Electrodeposition of Defect-Rich Ternary NiCoFe Layered Double Hydroxides: Fine Modulation of Co3+ for Highly Efficient Oxygen Evolution Reaction

The low-cost, high-abundance and durable layered double hydroxides (LDHs) have been considered as promising electrocatalysts for oxygen evolution reaction (OER). However, the easy agglomeration of lamellar LDHs in the aqueous phase limits their practical applications. Herein, a series of ternary NiCoFe LDHs were successfully fabricated on nickel foam (NF) via a simple electrodeposition method. The as-prepared Ni(Co_0.5Fe_0.5)/NF displayed an unique nanoarray structural feature. It showed an OER overpotential of 209 mV at a current density of 10 mA cm⁻² in alkaline solution, which was superior to most systems reported so far. As evidenced by the XPS and XAFS results, such excellent performance of Ni(Co_0.5Fe_0.5)/NF was attributed to the higher Co³⁺/Co²⁺ ratio and more defects exposed, comparing with Ni(Co_0.5Fe_0.5)-bulk and Ni(Co_0.5Fe_0.5)-mono LDHs prepared by conventional coprecipitation method. Furthermore, the ratio of Co to Fe could significantly tune the Co electronic structure of Ni(Co_xFe_1-x)/NF composites (x=0.25, 0.50 and 0.75) and affect the electrocatalytic activity for OER, in which Ni(Co_0.5Fe_0.5)/NF showed the lowest energy barrier for OER rate-determining step (from O* to OOH*). This work proposes a facile method to develop high-efficiency OER electrocatalysts.     

Developing Intense Blue and Magenta Colors in α‐LiZnBO3: The Role of 3d‐Metal Substitution and Coordination

We describe the synthesis, crystal structures, and optical absorption spectra/colors of 3d‐transition‐metal‐substituted α‐LiZnBO₃ derivatives: α‐LiZn_1?xM^II_xBO₃ (M^II=Co^II (0<x<0.50), Ni^II (0<x≤0.05), Cu^II (0<x≤0.10)) and α‐Li_1+xZn_1?2xM^III_xBO₃ (M^III=Mn^III (0<x≤0.10), Fe^III (0<x≤0.25)). The crystal structure of the host α‐LiZnBO₃, which is both disordered and distorted with respect to Li and Zn occupancies and coordination geometries, is largely retained in the derivatives, which gives rise to unique colors (blue for Co^II, magenta for Ni^II, violet for Cu^II) that could be of significance for the development of new, inexpensive, and environmentally friendly pigment materials, particularly in the case of the blue pigments. Accordingly, this work identifies distorted tetrahedral MO₄ (M=Co, Ni, Cu) structural units, with a long M?O bond that results in trigonal bipyramidal geometry, as new chromophores for blue, magenta, and violet colors in a α‐LiZnBO₃ host. From the L*a*b* color coordinates, we found that Co‐substituted compounds have an intense blue color that is stronger than that of CoAl₂O₄ and YIn_0.90Mn_0.10O₃. The near‐infrared (NIR) reflectance spectral studies indicate that these compounds exhibit a moderate IR reflectivity that could be significant for applications as “cool pigments”.     

Chemoselective Hydrogenation of Nitroaromatics at the Nanoscale Iron(III)–OH–Platinum Interface

Catalytic hydrogenation of nitroaromatics is an environment‐benign strategy to produce industrially important aniline intermediates. Herein, we report that Fe(OH)_x deposition on Pt nanocrystals to give Fe(OH)_x/Pt, enables the selective hydrogenation of nitro groups into amino groups without hydrogenating other functional groups on the aromatic ring. The unique catalytic behavior is identified to be associated with the Fe^III‐OH‐Pt interfaces. While H₂ activation occurs on exposed Pt atoms to ensure the high activity, the high selectivity towards the production of substituted aniline originates from the Fe^III‐OH‐Pt interfaces. In situ IR, X‐ray photoelectron spectroscopy (XPS), and isotope effect studies reveal that the Fe³⁺/Fe²⁺ redox couple facilitates the hydrodeoxygenation of the ‐NO₂ group during hydrogenation catalysis. Benefitting from Fe^III‐OH‐Pt interfaces, the Fe(OH)_x/Pt catalysts exhibit high catalytic performance towards a broad range of substituted nitroarenes.     

Modulating the Electronic Structure of Porous Nanocubes Derived from Trimetallic Metal–Organic Frameworks to Boost Oxygen Evolution Reaction Performance

The preparation of noble metal‐free catalysts for water splitting is the key to low‐cost, sustainable hydrogen generation. Herein, through a pyrolysis‐oxidation process, we prepared a series of Co‐Fe‐Ni trimetallic oxidized carbon nanocubes (Co_1‐XFe_XNi‐OCNC) with a continuously changeable Co/Fe ratio (X=0, 0.1, 0.2, 0.5, 0.8, 0.9, 1). The Co_1‐XFe_XNi‐OCNC shows a volcano‐type oxygen evolution reaction (OER) activity. The optimized Co_0.1Fe_0.9Ni‐OCNC achieves a low overpotential of 268 mV at 10 mA cm^?2 with a very low Tafel slope of 48 mV dec^?1 in 1 m KOH. At the same time, the stability of the Co_0.1Fe_0.9Ni‐OCNC is also outstanding; after 1000 CV cycles, the LSV plot is almost coincident. Moreover, the potential remains almost of the same value at 10 mA cm^?2 after 12 h in comparison to the initial value. The excellent electrocatalytic properties can be attributed to the synergistic cooperation between each component. Therefore, the Co_0.1Fe_0.9Ni‐OCNC is a promising candidate instead of precious metal‐based electrocatalysts for OER.     

Chemoselective Hydrogenation of Nitroaromatics at the Nanoscale Iron(III)–OH–Platinum Interface

Catalytic hydrogenation of nitroaromatics is an environment-benign strategy to produce industrially important aniline intermediates. Herein, we report that Fe(OH)_x deposition on Pt nanocrystals to give Fe(OH)_x/Pt, enables the selective hydrogenation of nitro groups into amino groups without hydrogenating other functional groups on the aromatic ring. The unique catalytic behavior is identified to be associated with the Fe^III-OH-Pt interfaces. While H₂ activation occurs on exposed Pt atoms to ensure the high activity, the high selectivity towards the production of substituted aniline originates from the Fe^III-OH-Pt interfaces. In situ IR, X-ray photoelectron spectroscopy (XPS), and isotope effect studies reveal that the Fe³⁺/Fe²⁺ redox couple facilitates the hydrodeoxygenation of the -NO₂ group during hydrogenation catalysis. Benefitting from Fe^III-OH-Pt interfaces, the Fe(OH)_x/Pt catalysts exhibit high catalytic performance towards a broad range of substituted nitroarenes.     

CoOOH Nanosheets with High Mass Activity for Water Oxidation

Endowing transition‐metal oxide electrocatalysts with high water oxidation activity is greatly desired for production of clean and sustainable chemical fuels. Here, we present an atomically thin cobalt oxyhydroxide (γ‐CoOOH) nanosheet as an efficient electrocatalyst for water oxidation. The 1.4 nm thick γ‐CoOOH nanosheet electrocatalyst can effectively oxidize water with extraordinarily large mass activities of 66.6 A g^?1, 20 times higher than that of γ‐CoOOH bulk and 2.4 times higher than that of the benchmarking IrO₂ electrocatalyst. Experimental characterizations and first‐principles calculations provide solid evidence to the half‐metallic nature of the as‐prepared nanosheets with local structure distortion of the surface CoO_6?x octahedron. This greatly enhances the electrophilicity of H₂O and facilitates the interfacial electron transfer between Co ions and adsorbed ‐OOH species to form O₂, resulting in the high electrocatalytic activity of layered CoOOH for water oxidation.     

A study on the thermal decomposition of iron-cobalt mixed hydroxides

Thermal decomposition of pure Fe(OH)₃ and mixed with Co(OH)₂ were studied using TG, DTA, kinetics of isothermal decomposition and electrical conductivity measurements. The thermal products were characterized by X-ray diffraction and IR spectroscopy. The TG and DTA analysis revealed the presence of Co²⁺ retards the decomposition of ferric hydroxide and the formation of -Fe₂O₃. The kinetics of decomposition showed that the mixed samples need higher energy to achieve thermolysis. The investigation of thermal products of mixed samples indicated the formation of cobalt ferrite on addition ofx=1 or 1.5 cobalt hydroxide. The electrical conductivity accompanying the thermal decomposition decreases in presence of low ratio of Co²⁺ (x=0.2) via the consumption of holes created during thermal analysis. The continuous increase in values on increasing of Co²⁺ concentration corresponded to the electron hopping between Fe²⁺ and Co³⁺.

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Zusammenfassung Mittels TG, DTA und der Kinetik von Messungen der isothermen Zersetzung und der elektrischen Leitfähigkeit wurde die Zersetzung von Fe(OH)₃ in reinem Zustand und vermengt mit Co(OH)₂ untersucht. Die thermischen Produkte wurden mittels Röntgendiffraktion und IR-Spektroskopie charakterisiert. TG und DTA zeigen, daß die Zersetzung von Eisen(III)-hydroxid und die Bildung von -Fe₂O₃ durch Gegenwart von Co²⁺ verzögert wird. Die Zersetzungskinetik zeigt, daß die Mischproben mehr Energie für die Thermolyse benötigen. Die Untersuchung der thermischen Produkte zeigt die Bildung von Cobaltferrit bei Zusatz vonx=1 oder 1,5 Cobalthydroxid. Die elektrische Leitfähigkeit nimmt bei der thermischen Zersetzung in Gegenwart von niedrigen Co²⁺-Konzentrationen (x=0.2) durch Verbrauch der bei der Thermoanalyse geschaffenen Löcher ab. Das monotone Ansteigen der -Werte bei steigender Co²⁺-Konzentration stimmt mit dem Überspringen von Elektronen zwischen Fe²⁺ und Co³⁺ überein.

     

In situ electrochemical dehydrogenation of ultrathin Co(OH)2 nanosheets for enhanced hydrogen evolution

Transition metal hydroxides/oxyhydroxides have recently emerged as highly active electrocatalysts for oxygen evolution reaction in alkaline water electrolysis, while have not yet been widely investigated for hydrogen evolution electrocatalysts owing to their unfavorable H*-adsorption, making it difficult to construct an overall-water-splitting cell for hydrogen production. In this work, we proposed a straightforward and effective approach to develop an efficient in-plane heterostructured CoOOH/Co(OH)₂ catalyst via in-situ electrochemical dehydrogenation method, in which the dehydrogenated –CoOOH and Co(OH)₂ at the surface synergistically boost the hydrogen evolution reaction (HER) kinetics in base as confirmed by high-resolution transmission electron microscope, synchrotron X-ray absorption spectroscopy, and electron energy loss spectroscopy. Due to the in-situ dehydrogenation of ultrathin Co(OH)₂ nanosheets, the catalytic activity of the CoOOH/Co(OH)₂ heterostructures is progressively improved, which exhibit outstanding hydrogen-evolving activity in base requiring a low overpotential of 132 mV to afford 10 mA/cm² with very fast reaction kinetics after 60 h dehydrogenation. The gradually improved catalytic performance for the CoOOH/Co(OH)₂ is probably due to the enhanced H*-adsorption induced by the synergistic effect of heterostructures and better conductivity of CoOOH relative to electrically insulating Co(OH)₂. This work will open the opportunity for a new family of transition metal hydroxides/oxyhydroxides as active HER catalysts, and also highlight the importance of using in situ techniques to construct precious metal-free efficient catalysts for alkaline hydrogen evolution.     

Crystal structure, microstructure and reducibility of LaNixCo1−xO3 and LaFexCo1−xO3 Perovskites (0<x≤0.5)

Nickel and iron substituted LaCoO₃ with rhombohedrally distorted perovskite structure were obtained in the temperature range of 600-900 °C by thermal decomposition of freeze-dried citrates and by the Pechini method. The crystal structure, morphology and defective structure of LaCo_1−xNi_xO₃ and LaCo_1−xFe_xO₃ were characterized by X-ray diffraction and neutron powder diffraction, TEM and SEM analyses and electron paramagnetic resonance spectroscopy. The reducibility was tested by temperature programmed reduction with hydrogen. The products of the partial and complete reduction were determined by ex-situ XRD experiments. The replacement of Co by Ni and Fe led to lattice expansion of the perovskite structure. For perovskites annealed at 900 °C, there was a random Ni, Fe and Co distribution. The morphology of the perovskites does not depend on the Ni and Fe content, nor does it depend on the type of the precursor used. LaCo_1−xNi_xO₃ perovskites (x>0.1) annealed at 900 °C are reduced to Co/Ni transition metal and La₂O₃ via the formation of oxygen deficient Brownmillerite-type compositions. For LaCo_1−xNi_xO₃ annealed at 600 °C, Co/Ni metal, in addition to oxygen-deficient perovskites, was formed as an intermediate product at the initial stage of the reduction. The interaction of LaCo_1−xFe_xO₃ with H₂ occurs by reduction of Co³⁺ to Co²⁺ prior to the Fe³⁺ ions. The reducibility of Fe-substituted perovskites is less sensitive towards the synthesis procedure in comparison with that of Ni substituted perovskites.     

Flame Spray Pyrolysis for Finding Multicomponent Nanomaterials with Superior Electrochemical Properties in the CoOx‐FeOx System for Use in Lithium‐Ion Batteries

High‐temperature flame spray pyrolysis is employed for finding highly efficient nanomaterials for use in lithium‐ion batteries. CoO_x‐FeO_x nanopowders with various compositions are prepared by one‐pot high‐temperature flame spray pyrolysis. The Co and Fe components are uniformly distributed over the CoO_x‐FeO_x composite powders, irrespective of the Co/Fe mole ratio. The Co‐rich CoO_x‐FeO_x composite powders with Co/Fe mole ratios of 3:1 and 2:1 have mixed crystal structures with CoFe₂O₄ and Co₃O₄ phases. However, Co‐substituted magnetite composite powders prepared from spray solutions with Co and Fe components in mole ratios of 1:3, 1:2, and 1:1 have a single phase. Multicomponent CoO_x‐FeO_x powders with a Co/Fe mole ratio of 2:1 and a mixed crystal structure with Co₃O₄ and CoFe₂O₄ phases show high initial capacities and good cycling performance. The stable reversible discharge capacities of the composite powders with a Co/Fe mole ratio of 2:1 decrease from 1165 to 820 mA h g^?1 as the current density is increased from 500 to 5000 mA g^?1; however, the discharge capacity again increases to 1310 mA h g^?1 as the current density is restored to 500 mA g^?1.     

Features of phase formation and state of iron in the quasibinary system FeTe1.65-TiTe1.65

A series of tellurides Fe_xTi_1?x Te_1.65 (x = 0, 0.1, 0.2 …, 1.0) synthesized at 850°C were studied by X-ray phase and X-ray fluorescent analysis and Møssbauer spectroscopy on ⁵⁷Fe. In this series two solid solutions are formed: phases I and II with homogeneity regions within the limits of 0 ≤ x ≤ 0.3 and 0.9 ≤ x ≤ 1.0, respectively. Iron in this series exists in two various states: Fe²⁺ _sym and Fe²⁺ _asym as differentiated from the series of tellurides Fe_xTi_1?x Te_1.45 where three states of iron Fe²⁺ _sym, Fe²⁺ _asym, and Fe⁰ were found. On passing from Fe_xTi_1?x Te_1.45 to Fe_xTi_1?x Te_1.65 the number of formed phases decreases, and phase relations become simpler. The absence of Fe⁰ from phase I of tellurides Fe_xTi_1?x Te_1.65 can point to the fact that TiTe_1.45 and TiTe_1.65 belong to different homogeneity regions.     

Interactions Magnetiques dans quelques Ferrites Oxyfluores a Structure Spinelle de Formule ZnxMFe2−xO4–xFx (M ? Fe,Co, Ni)

Magnetic interactions in some oxyfluoroferrites of spinel structure with the formula Zn_xMe_2?xO_4?xFx (M = Fe, Co, Ni) Whereas the ferromagnetic spin arrangement of the B-cations is not modified by the Zn²⁺?Fe³⁺ substitution in the ZnFe[Fe₂₊Fe³⁺]O_4?xF_x (0 ≤ x ≤ 0,50) spinel, this same substitution leads to a spin canting in the ZnFe[Co₂₊Fe³⁺]O_4?xF_x and ZnFe[Ni₂₊Fe³⁺]O_4?xF_x (0 ≤ x ≤ 0,80) simples. The difference in the magnetic behaviors with regard to the AB and BB interactions can be explained on the basis of the magnetic exchange theory.     

Topochemical Synthesis of Two‐Dimensional Transition‐Metal Phosphides Using Phosphorene Templates

Transition‐metal phosphides (TMPs) have emerged as a fascinating class of narrow‐gap semiconductors and electrocatalysts. However, they are intrinsic nonlayered materials that cannot be delaminated into two‐dimensional (2D) sheets. Here, we demonstrate a general bottom‐up topochemical strategy to synthesize a series of 2D TMPs (e.g. Co₂P, Ni₁₂P₅, and Co_xFe_2?xP) by using phosphorene sheets as the phosphorus precursors and 2D templates. Notably, 2D Co₂P is a p‐type semiconductor, with a hole mobility of 20.8 cm² V^?1 s^?1 at 300 K in field‐effect transistors. It also behaves as a promising electrocatalyst for the oxygen evolution reaction (OER), thanks to the charge‐transport modulation and improved surface exposure. In particular, iron‐doped Co₂P (i.e. Co_1.5Fe_0.5P) delivers a low overpotential of only 278 mV at a current density of 10 mA cm^?2 that outperforms the commercial Ir/C benchmark (304 mV).     

The Stability of α‐Hydroperoxyalkyl Radicals

High‐level ab initio and Born–Oppenheimer molecular dynamic calculations have been carried out on a series of hydroperoxyalkyl (α‐QOOH) radicals with the aim of investigating the stability and unimolecular decomposition mechanism into QO+OH of these species. Dissociation was shown to take place through rotation of the C?O(OH) bond rather than through elongation of the CO?OH bond. Through the C?O(OH) rotation, the unpaired electron of the radical overlaps with the electron density on the O?OH bond, and from this overlap the C=O π bond forms and the O?OH bond breaks spontaneously. The CH₂OOH, CH(CH₃)OOH, CH(OH)OOH, and α‐hydroperoxycycloheptadienyl radical were found to decompose spontaneously, but the CH(CHO)OOH has a decomposition energy barrier of 5.95 kcal mol^?1 owing to its steric and electronic features. The systems studied in this work provide the first insights into how structural and electronic effects govern the stabilizing influence on elusive α‐QOOH radicals.     

Thermal behavior of Co<Subscript>x</Subscript>Fe<Subscript>3−x</Subscript>O<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> nanocomposites obtained by a modified sol–gel method

The thermal behavior of Co_xFe_3?xO₄/SiO₂ nanocomposites obtained by direct synthesis starting from nonahydrate ferric nitrate and hexahydrate cobalt nitrate in different ratios with and without the addition of 1,4-butanediol was studied. For the synthesis of Co_xFe_3?xO₄ (x = 0.5–2.5) dispersed in the silica matrix a wide Co/Fe molar ratio was used. The decomposition processes, formation of crystalline phases, gases evolvement and mass changes during gels annealing at different temperatures were assessed by thermal analysis. The absence of succinate precursor and a low mass loss were observed in the case of the gel obtained in the absence of 1,4-butanediol. In case of gels obtained using a stoichiometric ratio of Co/Fe, no clear delimitation between Co and Fe succinates was observed, while for samples with a Fe or Co excess, the formation of the two succinates was observed. The evolution of the crystalline phase after annealing (673, 973 and 1273 K) investigated by X-ray diffraction analysis and Fourier transformed infrared spectrometry revealed that in samples with Fe excess, stoichiometric Fe/Co ratio or low Co excess, the cobalt ferrite (CoFe₂O₄) was obtained as a single phase, while in samples with higher cobalt excess, olivine (Co₂SiO₄) as a main phase, cobalt oxide and CoFe₂O₄ as secondary phases were obtained after annealing at 1273 K. The SEM images confirmed the nanoparticles embedding in the silica matrix, while the TEM and X-ray diffraction data showed that the obtained nanoparticles’ size was below 10 nm in most samples.     

Ultra‐small,Uniform, and Single bcc‐Phased FexCo1‐x/Graphitic Shell Nanocrystals for T1 Magnetic Resonance Imaging Contrast Agents

We have synthesized ultra‐small and uniform Fe_xCo_1‐x/graphitic carbon shell (Fe_xCo_1‐x/GC) nanocrystals (x=0.13, 0.36, 0.42, 0.50, 0.56, and 0.62, respectively) with average diameters of <4 nm by thermal decomposition of metal precursors in approximately 60 nm MCM‐41 and methane CVD. The composition of the Fe_xCo_1‐x/GC nanocrystals can be tuned by changing the Fe:Co ratios of the metal precursors. The Fe_xCo_1‐x/GC nanocrystals show superparamagnetic properties at room temperature. The Fe_0.50Co_0.50/GC, Fe_0.56Co_0.44/GC, and Fe_0.62Co_0.38/GC nanocrystals have a single bcc FeCo structure, whereas the Fe_0.13Co_0.87/GC, Fe_0.36Co_0.64/GC, and Fe_0.42Co_0.58/GC nanocrystals have a mixed structure of bcc FeCo and fcc Co. The single bcc‐phased Fe_xCo_1‐x/GC nanocrystals functionalized with phospholipid–poly(ethylene glycol) (PL–PEG) in phosphate buffered saline (PBS) are demonstrated to be excellent T₁ MRI contrast agents.     

Solid state reaction synthesis of filled skutterudite compounds (Ce or Y)yFexCo4-xSb12 and the effect of filling atoms Ce or Y on lattice thermal conductivity

The synthesis of filled skutterudite compounds (Ce or Y)yFexCo₄-xSb12, through a solid state reaction using chloride of Ce or Y, high purity powder of Co, Fe, and Sb as starting materials, was investigated. (Ce or Y)yFexCo₄-xSb12 (x = 0 1.0,y = 0 0.15) compounds were obtained at 850 1 123 K. The results of Rietveld analysis demonstrate that (Ce or Y)yFexCo₄-xSb12 synthesized by a solid state reaction possesses a filled skutterudite structure. The filling fraction of Ce or Y obtained by Rietveld analysis agrees well with the composition obtained by chemical analysis. The lattice constant of CeyFexCo₄-xSb12 increases with increasing substitution of Fe at Co sites, and with an increasing Ce filling fraction in the Sb-dodecahedron voids. The lattice thermal conductivity of (Ce or Y)yFexCo₄-xSb12 decreases significantly with an increasing Ce or Y filling fraction in the voids and with substitution of Fe at Co sites.     

Titanates de cuivre substitués à structure bixbyite: Les composés Cu1−xTi1−xFe2xO3 (0.15 ≤ x ≤ 0.33)

A new bixbyite family, Cu_1?xTi_1?xFe_2xO₃ (0.15 ≤ x ≤ 0.33) has been synthesized and characterized. The unit cell is cubic: a ～ 9.40Å. The X-ray powder diffraction study shows up an isotypism with the (Fe, Mn)₂O₃ compounds. There is a disordered distribution of Cu^II, Ti^IV, and Fe^III over the two cyrstallographic sites: P_I and P_II. P_II is highly distorted (two long MO distances) by the Jahn-Teller effect of Cu^II. The bixbyite structure is described in terms of polyhedra arrangement, as a particular case of the CM₂O₃ family. The cation packing is discussed in relation with the existence of the bixbyite structure for the Cu_1?xTi_1?xFe_2xO₃ compounds. The electrical properties (σ ～ 10^?5(Ω cm)^?1 for x = 0.286 at room temperature) show an electron conduction with probably a hopping mechanism.     

Axial Ligand and Spin‐State Influence on the Formation and Reactivity of Hydroperoxo–Iron(III) Porphyrin Complexes

The present study focuses on the formation and reactivity of hydroperoxo–iron(III) porphyrin complexes formed in the [Fe^III(tpfpp)X]/H₂O₂/HOO^? system (TPFPP=5,10,15,20‐tetrakis(pentafluorophenyl)‐21H,23H‐porphyrin; X=Cl^? or CF₃SO₃^?) in acetonitrile under basic conditions at ?15 °C. Depending on the selected reaction conditions and the active form of the catalyst, the formation of high‐spin [Fe^III(tpfpp)(OOH)] and low‐spin [Fe^III(tpfpp)(OH)(OOH)] could be observed with the application of a low‐temperature rapid‐scan UV/Vis spectroscopic technique. Axial ligation and the spin state of the iron(III) center control the mode of O? O bond cleavage in the corresponding hydroperoxo porphyrin species. A mechanistic changeover from homo‐ to heterolytic O? O bond cleavage is observed for high‐ [Fe^III(tpfpp)(OOH)] and low‐spin [Fe^III(tpfpp)(OH)(OOH)] complexes, respectively. In contrast to other iron(III) hydroperoxo complexes with electron‐rich porphyrin ligands, electron‐deficient [Fe^III(tpfpp)(OH)(OOH)] was stable under relatively mild conditions and could therefore be investigated directly in the oxygenation reactions of selected organic substrates. The very low reactivity of [Fe^III(tpfpp)(OH)(OOH)] towards organic substrates implied that the ferric hydroperoxo intermediate must be a very sluggish oxidant compared with the iron(IV)–oxo porphyrin π‐cation radical intermediate in the catalytic oxygenation reactions of cytochrome P450.     

Chemischer Transport und einige Eigenschaften von Kobalteisensulfid CoyFe1−ySx

Chemical Transport and Some Physical Properties of Cobalt Iron Sulphide Co_yFe_1?yS_x The chemical transport behaviour of the ternary phase Co_yFe_1?yS_x is explicable on the base of a thermodynamic model. Theory and experiments show that using Gel₂ as transport agent the phase Co_yFe_1?yS_x with low contents of sulphur and cobalt (x ≈ 1, y < 0.4) will be transported under deminishing the content of Co and under enrichment of Fe and S whereas by use of HI(NH₄I) as transport agent the transport occurs under enrichment of Co and deminishing the Fe and S contents, respectively. The substitution by Co influences on unit-cell dimensions, on the temperature and heat of the phase transition (2C → 1C) as well as on the resistivity jump and hysteresis in connection with this phase transition.