Study of formation and thermal stability of the Fe/ZnO(000‐1) interface

Formation and thermal stability of the Fe/ZnO(000‐1) interface have been studied by means of X‐ray photoelectron spectroscopy and low energy electron diffraction. The results indicated a pseudo 2D growth mode for iron on ZnO. In addition, it could be shown that under ultra high vacuum conditions deposited Fe⁰ on a ZnO(000‐1) single crystal was partially oxidized by a small fraction of residual ? OH‐groups and ZnO to FeO. A strong temperature dependence of the interface reactivity was found upon annealing at temperatures up to 600 °C. Starting from 200 °C iron was first oxidized to bivalent iron oxide. After complete oxidation of Fe⁰ to Fe²⁺ at 375 °C, Fe²⁺ reacted to Fe³⁺. Above temperatures of 500 °C the deposited metallic iron was completely oxidized to trivalent iron. Further experiments with FeO on ZnO showed the oxidation state and the oxide film thickness of the deposited iron to be mainly dependent on the annealing temperature. Copyright © 2008 John Wiley & Sons, Ltd.     

Silver-reductor method for determination of iron in iron ores and iron-ore sinters

A new technique for the quick dissolution of iron ore, magnetite and sinter products has been developed. The sample is dissolved with thioglycollic acid and hydrochloric acid, the excess of thioglycollic acid is oxidized, and the iron is reduced in the silver reductor.     

Structures and magnetic and electronic properties of the O2-adsorbed Fe2N clusters

Structural Chemistry - The surface of iron nitrides prefers to be oxidized in the air, which reduces the cycling stability of the supercapacitors. The configurations and electronic and magnetic...     

Formation of pure hydrogen from methane

The methods for production of pure hydrogen from methane are summarized. One method is methane decomposition to hydrogen and carbon nanofibers. Ni-based catalysts with high activity and long life for the methane decomposition were developed. The other method is based on the redox of iron oxides, i.e., Fe₃O₄ is reduced with methane to iron metals and, subsequently, iron metals are oxidized with water vapor to form hydrogen. Iron oxide mediators that could be reduced with methane and subsequently be oxidized with water vapor at low temperatures were designed.     

Formation of pure hydrogen from methane

The methods for production of pure hydrogen from methane are summarized. One method is methane decomposition to hydrogen and carbon nanofibers. Ni-based catalysts with high activity and long life for the methane decomposition were developed. The other method is based on the redox of iron oxides, i.e., Fe₃O₄ is reduced with methane to iron metals and, subsequently, iron metals are oxidized with water vapor to form hydrogen. Iron oxide mediators that could be reduced with methane and subsequently be oxidized with water vapor at low temperatures were designed.     

Ozonocatalytic decomposition of glyoxal and glyoxylic and formic acids in the presence of iron(III) ions

Rate constants of reactions of ozone with glyoxal, glyoxylic and formic acid in aqueous solutions at pH 1.5 were determined. It was shown that iron(III) in the form of ions accelerates oxidation of glyoxal and glyoxylic acid, but does not influence reaction between ozone and formic acid. It was established that the catalyst acts effectively if its concentration is comparable to the concentration of the oxidized substrate, the optimal stoichiometric ratio (Fe³⁺/substrate) being close to 1/3. The catalytic reaction mechanism was studied using a competitive chelate ligand, oxalic acid. We concluded that the catalytic activity of iron(III) in the investigated reaction was due to its ability to form chelate complexes in which the substrate was more easily oxidized by molecular ozone.     

镧系元素光化学 Ⅳ 铁和铈对光还原分离铕的影响

本文在水溶液中以1:1HCOOH～HCOONa做自由基清除剂,Na_2SO_4做光还原产物Eu~(2+)沉淀剂,研究了杂质铁和含量变化对光还原分离铕的影响,并用紫外光谱证明了体系中是光反应生成的Fe和Ce~(4+)对发生氧化,致使Eu~(2+)光还原生成Eu~(2+)速度减慢,铕的收率下降。     

乙烷在金属铁表面还原NO的实验研究

温度300~1 100 ℃时,由程序控温电加热水平陶瓷管反应器在N₂气氛和模拟气氛下,对乙烷在金属铁表面还原NO的特性进行了实验研究。结果表明,乙烷在金属铁表面能够高效地还原NO。在N₂气氛中,温度高于900 ℃时,乙烷在金属铁表面的脱硝效率超过95%。在模拟烟气条件下,当温度超过900 ℃,且过量空气系数小于1.0时,乙烷在金属铁表面还原NO的效率能够达到90%以上。相同条件下,乙烷在金属铁表面脱硝效率高于甲烷的脱硝效率。SO₂对乙烷在金属铁表面还原NO的效率影响可以忽略。对反应后的铁样品的组分进行了XRD表征,在此基础上对反应机理进行了分析。结果表明,在模拟烟气条件下NO的还原通过乙烷的再燃脱硝和金属铁直接还原两个机理完成。金属铁直接还原NO时生成的氧化铁则被乙烷还原为金属铁,从而使得金属铁能够持续对NO进行直接还原。乙烷再燃还原NO的中间产物HCN被氧化铁氧化为N₂,同时氧化铁也被HCN还原为金属铁。这一过程增强了NO的持续还原反应,同时避免了在燃尽时HCN二次氧化重新生成NO,从而保证了较高的NO还原效率。     

壳聚糖稳定纳米铁的制备及其对地表水中Cr(Ⅵ)的去除性能

以可生物降解材料壳聚糖为稳定剂, 制备了平均粒径为 82.4 nm的纳米零价铁颗粒. 热重分析表明, 经壳聚糖改性后, 纳米铁在340 ℃以下具有很好的热稳定性. 批试验结果表明, 壳聚糖稳定纳米铁对水体中Cr(Ⅵ)有很强的去除能力, 在空气中放置60 d后, 壳聚糖稳定纳米铁仍具有较高的活性. 壳聚糖分子中的氨基和羟基可与Fe(Ⅲ)形成稳定的螯合物, 阻止Cr(Ⅲ)和Fe(Ⅲ)共沉淀的形成, 从而促进零价铁的腐蚀和Cr(Ⅵ)的还原去除.     

Evidence for the role of myoglobin in facilitating oxygen transport

Cyclic voltammetric studies of the heterogeneous electron-transfer reactions of myoglobin under aerobic and anaerobic conditions are reported. Evidence for a role of myoglobin that has not been previously measured directly, namely, facilitation of oxygen transport, is presented. It is suggested that one molecule of oxygen can be contained within the structure of the oxidized form of myoglobin, but is not co-ordinated to the heme iron. Reduced myoglobin binds one molecule of oxygen to the heme iron but no reports have been found that suggest that the oxidized form of myoglobin binds to, or contains a molecule of, oxygen.     

Electrochemical and Spectral Characterization of Iron Corroles in High and Low Oxidation States: First Structural Characterization of an Iron(IV) Tetrapyrrole pi Cation Radical

The electrochemistry and spectroscopic properties of three iron corroles were examined in benzonitrile, dichloromethane, and pyridine containing 0.1 M tetra-n-butylammonium perchlorate or tetra-n-ethylammonium hexafluorophosphate as supporting electrolyte. The investigated compounds are represented as (OEC)Fe(IV)(C(6)H(5)), (OEC)Fe(IV)Cl, and (OEC)Fe(III)(py), where OEC is the trianion of 2,3,7,8,12,13,17,18-octaethylcorrole. Each iron(IV) corrole undergoes two one-electron reductions and two or three one-electron oxidations depending upon the solvent. Under the same solution conditions, the iron(III) corrole undergoes a single one-electron reduction and one or two one-electron oxidations. Each singly oxidized and singly reduced product was characterized by UV-vis and/or EPR spectroscopy. The data indicate a conversion of (OEC)Fe(IV)(C(6)H(5)) and (OEC)Fe(IV)Cl to their iron(III) forms upon a one-electron reduction and to iron(IV) corrole pi cation radicals upon a one-electron oxidation. The metal center in [(OEC)Fe(III)(C(6)H(5))](-) is low spin (S = (1)/(2)) as compared to electrogenerated [(OEC)Fe(III)Cl](-), which contains an intermediate-spin (S = (3)/(2)) iron(III). (OEC)Fe(III)(py) also contains an intermediate-spin-state iron(III) and, unlike previously characterized (OEC)Fe(III)(NO), is converted to an iron(IV) corrole upon oxidation rather than to an iron(III) pi cation radical. Singly oxidized [(OEC)Fe(IV)(C(6)H(5))](*)(+) is the first iron(IV) tetrapyrrole pi cation radical to be isolated and was structurally characterized as a perchlorate salt. It crystallizes in the triclinic space group P&onemacr; with a = 10.783(3) ?, b = 13.826(3) ?, c = 14.151(3) ?, alpha = 78.95(2) degrees, beta = 89.59(2) degrees, and gamma = 72.98(2) degrees at 293 K with Z = 2. Refinement of 8400 reflections and 670 parameters against F(o)(2) yields R1 = 0.0864 and wR2 = 0.2293. The complex contains a five-coordinated iron with average Fe-N bond lengths of 1.871(3) ?. The formulation of the electron distribution in this compound was confirmed by M?ssbauer, X-ray crystallographic, and magnetic susceptibility data as well as by EPR spectroscopy, which gives evidence for strong antiferromagnetic coupling between the iron(IV) center and the singly oxidized corrole macrocycle.     

Determination of Active Metal in Ultradispersed Iron Powders and TG Study of Their Oxidation

Two oxidation stages of electrolytic ultradispersed iron powder at the temperature range of 90–450°C have been stated. The contribution of increasing mass and evolving heat at the first oxidation stage due to changing Fe⁰ into Fe₂O₃ in the total oxidation effect is predominant. The thermal method of active metal determination in electrolytic iron powders has been developed. The coarse-grained reduced iron powder was not oxidized completely just to 900°C because of local sintering of big iron particles as a result of evolving heat at oxidation of high-dispersed iron particles. This revised version was published online in August 2006 with corrections to the Cover Date.     

Multielectron redox chemistry of iron porphyrinogens

Iron octamethylporphyrinogens were prepared and structurally characterized in three different oxidation states in the absence of axial ligands and with sodium or tetrafluoroborate as the only counterions. Under these conditions, the iron- and ligand-based redox chemistry of iron porphyrinogens can be defined. The iron center is easily oxidized by a single electron (E(1/2) = -0.57 V vs NHE in CH(3)CN) when confined within the fully reduced macrocycle. The porphyrinogen ligand also undergoes oxidation but in a single four-electron step (E(p) = +0.77 V vs NHE in CH(3)CN); one of the ligand-based electrons is intercepted for the reduction of Fe(III) to Fe(II) to result in an overall three-electron oxidation process. The oxidation equivalents in the macrocycle are stored in C(alpha)-C(alpha) bonds of spirocyclopropane rings, formed between adjacent pyrroles. EPR, magnetic and Mossbauer measurements, and DFT computations of the redox states of the iron porphyrinogens reveal that the reduced ligand gives rise to iron in intermediate spin states, whereas the fully oxidized ligand possesses a weaker sigma-donor framework, giving rise to high-spin iron. Taken together, the results reported herein establish a metal-macrocycle cooperativity that engenders a multielectron chemistry for iron porphyrinogens that is unavailable to heme cofactors.     

A radioactive tracer and radiation study of the stability of ferric and ferrous ions and ascorbic acid

A preliminary liquid-liquid extraction study of ferric and ferrous ions has been undertaken using the radioactive tracer technique with⁵⁹Fe as an indicator of iron. Various solvents were studied and suitable media and solvents were selected for the separation of the two oxidation states of iron. Such separation was used to study the effect of ascorbic acid and other reducing agents on the reduction of ferric ions. The oxidation of ferrous ions to the ferric state under the effect of gamma radiation from⁶⁰Co has also been investigated in the absence and presence of ascorbic acid, using spectrophotometry. In addition, a calculation of the amount of iron oxidized by gamma radiation is given with a discussion of its mechanism and possible effects on the metabolism of iron in the human body.     

金属铁与丙烯共同还原NO的特性与机理

研究了丙烯在金属铁作用下还原NO的特性。采用陶瓷管流动反应器在300-1 100℃研究了不同条件下的NO还原效率,考察了SO_2的影响,采用XRD、SEM和EDS分析了反应后金属铁表面的组分和微观结构特征。结果表明,丙烯在金属铁作用下具有良好的NO还原效果。在N_2气氛,温度超过800℃后,金属铁作用下丙烯还原NO的效率达到了95%以上。在模拟烟气、富燃料条件下,温度高于900℃时,丙烯与金属铁还原NO的效率超过了90%。SO_2对丙烯在金属铁作用下还原NO的效率影响很小。机理分析表明,当丙烯与金属铁共同还原NO时,一方面,NO被金属铁直接还原,同时丙烯还原氧化铁为金属铁;另一方面,丙烯通过再燃机理还原NO,同时再燃中间产物被氧化铁氧化为N_2。     

In situ chemical oxidation of aniline by persulfate with iron(Ⅱ) activation at ambient temperature

<正>The kinetics of aniline degradation by persulfate processes with iron(Ⅱ) activation at ambient temperature was investigated in this study.With iron(Ⅱ) as initiator,the oxidation reactions were found to follow a biphasic rate phenomenon:a rapid transformation followed by a slow but sustained oxidation process.In the first 30 s,the reaction mainly relies on the persulfate-Fe~(2+) reaction in which aniline is oxidized rapidly.After 30 s,the aniline was still oxidized but the rate of reaction tended to be slower and the rates were clearly linear-proportional.After the initial fast oxidation,the reactions appeared to follow a pseudo-first-order model.     

The characterization of iron surfaces

The extensive literature data on the adsorptive properties and reactivity of iron single crystal surfaces, films, and supported catalysts is reviewed. The intent of this paper is (i) to narrow the present gap between the surface chemistry discipline and catalysis research, and (ii) to gain a detailed insight into common catalyst characterization procedures.The interaction of oxygen, hydrogen, carbon monoxide, and nitrogen with the single crystal surfaces (110), (100), and (111) as well as with film specimens is dealt with. In addition to the adsorptive properties of well-defined iron oxide specimens also the reactivity of oxidized single crystal substrates towards hydrogenation is treated. Comprehension of both the adsorptive properties and the reactivity of metallic as well as of oxidized iron surfaces is required to understand what molecular phenomena proceed during a chemisorption experiment on a catalyst sample. Volumetric gas adsorption, temperature-programmed desorption, Mössbauer spectroscopy, and infrared spectroscopy experiments are discussed in relation to the above fundamental studies.The unfathomed discrepancy between the hydrogen adsorption features of single crystals and high-disperse supported iron catalysts can be appreciated from surface science constituents. The presence of oxygen at the metal-UHV interface of small metallic iron particles is made plausible. An alternative explanation for the magnetic anisotropy of magnesia- and silica-supported iron particles is advanced (exchange anisotropy).     

Synthesis and properties of sol-gel submicron silica powders doped with partly oxidized iron particles

Magnetic powders based on metallic iron crystallites encapsulated in submicron-sized spherical silica particles have been obtained and investigated. The metallic iron clusters have been produced by the exploding wire method. The silica shells have been prepared via the modified sol-gel Stöber method and the metallic particles have been entrapped by occlusion during the silica powder formation. The entrapped iron particles are partially oxidized due to the nature of the synthetic methods employed. The obtained hybrid materials have been investigated by electron microscopy, X-ray diffraction, magnetic and ζ-potential techniques. Such materials can be employed in such applications as e.g. magnetically-controlled drug vectors or electromagnetic field-shielding.     

A Non-Heme Iron(III) Complex with Porphyrin-like Properties That Catalyzes Asymmetric Epoxidation

In this report, we describe an iron(III) complex containing a carbazole-based tridentate ligand that catalyzes highly enantioselective asymmetric epoxidation of (E)-alkenes at room temperature. The non-heme iron(III) complex has a five-coordinated trigonal-bipyramidal structure, and its two-electron oxidized state has the similar electronic structure as that of iron porphyrins.     

Iron(III) and iron(IV) corroles: synthesis,spectroscopy, structures,and no indications for corrole radicals

A delicate control of reaction conditions allows the isolation of several distinctively different iron complexes of tris(pentafluorophenyl)- and tris(2,6-dichlorophenyl)corrole. As long as coordinating ligands are present, the iron(III) complexes are stable in solution. Otherwise they are aerobically oxidized to either mononuclear chloroiron(IV) or dinuclear (mu-oxo)iron(IV) complexes, in acidic and basic solutions, respectively (the latter holds only for tris(pentafluorophenyl)corrole). When treated with NaNO(2), the mononuclear chloroiron(IV) corroles are efficiently converted into diamagnetic iron nitrosyl complexes. The low- and intermediate-spin iron(III), iron nitrosyl, and chloroiron(IV) corroles were fully characterized by a combination of spectroscopic methods and X-ray crystallography. There was no indication for an open-shell corrole in any of the complexes.