

Fe-based phosphate nanostructures for supercapacitors

Fe-based phosphates with excellent physical and chemical features are potential electrode materials for supercapacitors.In this work,we successfully synthesized Fe-based phosphates with different dimensions,morphologies,and compositions by one-step hydrothermal method.Influence factors on the chemical composition and morphology of the as-prepared materials were explored and the energy storage performance of the as-prepared samples were tested under the traditional three electrode system.Two-dimensional(2 D) iron metaphosphate(Fe(PO_3)_3) showed the best electrochemical performance.For Fe(PO_3)_3 electrode mate rials,the layered structure can provide a larger specific surface area than the bulk structure,which is conducive to the diffusion and transport of electrolyte ions during charging-discha rging and further improve s the rate perfo rmance and cycle stability of supe rcapacito r.2 D Fe(PO_3)_3 and activated carbon were used as electrode materials to construct a 2 D Fe(PO_3)_3//AC supercapacitor.The supercapacitor showed high energy density,high power density,and excellent cycling stability,which indicates 2 D Fe(PO_3)_3 is a promising electrode material for supercapacitors.     

Hierarchical Hollow Nanoprisms Based on Ultrathin Ni‐Fe Layered Double Hydroxide Nanosheets with Enhanced Electrocatalytic Activity towards Oxygen Evolution

The oxygen evolution reaction (OER) is involved in various renewable energy systems, such as water‐splitting cells and metal–air batteries. Ni‐Fe layered double hydroxides (LDHs) have been reported as promising OER electrocatalysts in alkaline electrolytes. The rational design of advanced nanostructures for Ni‐Fe LDHs is highly desirable to optimize their electrocatalytic performance. Herein, we report a facile self‐templated strategy for the synthesis of novel hierarchical hollow nanoprisms composed of ultrathin Ni‐Fe LDH nanosheets. Tetragonal nanoprisms of nickel precursors were first synthesized as the self‐sacrificing template. Afterwards, these Ni precursors were consumed during the hydrolysis of iron(II) sulfate for the simultaneous growth of a layer of Ni‐Fe LDH nanosheets on the surface. The resultant Ni‐Fe LDH hollow prisms with large surface areas manifest high electrocatalytic activity towards the OER with low overpotential, small Tafel slope, and remarkable stability.     

Electrotransport in binary iron-based metal melts

The mobility of ions in binary iron-based liquid metal systems is calculated for the first time, based on studies on the specific resistance and self-diffusion coefficient in a wide range of concentrations. It is established that iron ions move toward the anode in Fe–V and Fe–Mo systems, and toward the cathode in Fe–W and Fe–Pt systems; i.e., there is inversion of electrotransport for iron ions. When the concentration of a component is reduced, the mobility of its ions grows in modulus.     

Multielemental analysis of metallurgical samples by thermal neutron activation

Instrumental neutron activation analysis (INAA) was applied to investigated a total of 16 samples of raw materials, intermediate and final products involved in metallurgical processes in Romanian Iron and Stell works Sidex Galatzy: iron ores and pellets from different regions of the world, cast iron, slag and steels. A series of chemical elements was determined in the analyzed samples: Al, As, Ce, Co, Cr, Fe, La, Mn, Na, Sc, Sm, V, W. A qualitative discussion regarding the passing of from elements with different chemical affinity for oxygen compared to that of iron, from the raw materials to slag or to finite products is presented.     

Synthesis and characterization of highly magnetized nanocrystalline Co(30)Fe(70) alloy by chemical reduction

Co(30)Fe(70) nanoparticles with mean particle size of about 8 nm were successfully synthesized by the chemical reduction of cobalt chloride and iron chloride with borohydride as a reducing agent in aqueous solution. The composition and size of the Co(30)Fe(70) nanoparticles were optimized by controlling the molar ratio of starting materials, reaction time, and dropping rate of aqueous reducing agent. As alloy powders prepared by chemical reduction tend to be amorphous in the as-synthesized state, the as-precipitated Co(30)Fe(70) nanoparticles were heat-treated to achieve crystallinity at the different temperatures for 1 h. The Co(30)Fe(70) nanocrystallite by chemical reduction shows excellent soft magnetic behavior, such as high permeability, negligible coercivity, and high saturation magnetization like that of Co(30)Fe(70) bulk.     

铁基双金属材料还原降解三溴甲烷的研究

本文制备了Cu/Fe和Pd/Fe两种铁基双金属材料,考察它们对溴仿(CHBr_3)的还原去除效果。结果表明,溴仿的还原去除效果都随双金属材料投加量的增加而增加;溶液中H~+浓度越高,越有利于还原反应的进行;溶解氧的存在会对还原去除反应产生抑制作用。双金属材料与溴仿的还原去除反应包括直接还原和间接还原两种途径。Pd和Cu通过与零价铁组成原电池结构加快了零价铁在水中的腐蚀速度,从而增强了零价铁对溴仿的直接还原去除效果。Pd与Cu相比,具有更高的氢过电位,氢气更容易在Pd的表面生成,而氢气也可以作为还原剂,取代溴仿分子中的溴原子,完成还原脱卤。因此,Pd/Fe双金属材料对溴仿的还原去除效果要好于Cu/Fe双金属材料。     

One-Step Preparation of Fe/N/C Single-Atom Catalysts Containing Fe−N4 Sites from an Iron Complex Precursor with 5,6,7,8-Tetraphenyl-1,12-Diazatriphenylene Ligands

Fe/N/C single-atom catalysts containing Fe−N_x sites prepared by pyrolysis are promising cathode materials for fuel cells and metal-air batteries due to their high oxygen reduction reaction (ORR) activities. We have developed iron complexes containing N2- or N3-chelating coordination structures with preorganized aromatic rings in a 1,12-diazatriphenylene framework tethering bromo substituents as precursors to precisely construct Fe−N₄ sites in an Fe/N/C catalyst. One-step pyrolysis of the iron complex with carbon black forms atomically dispersed Fe−N₄ sites without iron aggregates. X-ray absorption spectroscopy (XAS) and electrochemical measurements revealed that the iron complex with N3-coordination is more effectively converted to Fe−N₄ sites catalyzing ORR with a TOF value of 0.21 e site⁻¹ s⁻¹ at 0.8 V vs. RHE. This indicates that the formation of Fe−N₄ sites is controlled by precise tuning of the chemical structure of the iron complex precursor.     

Chiral recognition applications of molecularly imprinted polymers: a critical review

Molecular imprinting technology offers the unique opportunity to tailor chiral stationary phases with predefined chiral recognition properties by employing the enantiomers of interest as binding-site-forming templates. Added advantages, such as ease of preparation, chemical robustness, low-cost production, and the possibility of shaping molecularly imprinted polymers (MIPs) in various self-supporting formats, render them attractive materials for a broad range of chiral recognition applications. In this review a critical overview on recent developments in the field of MIP-based chiral recognition applications is given, focusing on separation techniques and molecular sensing. Inherent limitations associated with the use of enantioselective MIP materials in high-performance separation techniques are outlined, including binding site heterogeneity and slow mass transfer characteristics. The prospects of MIP materials as versatile recognition elements for the design of enantioselective sensor systems are highlighted.     

On-Surface Synthesis of Iron Phthalocyanine Using Metal-Organic Coordination Templates

On-surface synthesis provides a convenient route to many kinds of conjugated molecular nanostructures, but it has remained challenging to precisely control the reaction pathway for using multicomponent precursors. Herein, we demonstrate a two-step strategy to synthesize iron phthalocyanine (FePc) molecules using metal-organic coordination for templating by using high-resolution scanning tunnelling microscopy and non-contact atomic force microscopy. In a first step, 1,2,4,5-tetracyanobenzene (TCNB) precursors and Fe atoms self-assembly into Fe(TCNB)₄ coordination complexes on a clean Au(111) surface. The Fe(TCNB)₄ complexes further undergo cyclic tetramerization upon thermal annealing, forming single FePc molecules. We expect that our demonstrated synthetic strategy may shed light on the design and synthesis of two-dimensional extended conjugated systems.     

Iron promotion of V‐HMS mesoporous catalysts for ultra‐deep oxidative desulfurization

Bimetallic Fe‐V‐HMS (HMS, hexagonal mesoporous silica) catalysts with various molar ratios of iron to vanadium were synthesized using a co‐synthesis method, and investigated for oxidative desulfurization of dibenzothiophene (DBT) using tert‐butyl hydroperoxide as an oxidant. The catalysts were characterized using X‐ray diffraction, temperature‐programmed desorption of ammonia, Fourier transform infrared spectroscopy and N₂ physical adsorption–desorption techniques. The Fe‐V‐HMS catalyst with a 2:1 molar ratio of iron to vanadium exhibited the highest total acidity and the highest catalytic activity. DBT was almost completely oxidized to dibenzothiophenesulfone, a species with a higher polarity that could be subsequently adsorbed on the Fe‐V‐HMS, and therefore the Fe‐V‐HMS acts as both a catalyst and an adsorbent simultaneously. The desulfurization rate was 98.1%. A pseudo‐first‐order model was fitted to the experimental data, and the activation energy was found to be 38.79 kJ mol^?1. The encouraging performance of Fe‐V‐HMS offers the prospect of the design of a one‐pot oxidative desulfurization process without needing extraction of sulfones from fuel oil with a chemical solvent.     

Nucleic Acid Based Logical Systems

Researchers increasingly visualize a significant role for artificial biochemical logical systems in biological engineering, much like digital logic circuits in electrical engineering. Those logical systems could be utilized as a type of servomechanism to control nanodevices in vitro, monitor chemical reactions in situ, or regulate gene expression in vivo. Nucleic acids (NA), as carriers of genetic information with well‐regulated and predictable structures, are promising materials for the design and engineering of biochemical circuits. A number of logical devices based on nucleic acids (NA) have been designed to handle various processes for technological or biotechnological purposes. This article focuses on the most recent and important developments in NA‐based logical devices and their evolution from in vitro, through cellular, even towards in vivo biological applications.     

Bioinspired Transition-Metal Complexes as Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is one of the most important reactions in life processes and energy conversion systems. To alleviate global warming and the energy crisis, the development of high-performance electrocatalysts for the ORR for application in energy conversion and storage devices such as metal–air batteries and fuel cells is highly desirable. Inspired by the biological oxygen activation/reduction process associated with heme- and multicopper-containing metalloenzymes, iron and copper-based transition-metal complexes have been extensively explored as ORR electrocatalysts. Herein, an outline into recent progress on non-precious-metal electrocatalysts for the ORR is provided; these electrocatalysts do not require pyrolysis treatment, which is regarded as desirable from the viewpoint of bioinspired molecular catalyst design, focusing on iron/cobalt macrocycles (porphyrins, phthalocyanines, and corroles) and copper complexes in which the ORR activity is tuned by ligand variation/substitution, the method of catalyst immobilization, and the underlying supporting materials. Current challenges and exciting imminent developments in bioinspired ORR electrocatalysts are summarized and proposed.     

Design of molecular magnets

The conventional magnetic materials used in present-day technology, such as Fe, Fe₂O₃, Cr₂O₃, SmCo₅, Nd₂Fe₁₄B, etc. are all atom-based, whose synthesis requires high-temperature routes. Employing ambient-temperature synthetic organic chemistry, it has become possible to engineer a bulk molecular material with long-range magnetic order, primarily due to the weak nature of intermolecular interactions in it. Typical synthetic approach to design molecule-based magnets consists of choosing molecular precursors, each bearing an unpaired spin, and assembling them in such a way that there is no compensation of spins at the scale of the crystal lattice. Magnetism being a co-operative effect, the spin-spin interaction must extend to all the three dimensions, either through space or through bonds. Specific occurrence of ‘spin delocalisation’ and ‘spin polarisation’ in molecular lattices is helpful in bringing about ferromagnetic interaction by facilitating necessary intermolecular exchange interactions. Since the first successful synthesis of molecular magnets in 1986, a large variety of them have been synthesized, which can be classified on the basis of the chemical nature of the magnetic units involved: organic systems, metal-based systems, hetero-bimetallic assemblies, or mixed organic-inorganic systems. The design of molecular magnets has also opened the doors for the unique possibility of designing polyfunctional molecular materials, such as magnets exhibiting second-order optical nonlinearity, liquid crystalline magnets, or chiral magnets. Solubility of molecular magnets, their low density and biocompatibility are attractive features. Being weakly colored, unlike the opaque classic magnets, possibilities of photomagnetic switching can be envisaged. Persistent efforts continue to design the ever-elusive polymer magnets for applications in industry. While providing a brief overview of the field of molecular magnetism, we highlight some recent developments, with emphasis on a few studies from the author's own lab.     

铁配合物的环境光化学及其参与的环境化学过程

铁是地壳中含量最为丰富的金属元素之一,而自然界中存在的绝大多数溶解性铁都是以有机络合形式存在的。环境中的铁配合物在光照下会发生直接光解和次级的(光)化学反应过程,生成还原性的Fe(Ⅱ)和有机自由基以及衍生的活性氧物种。铁配合物的环境光化学反应将深刻影响着氧自由基的生成与衰减、有机物降解和其他元素的环境化学循环过程,因此,成为近年来国际环境科学领域的研究热点。本文介绍了铁配合物光还原反应的类型和原理,分析了Fe(Ⅱ)(光)化学氧化的可能机理和影响因素,并对国内外关于铁参与的环境化学过程所开展的研究进行了评述。在此基础上,通过分析目前研究中所存在的问题,对今后的研究方向和趋势作了展望。     

Correlating Fe source with Fe-N-C active site construction:Guidance for rational design of high-performance ORR catalyst

Pyrolyzed Fe-N_X/C materials derived from Fe-doped ZIF-8 are recently emerged as promising alternatives to noble metal platinum-based catalysts towards oxygen reduction reaction(ORR) and elucidating the dependacne of Fe source on the active site structure and final ORR performance is highly desirbale for further development of these materials. Here, we designed and synthesized a series of Fe-N-C catalysts using ZIF-8 and various iron salts(Fe(acac)_3, FeCl_3, Fe(NO_3)_3) as precusors. We found that the iron precursors,mainly the molecular size, hydrolysis extent, do play a major role in determining the final morphology of Fe, namely forming the Fe-Nx coordination or Fe_3C nanoparticles, as well as the site density, therefore,significantly affecting the ORR activity. Among the three iron sources, Fe(acac)_3 is most advantageous to the preferential formation of single-atom Fe-Nx active sites and the derived catalyst demonstrated best ORR performance.