Hydrothermal Redox Reaction Research Articles

Tuning the K+ Concentration in the Tunnel of OMS-2 Nanorods Leads to a Significant Enhancement of the Catalytic Activity for Benzene Oxidation

OMS-2 nanorods with tunable K(+) concentration were prepared by a facile hydrothermal redox reaction of MnSO4, (NH4)2S2O8, and (NH4)2SO4 at 120 °C by adding KNO3 at different KNO3/MnSO4 molar ratios. The OMS-2 nanorod catalysts are characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption and desorption, inductively coupled plasma, and X-ray photoelectron spectrometry. The effect of K(+) concentration on the lattice oxygen activity of OMS-2 is theoretically and experimentally studied by density functional theory calculations and CO temperature-programmed reduction. The results show that increasing the K(+) concentration leads to a considerable enhancement of the lattice oxygen activity in OMS-2 nanorods. An enormous decrease (ΔT50 = 89 °C; ΔT90 > 160 °C) in reaction temperatures T50 and T90 (corresponding to 50 and 90% benzene conversion, respectively) for benzene oxidation has been achieved by increasing the K(+) concentration in the K(+)-doped OMS-2 nanorods due to the considerable enhancement of the lattice oxygen activity.

ChemInform Abstract: From Order to Disorder and Back Again: In situ Hydrothermal Redox Reactions of Uranium Phosphites and Phosphates.

AbstractCompounds (III)—(VII) are characterized by single crystal XRD, SEM, and UV/VIS/NIR spectroscopy.

From Order to Disorder and Back Again: In Situ Hydrothermal Redox Reactions of Uranium Phosphites and Phosphates

Five new uranium phosphites, phosphates, and mixed phosphate-phosphite compounds were hydrothermally synthesized using H(3)PO(3) as an initial reagent. These compounds are Cs(4)[(UO(2))(8)(HPO(4))(5)(HPO(3))(5)]·4H(2)O (1), Cs[U(IV)(PO(4))(H(1.5)PO(4))](2) (2), Cs(4)[U(IV)(6)(PO(4))(8)(HPO(4))(HPO(3))] (3), Cs(10)[U(IV)(10)(PO(4))(4)(HPO(4))(14)(HPO(3))(5)]·H(2)O (4), and Cs(3)[U(IV)(4)(PO(4))(3)(HPO(4))(5)] (5). The first contains uranium(VI) and the latter four uranium(IV). Of the U(IV) structures, two have extensive disordering among the cesium cation positions, one of which also contains disordering at some of the phosphate-phosphite positions. These intermediate compounds are bookended by nondisordered phases. The isolation of these transitional phases occurred at the higher of the pH conditions attempted here. Both the starting pH and the duration of the reactions have a strong influence on the products formed. Herein, we explore the second series of in situ hydrothermal redox reactions of uranyl nitrate with phosphorous acid and cesium carbonate. The isolation of these disordered crystalline products helps to illuminate the complex reaction pathways that can occur in hydrothermal syntheses.

Effect of giant oxygen vacancy defects on the catalytic oxidation of OMS-2 nanorods

We have developed a novel and facile approach of hydrothermal redox reaction to prepare cryptomelane-type octahedral molecular sieve (OMS-2) nanorods with tunable concentration of oxygen vacancy defects (OVDs). We demonstrate a giant OVD effect on the catalytic performance of OMS-2. Increasing the OVD concentration considerably enhances the lattice oxygen reactivity, thus tremendously promoting the catalytic activity for the oxidation of benzene.

Copper@polypyrrole nanocables

A simple hydrothermal redox reaction between microcrystalline CuOHCl and pyrrole leads to the isolation of striking nanostructures formed by polypyrrole-coated copper nanocables. These multicomponent cables that feature single-crystalline face-centered cubic Cu cores (ca. 300 nm wide and up to 200 μm long) are smoothly coated by conducting polypyrrole, which in addition to its functionality, offers protection against oxidation of the metal core.

ChemInform Abstract: Systematic Evolution from Uranyl(VI) Phosphites to Uranium(IV) Phosphates.

AbstractIn situ hydrothermal redox reactions of uranyl nitrate with phosphorous acid and alkali metal carbonates are explored and six new uranium phosphites, phosphates, and phosphite/phosphate mixed compounds are synthesized hydrothermally and one uranyl phosphite is obtained at room temperature.

Systematic Evolution from Uranyl(VI) Phosphites to Uranium(IV) Phosphates

Six new uranium phosphites, phosphates, and mixed phosphate-phosphite compounds were hydrothermally synthesized, with an additional uranyl phosphite synthesized at room temperature. These compounds can contain U(VI) or U(IV), and two are mixed-valent U(VI)/U(IV) compounds. There appears to be a strong correlation between the starting pH and reaction duration and the products that form. In general, phosphites are more likely to form at shorter reaction times, while phosphates form at extended reaction times. Additionally, reduction of uranium from U(VI) to U(IV) happens much more readily at lower pH and can be slowed with an increase in the initial pH of the reaction mixture. Here we explore the in situ hydrothermal redox reactions of uranyl nitrate with phosphorous acid and alkali-metal carbonates. The resulting products reveal the evolution of compounds formed as these hydrothermal redox reactions proceed forward with time.

Nanometer‐Sized Nickel Hollow Spheres

Hollow nickel spheres of 50–60 nm diameter have different properties from bulk nickel. For example, the authors demonstrate that the spheres exhibit a long-range magnetic-ordering transition at 575 K and enhanced coercivity. The facile synthesis of such spheres by mild hydrothermal redox reaction of nickel dodecylsulfate with NaH2PO2 (see Figure) is described.

Hydrothermal synthesis of two perovskite rare-earth manganites, HoMnO 3 and DyMnO 3

Two perovskite rare-earth manganites RMnO 3 ( R=Ho, Dy) were synthesized from the hydrothermal redox reactions of KMnO 4 and MnCl 2 at 250 °C and characterized by means of X-ray diffraction, scanning electron microscopy and SQUID. They are orthorhombic, whereas the hexagonal phases, which were competitive strongly with the orthorhombic phases in solid-state reactions, are avoided in the hydrothermal systems. The pure metastable manganites may serve as a model for understanding the magnetisms of Jahn–Teller distortion and charge ordering. This new synthetic approach leaves many rooms for new doped or undoped RMnO 3 compounds.

GaAs Nanocrystals via Hydrothermal Redox Reaction.

AbstractFor Abstract see ChemInform Abstract in Full Text.

GaAs Nanocrystals via Hydrothermal Redox Reaction

Abstract GaAs nanocrystals of 35 nm were synthesized via hydrothermal redox reaction of metal gallium with As2O3 and following annealing, which were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectra. The formation mechanism was discussed.

Synthesis and Characterization of a New Hybrid-metallic Complex Containing Mixed-valence CuI/CuII Units Generated by Hydrothermal Redox Reaction

Abstract A new hybrid-metallic complex containing mixed-valence CuI/CuII units, [Cu4(ophen)4(Mo2O7)] (Hophen = 2-hydroxy-1,10-phenanthroline), was hydrothermally synthesized and crystallographically characterized.