Shuliang Yang

Nanoscale Magnetic Stirring Bars for Heterogeneous Catalysis in Microscopic Systems

Nanometer-sized magnetic stirring bars containing Pd nanoparticles (denoted as Fe3 O4 -NC-PZS-Pd) for heterogeneous catalysis in microscopic system were prepared through a facile two-step process. In the hydrogenation of styrene, Fe3 O4 -NC-PZS-Pd showed an activity similar to that of the commercial Pd/C catalyst, but much better stability. In microscopic catalytic systems, Fe3 O4 -NC-PZS-Pd can effectively stir the reaction solution within microdrops to accelerate mass transfer, and displays far better catalytic activity than the commercial Pd/C for the hydrogenation of methylene blue in an array of microdroplets. These results suggested that the Fe3 O4 -NC-PZS-Pd could be used as nanoscale stirring bars in nanoreactors.

One-pot synthesis of sandwich-like reduced graphene oxide@CoNiAl layered double hydroxide with excellent pseudocapacitive properties

Layered double hydroxide is one kind of promising material for pseudocapacitors. However, the poor conductivity limits their applications. One possible way to resolve this problem is to mix them with conductive carbon materials. In this work, we developed a one-pot strategy to synthesize sandwich-like nanocomposites with cobalt nickel aluminum layered double hydroxide growth on both sides of different amounts of reduced graphene oxide (RGO(X)@CoNiAl-LDH, X represents the amount of RGO). Such a unique structure is very beneficial for enhancing the conductivity and electrochemical performance. When used as an electrode material for supercapacitors, RGO(25)@CoNiAl-LDH exhibited the best specific capacitance of 1866 F g−1 at a current density of 1 A g−1 and 1360 F g−1 at 10 A g−1, respectively. Furthermore, they displayed excellent cycling performances without an obvious capacitance decrease after 5000 cycles. Such a simple synthesis method, high specific capacitance, rate capability and exceptional cycling stability of these composites offer great promise in energy storage device applications.

Sandwich-like porous TiO2/reduced graphene oxide (rGO) for high-performance lithium-ion batteries

Sandwich-like porous TiO2/reduced graphene oxide (rGO) composites were prepared through a facile solvothermal method. These composites with porous structures and high electrical conductivity showed high capacity, rate capability and cycling stability when used as an anode electrode material for lithium ion batteries. A reversible capacity of 206 mA h g−1 can be retained at a current rate of 0.1 A g−1 after 200 charge–discharge cycles. Remarkably, a high reversible capacity of ∼128 mA h g−1 at a current density of 5 A g−1 can be obtained.

Graphene-based composite supercapacitor electrodes with diethylene glycol as inter-layer spacer

Diethylene-glycol/graphene nano-composites were produced by a simple mild solvothermal method, in which diethylene glycol was grafted onto the surfaces of reduced graphene oxides (RGO) as an inter-layer spacer to spatially separate graphene sheets, i.e. to prevent the aggregation of graphene single sheets. The presence of diethylene glycol was confirmed by several characterizations, including IR, XPS, and AFM. Because of the chain length and electrolyte affinity of the diethylene glycol spacer, most of the surface area of graphene single layer sheets could be accessed by electrolyte, leading to high capacity as supercapacitor electrodes with an impressive electrochemical capacitance (237.8 F g−1 at a charging current of 0.1 A g−1), outstanding rate performances (182.9 F g−1 at 20 A g−1), and excellent cycling stabilities (less than 5 and 10% decline after 2000 and 10 000 cycles). The diethylene-glycol/graphene nano-composites are thus particularly promising for “high-power densities” and “long cycle life” supercapacitor electrodes.

Hierarchical flowerlike magnesium oxide hollow spheres with extremely high surface area for adsorption and catalysis

Three-dimensionally hierarchical flowerlike MgO hollow spheres with an extremely high surface area of 343 m(2) g(-1) were prepared through a facile and environmentally friendly solvothermal route. The maximum adsorption capacity at natural pH reached 569.7 mg g(-1) for the removal of arsenic in water, which is the highest among all of the reported adsorbents. In addition, flowerlike MgO hollow spheres also displayed excellent catalytic activity and stability for the Claisen-Schmidt condensation reaction as a solid base catalyst.

Nitrogen, phosphorus and sulfur co-doped ultrathin carbon nanosheets as a metal-free catalyst for selective oxidation of aromatic alkanes and the oxygen reduction reaction

Carbon materials have attracted considerable interest as metal-free heterogeneous catalysts owing to their superior physicochemical properties, including low cost, stability, and easily tailorable structures as well as excellent catalytic activity. In this study, we have designed an efficient method to produce ultrathin carbon nanosheets (∼2.2 nm) with multi-heteroatom (nitrogen, phosphorus and sulfur) doping and a high surface area (up to 1198 m2 g−1). This method employs poly(cyclotriphosphazene-co-4,4′-sulfonyldiphenol) (PZS) as the main carbon source and N,P,S-doping sources, while g-C3N4 nanosheets act as the morphology template, extra N doping source and porogen. The doped carbon nanosheets are an excellent metal-free carbocatalyst for selective oxidation of aromatic alkanes in aqueous solution and electrochemical catalyst for the oxygen reduction reaction in an alkaline medium.

Highly Active and Stable Palladium Nanoparticles Encapsulated in a Mesoporous Silica Yolk–Shell Nanoreactor for Suzuki–Miyaura Reactions

A yolk–shell nanoreactor with nitrogen‐doped carbon spheres as the yolk and mesoporous silica (mSiO2) as the shell, together with Pd nanoparticles uniformly encapsulated in the void space, were prepared. They showed excellent catalytic activity and stability in the Suzuki–Miyaura reaction between bromobenzene and phenylboronic acid with 99 % yield in 5 min.

Improving the electrochemical performance of Fe3O4 nanoparticles via a double protection strategy through carbon nanotube decoration and graphene networks

Iron oxide is a promising anode material for lithium ion batteries, but it usually exhibits poor electrochemical property because of its poor conductivity and large volume variation during the lithium uptake and release processes. In this work, a double protection strategy for improving electrochemical performance of Fe3O4 nanoparticles through the use of decoration with multi-walled carbon nanotubes and reduced graphene oxides networks has been developed. The resulting MWCNTs-Fe3O4-rGO nanocomposites exhibited excellent cycling performance and rate capability in comparison with MWCNTs-Fe3O4, MWCNTs-Fe3O4 physically mixed with rGO, and Fe3O4-rGO. A reversible capacity of ∼680 mA·h·g−1 can be maintained after 100 cycles under a current density of 200 mA·g−1.

The ionic liquid microphase enhances the catalytic activity of Pd nanoparticles supported by a metal–organic framework

Here we demonstrate the utilization of the ionic liquid (IL) micro-phase for enhancing the catalytic activities of the metal nanoparticles supported on a MOF. The IL microphase offers an excellent environment for stabilizing metal nanoparticles. A new heterogeneous catalyst Pd/IL/MOF is developed, which combines the advantages of highly dispersed small Pd nanoparticles, the IL microphase and a porous MOF. The as-synthesized Pd/IL/MOF catalysts have shown high catalytic activity and reusability for selective hydrogenation under mild conditions.

Amines functionalized C60 as solid base catalysts for Knoevenagel condensation with high activity and stability

Four kinds of amines functionalized C60 were prepared through an amination reaction of C60 with organic amines. Their surface structures and basic properties were studied by Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and temperature-programmed desorption (TPD) with CO2 as the probe molecule. When used as solid base catalysts, N-aminoethylpiperazine functionalized C60 (C60-AEP) showed the best catalytic activity in the Knoevenagel condensation reaction due to the highest basic strength. In addition, the C60-AEP catalyst also showed impressive catalytic stability. All these features endowed C60-AEP with characteristics of both homogeneous and heterogeneous catalysts. More interestingly, chiral L-lysine functionalized C60 (C60-L-L) can be used for asymmetric intermolecular aldol reactions.