Jie-Sheng Chen

Metal-Free Activation of Dioxygen by Graphene/g-C3N4 Nanocomposites: Functional Dyads for Selective Oxidation of Saturated Hydrocarbons

Graphene sheet/polymeric carbon nitride nanocomposite (GSCN) functions as a metal-free catalyst to activate O(2) for the selective oxidation of secondary C-H bonds of cyclohexane. By fine-tuning the weight ratio of graphene and carbon nitride components, GSCN offers good conversion and high selectivity to corresponding ketones. Besides its high stability, this catalyst also exhibits high chemoselectivity for secondary C-H bonds of various saturated alkanes and, therefore, should be useful in overcoming challenges confronted by metal-mediated catalysis.

Extended Structures and Physicochemical Properties of Uranyl–Organic Compounds

The ability of uranium to undergo nuclear fission has been exploited primarily to manufacture nuclear weapons and to generate nuclear power. Outside of its nuclear physics, uranium also exhibits rich chemistry, and it forms various compounds with other elements. Among the uranium-bearing compounds, those with a uranium oxidation state of +6 are most common and a particular structural unit, uranyl UO(2)(2+) is usually involved in these hexavalent uranium compounds. Apart from forming solids with inorganic ions, the uranyl unit also bonds to organic molecules to generate uranyl-organic coordination materials. If appropriate reaction conditions are employed, uranyl-organic extended structures (1-D chains, 2-D layers, and 3-D frameworks) can be obtained. Research on uranyl-organic compounds with extended structures allows for the exploration of their rich structural chemistry, and such studies also point to potential applications such as in materials that could facilitate nuclear waste disposal. In this Account, we describe the structural features of uranyl-organic compounds and efforts to synthesize uranyl-organic compounds with desired structures. We address strategies to construct 3-D uranyl-organic frameworks through rational selection of organic ligands and the incorporation of heteroatoms. The UO(2)(2+) species with inactive U═O double bonds usually form bipyramidal polyhedral structures with ligands coordinated at the equatorial positions, and these polyhedra act as primary building units (PBUs) for the construction of uranyl-organic compounds. The geometry of the uranyl ions and the steric arrangements and functionalities of organic ligands can be exploited in the the design of uranyl--organic extended structures, We also focus on the investigation of the promising physicochemical properties of uranyl-organic compounds. Uranyl-organic materials with an extended structure may exhibit attractive properties, such as photoluminescence, photocatalysis, photocurrent, and photovoltaic responses. In particular, the intriguing, visible-light photocatalytic activities of uranyl-organic compounds are potentially applicable in decomposition of organic pollutants and in water-splitting with the irradiation of solar light. We ascribe the photochemical properties of uranyl-organic compounds to the electronic transitions within the U═O bonds, which may be affected by the presence of organic ligands.

Surface and Interface Engineering of Electrode Materials for Lithium-Ion Batteries

Lithium-ion batteries are regarded as promising energy storage devices for next-generation electric and hybrid electric vehicles. In order to meet the demands of electric vehicles, considerable efforts have been devoted to the development of advanced electrode materials for lithium-ion batteries with high energy and power densities. Although significant progress has been recently made in the development of novel electrode materials, some critical issues comprising low electronic conductivity, low ionic diffusion efficiency, and large structural variation have to be addressed before the practical application of these materials. Surface and interface engineering is essential to improve the electrochemical performance of electrode materials for lithium-ion batteries. This article reviews the recent progress in surface and interface engineering of electrode materials including the increase in contact interface by decreasing the particle size or introducing porous or hierarchical structures and surface modification or functionalization by metal nanoparticles, metal oxides, carbon materials, polymers, and other ionic and electronic conductive species.

One-pot synthesis of Ag–Fe3O4 nanocomposite: a magnetically recyclable and efficient catalyst for epoxidation of styrene

With the assistance of PVP, a novel magnetically recyclable Ag-based catalyst has been synthesized in one pot, and it is found that this catalyst is highly efficient in selectively catalyzing styrene conversion to styrene oxide.

Montmorillonite-Supported Ag/TiO2 Nanoparticles: An Efficient Visible-Light Bacteria Photodegradation Material

Montmorillonite (MMT)-supported Ag/TiO(2) composite (Ag/TiO(2)/MMT) has been prepared through a one-step, low-temperature solvothermal technique. Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) reveal that the Ag particles coated with TiO(2) nanoparticles are well-dispersed on the surface of MMT in the composite. As a support for the Ag/TiO(2) composite, the MMT prevents the loss of the catalyst during recycling test. This Ag/TiO(2)/MMT composite exhibits high photocatalytic activity and good recycling performance in the degradation of E. coli under visible light. The high visible-light photocatalytic activity of the Ag/TiO(2)/MMT composite is ascribed to the increase in surface active centers and the localized surface plasmon effect of the Ag nanoparticles. The Ag/TiO(2)/MMT materials with excellent stability, recyclability, and bactericidal activities are promising photocatalysts for application in decontamination.

Surface Binding of Polypyrrole on Porous Silicon Hollow Nanospheres for Li‐Ion Battery Anodes with High Structure Stability

Uniform porous silicon hollow nano-spheres are prepared without any sacrificial templates through a magnesio-thermic reduction of mesoporous silica hollow nanospheres and surface modified by the following in situ chemical polymerization of polypyrrole. The porous hollow structure and polypyrrole coating contribute significantly to the excellent structure stability and high electrochemical performance of the nanocomposite.

Construction of a microporous inorganic-organic hybrid compound with uranyl units.

A uranium-nickel-organic hybrid compound with micropores has been assembled from a hydrothermal system, and this compound exhibits photocatalytic activities for the degradation of methyl blue as a model pollutant.

Hydrothermal synthesis and photoluminescent properties of ZnWO4 and Eu3+-doped ZnWO4

Abstract Through a hydrothermal reaction route, zinc tungstate (ZnWO 4 ) crystals with various morphologies and particle sizes have been synthesized using sodium tungstate and zinc acetate as the raw materials. Eu 3+ -doped ZnWO 4 was also obtained from hydrothermal systems and the photoluminescent properties of the products were investigated. Significant energy transfer from WO 4 2- groups to Eu 3+ ions has been observed.

Facile Synthesis of Thermal‐ and Photostable Titania with Paramagnetic Oxygen Vacancies for Visible‐Light Photocatalysis

A novel dopant-free TiO(2) photocatalyst (V(o)(.)-TiO(2)), which is self-modified by a large number of paramagnetic (single-electron-trapped) oxygen vacancies, was prepared by calcining a mixture of a porous amorphous TiO(2) precursor, imidazole, and hydrochloric acid at elevated temperature (450 °C) in air. Control experiments demonstrate that the porous TiO(2) precursor, imidazole, and hydrochloric acid are all necessary for the formation of V(o)(.)-TiO(2). Although the synthesis of V(o)(.)-TiO(2) originates from such a multicomponent system, this synthetic approach is facile, controllable, and reproducible. X-ray diffraction, XPS, and EPR spectroscopy reveal that the V(o)(.)-TiO(2) material with a high crystallinity embodies a mass of paramagnetic oxygen vacancies, and is free of other dopant species such as nitrogen and carbon. UV/Vis diffuse-reflectance spectroscopy and photoelectrochemical measurement demonstrate that V(o)(.)-TiO(2) is a stable visible-light-responsive material with photogenerated charge separation efficiency higher than N-TiO(2) and P25 under visible-light irradiation. The V(o)(.)-TiO(2) material exhibits not only satisfactory thermal- and photostability, but also superior photocatalytic activity for H(2) evolution (115 μmol h(-1) g(-1)) from water with methanol as sacrificial reagent under visible light (λ>400 nm) irradiation. Furthermore, the effects of reaction temperature, ratio of starting materials (imidazole:TiO(2) precursor) and calcination time on the photocatalytic activity and the microstructure of V(o)(.)-TiO(2) were elucidated.

Activating Cobalt Nanoparticles via the Mott–Schottky Effect in Nitrogen-Rich Carbon Shells for Base-Free Aerobic Oxidation of Alcohols to Esters

Heterogeneous catalysts of inexpensive and reusable transition-metal are attractive alternatives to homogeneous catalysts; the relatively low activity of transition-metal nanoparticles has become the main hurdle for their practical applications. Here, the de novo design of a Mott-Schottky-type heterogeneous catalyst is reported to boost the activity of a transition-metal nanocatalyst through electron transfer at the metal/nitrogen-doped carbon interface. The Mott-Schottky catalyst of nitrogen-rich carbon-coated cobalt nanoparticles (Co@NC) was prepared through direct polycondensation of simple organic molecules and inorganic metal salts in the presence of g-C3N4 powder. The Co@NC with controllable nitrogen content and thus tunable Fermi energy and catalytic activity exhibited a high turnover frequency (TOF) value (8.12 mol methyl benzoate mol-1 Co h-1) for the direct, base-free, aerobic oxidation of benzyl alcohols to methyl benzoate; this TOF is 30-fold higher than those of the state-of-the-art transition-metal-based nanocatalysts reported in the literature. The presented efficient Mott-Schottky catalyst can trigger the synthesis of a series of alkyl esters and even diesters in high yields.