Hongyan Miao

In situ light-assisted preparation of MoS2 on graphitic C3N4 nanosheets for enhanced photocatalytic H2 production from water

MoS2-decorated graphitic C3N4 (g-C3N4/MoS2) photocatalysts were prepared by a simple and scalable in situ light-assisted method. In this process, MoS2 was formed from the reduction of [MoS4]2− by photogenerated electrons, and was then loaded in situ on the electron outlet points of g-C3N4. The g-C3N4/MoS2 composite was well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy (Raman), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), and ultraviolet visible diffuse reflection spectroscopy (UV-DRS). The g-C3N4/MoS2 photocatalysts showed good photocatalytic H2 evolution activity. When the loading amount of MoS2 was increased to 2.89 wt% (g-C3N4/MoS2-2.89%), the highest H2 evolution rate (252 μmol g−1 h−1) was obtained. In addition, g-C3N4/MoS2-2.89% presented stable photocatalytic H2 evolution ability (no noticeable degradation of photocatalytic H2 evolution was detected in 18 h) and good natural light driven H2 evolution ability (the H2 evolution rate was 320 μmol g−1 h−1). A possible photocatalytic mechanism of the MoS2 cocatalyst for the improvement of the photocatalytic activity of g-C3N4 is proposed, where MoS2 can efficiently promote the separation of the photogenerated electrons and holes of g-C3N4, consequently enhancing the H2 evolution activity; this mechanism is supported by the photoluminescence spectroscopy and photoelectrochemical analyses.

Simple one-pot synthesis of ZnO/Ag heterostructures and the application in visible-light-responsive photocatalysis

The development of efficient visible-light-driven photocatalysts remains one of the greatest scientific challenges of this century. In this paper, visible light active ZnO/Ag heterostructures have been synthesized on a large-scale by a simple one-pot synthesis method. The influence of the Zn/Ag ratio on the properties of heterostructures was investigated in detail. In light of the formation process of heterostructures, ZnO rods and Ag nanoparticles can link each other by strong bonds due to the bridging effect of NH3, which is found to be essential for the efficient visible-light-responsive activity and stability. These heterostructures were characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray fluorescence, Raman and UV-vis spectroscopy. These results indicate that ZnO/Ag composition is well-constructed with a band gap of 2.85 eV. Moreover, photocatalytic experiments show that these ZnO/Ag heterostructures are robust and exhibit high photocatalytic activity for the efficient separation of electron–hole pairs and the subsequent generation of hydroxyl radicals.

Iridium–CNP complex catalyzed cross-coupling of primary alcohols and secondary alcohols by a borrowing hydrogen strategy

A highly efficient C–C bond formation has been developed through the cross-coupling of primary and secondary alcohols. The corresponding functionalized ketones were obtained with an iridium–CNP complex as a catalyst through the borrowing hydrogen strategy. The present methodology provides an easy alternative method to aldol reaction derivatives. More importantly, the complexes were also effective catalysts for the alkylation of an aromatic amine with a tertiary alkyl amine.

Simple hydrothermal preparation of α-, β-, and γ-MnO2 and phase sensitivity in catalytic ozonation

The investigation of the roles of bonds and phases in catalysis is of great significance for designing novel catalysts and proposing mechanisms. Hindered by the lack of comparable catalyst samples, the influence of bonds and phases on the instantaneous reaction between ozone and MnO2 is still unknown. In this paper, α-, β-, and γ-MnO2 were prepared through a uniform hydrothermal method, and the phase sensitivity of the manganese dioxide catalysts in the ozonation process was investigated. Raman spectra indicated that bands transformed to a larger range in the window of 550–700 cm−1, which is considered to be the fingerprint region of manganese dioxides. During catalytic ozonation, ozone reacted with particular Mn–O bonds to generate more powerful oxygen species, leading to better oxidation efficiency compared to single ozonation. The active bonds, which are favourable to the activation of ozone, include bonds belonging to the pyrolusite type structure of γ-MnO2, corresponding to the [MnO6] octahedral frameworks of β-MnO2 and perpendicular to the direction of the [MnO6] octahedral double chains of α-MnO2. Thermogravimetric analysis confirmed that both active surface oxygen and lattice oxygen were responsible for the catalytic activity of α-MnO2, while lattice oxygen and the bonded manganese of MnO2 contributed to the catalytic activity of β- and γ-MnO2.

A new p-metal-n structure AgBr-Ag-BiOBr with superior visible-light-responsive catalytic performance.

A novel visible-light-driven AgBr-Ag-BiOBr photocatalyst was synthesized by a facile hydrothermal method. Taking advantage of both p-n heterojunctions and localized surface plasmon resonance, the p-metal-n structure exhibited a superior performance concerning degradation of methyl orange under visible-light irradiation (λ>420 nm). A possible photodegradation mechanism in the presence of AgBr-Ag-BiOBr composites was proposed, and the radical species involved in the degradation reaction were investigated. HO2(⋅)/(⋅)O2(-) played the same important role as (⋅)OH in the AgBr-Ag-BiOBr photocatalytic system, and both the electron and hole were fully used for degradation of organic pollutants. A dual role of metallic Ag in the photocatalysis was proposed, one being surface plasmon resonance and the other being an electron-hole bridge. Due to the distinctive p-metal-n structure, the visible-light absorption, the separation of photogenerated carriers and the photocatalysis efficiency were greatly enhanced.

Synthesis, characterization, thermal properties of silicon(IV) compounds containing guanidinato ligands and their potential as CVD precursors

The title compounds of the type (Me3Si)2N–C(N′R)(–N′′RSiMe3) (with R = iPr or Cy) as potential CVD precursors have been synthesized and characterized by X-ray diffraction, 1H NMR, 13C NMR, 29Si NMR and elemental analysis where necessary. Among these characterizations, solid-/liquid-state 29Si NMR were accomplished to study their behavior in the solid and solution. Thermal properties including stability, volatility, transport behavior and vapour pressure were evaluated by thermogravimetric analysis (TGA) to confirm that they are suitable for the CVD procedure. Deposition was accomplished in a hot wall CVD reactor system, which preliminarily verified the ability of these compounds as CVD precursors.