Xujie Yang

Effect of Graphene Oxide on the Properties of Its Composite with Polyaniline

Graphene oxide, a single layer of graphite oxide (GO), has been used to prepare graphene oxide/polyaniline (PANI) composite with improved electrochemical performance as supercapacitor electrode by in situ polymerization using a mild oxidant. The composites are synthesized under different mass ratios, using graphite as start material with two sizes: 12 500 and 500 mesh. The result shows that the morphology of the prepared composites is influenced dramatically by the different mass ratios. The composites are proposed to be combined through electrostatic interaction (doping process), hydrogen bonding, and pi-pi stacking interaction. The highest initial specific capacitances of 746 F g(-1) (12 500 mesh) and 627 F g(-1) (500 mesh) corresponding to the mass ratios 1:200 and 1:50 (graphene oxide/aniline) are obtained, compared to PANI of 216 F g(-1) at 200 mA g(-1) by charge-discharge analysis between 0.0 and 0.4 V. The improved capacitance retention of 73% (12 500 mesh) and 64% (500 mesh) after 500 cycles is obtained for the mass ratios 1:23 and 1:19 compared to PANI of 20%. The enhanced specific capacitance and cycling life implies a synergistic effect between two components. This study is of significance for developing new doped PANI materials for supercapacitors.

Preparation and Characterization of Mesoporous Zirconia Made by Using a Poly (methyl methacrylate) Template

Superfine powders of poly (methyl methacrylate) (PMMA) have been prepared by means of an emulsion polymerization method. These have been used as templates in the synthesis of tetragonal phase mesoporous zirconia by the sol–gel method, using zirconium oxychloride and oxalic acid as raw materials. The products have been characterized by infrared spectroscopy, X-ray diffraction analysis, transmission electron microscopy, N2adsorption-desorption isotherms, and pore size distribution. The results indicate that the average pore size was found to be 3.7 nm.

An improvement on sol-gel method for preparing ultrafine and crystallized titania powder

Abstract TiO 2 nanoparticles were prepared using a sol-gel method with inorganotitanates and polyethylene glycol (PEG). However, the way TiO 2 particles were obtained from the dry gel was not by calcining but by redissolving the dry gel which had been treated at 100°C, thereby releasing the particles. The TiO 2 powder prepared in this manner was ultra-fine (∼4 nm) and crystallized (anatase phase) merely by being exposed to 100°C while inside the gel. It was supposed that this low temperature crystallization of TiO 2 results from the special structure of the gel which formed through the linking of TiO(NO 3 ) 2  · H 2 O with PEG chains by a hydrogen bond. This preparation method also has an advantage in environmental protection.

Characterization of perovskite-type LaCoO3 nanocrystals prepared by a stearic acid sol--gel process

Abstracts are not published in this journal

Characterization and size-dependent magnetic properties of Ba3Co2Fe24O41 nanocrystals synthesized through a sol-gel method

Ba3Co2Fe24O41 nanocrystals are synthesized through a stearic acid sol-gel method. The reaction temperatures are dramatically lower than that of the conventional ceramic method. The nanocrystalline powders obtained at 750°C were spherical in shape with grain sizes in the range 15–25 nm and become a plate-like form when the heat-treatment temperature increased. The magnetic properties of these samples are different from those of the bulk Z-type hexagonal ferrite with a lower specific saturation magnetization. This phenomenon can be attributed to the existing of a nonmagnetic layer existing on the surface of the particles. The higher value of the coercivity force is obtained when the particle sizes approximately are equal to 90 nm and assume a single-domain character. The surface composition of the nanocrystalline Co2-Z hexagonal ferrite is different from that of the bulk counterpart material with a higher content of the Ba element and Co element.

A novel yet simple strategy to fabricate visible light responsive C,N-TiO2/g-C3N4 heterostructures with significantly enhanced photocatalytic hydrogen generation

In this report, we first successfully designed and fabricated novel C,N co-doped titanium dioxide nanoparticles/graphite-like carbon nitrogen ultrathin nanosheets (C,N-TiO2 NPs/g-C3N4) heterostructures, wherein the C,N-TiO2 NPs were in situ grown on the porous g-C3N4 ultrathin nanosheets (NSs) by a simple one-pot solvothermal route with the assistance of concentrated nitric acid. The resulting C,N-TiO2 NPs/g-C3N4 nanocomposite photocatalysts were systematically characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), diffuse reflectance spectroscopy (DRS), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL) spectroscopy, transient photocurrent–time (I–t) curves and electrochemical impedance spectroscopy (EIS) Nyquist plots. The photocatalytic ability was evaluated by photocatalytic water splitting for hydrogen evolution. These studies indicate that C,N-TiO2 NPs/g-C3N4 composites exhibit superior ability for hydrogen generation compared to single C,N-TiO2 NPs and pure g-C3N4 NSs under visible light illumination. The optimal composites with 3 wt% C,N-TiO2 NPs/g-C3N4 showed the highest hydrogen evolution rate of 39.18 μmol g−1 h−1, which is about 10.9 and 21.3 times higher than those of C,N-TiO2 NPs and pure g-C3N4 NSs, respectively. The improved photocatalytic H2 evolution can be attributed to improved optical absorption and the lengthening lifetime of charge carrier pairs as a result of the C,N elemental codoping and the construction of intimate heterogeneous interfaces. This simple and feasible method for the fabrication of highly-efficient visible light responsive catalysts provides a great applied potential in energy generation.

Study on the catalytic effect of NiO nanoparticles on the thermal decomposition of TEGDN/NC propellant

The catalytic effect of NiO nanoparticles on the thermal decomposition of double-base propellant composed of nitrocellulose (NC) and triethylene glycol dinitrate (TEGDN) has been investigated by thermogravimetry-mass spectrometry (TG-MS) coupling technique. It was shown that adding 2% of NiO nanoparticles to TEGDN/NC propellant can accelerate the thermal decomposition process after around 188 degrees C TG-MS analysis indicated that NiO nanoparticles have resulted in the increase in intensity (peak area) of m/z=27, 28, and 29 MS signals, but the decrease in the intensity of m/z=18, 30, 44 and 46 (peak 2) MS signals during the thermal decompsition. The catalytic mechanism was also discussed in this paper.

Study on the synthesis and ion-exchange properties of layered titanate Na2Ti3O7 powders with different sizes

Layered titanate Na2Ti3O7 powders with varying sizes were prepared by solid-state reaction of Na2CO3 and TiO2 with different average particle sizes. The structures of the titanates and the products which had undergone H+ and Ag+ exchange were investigated by XRD, TEM and BET analysis. The influence of the particle size of starting material TiO2 on the reaction rate, the particle size and ion-exchange property of the resulting products was studied. It is found that nanometer sized TiO2 facilitates the solid-state reaction and leads to the formation of ultrafine titanate. The H+-exchange property is improved by decreasing the particle size of Na2Ti3O7 and the small sized layered titanate can be exfoliated easily by AgNO3 solution.

Well-Combined Magnetically Separable Hybrid Cobalt Ferrite/Nitrogen-Doped Graphene as Efficient Catalyst with Superior Performance for Oxygen Reduction Reaction.

Catalysts with low-cost, high activity and stability toward oxygen reduction reaction (ORR) are extremely desirable, but its development still remains a great challenge. Here, a novel magnetically separable hybrid of multimetal oxide, cobalt ferrite (CoFe2O4), anchored on nitrogen-doped reduced graphene oxide (CoFe2O4/NG) is prepared via a facile solvothermal method followed by calcination at 500 °C. The structure of CoFe2O4/NG and the interaction of both components are analyzed by several techniques. The possible formation of Co/Fe-N interaction in the CoFe2O4/NG catalyst is found. As a result, the well-combination of CoFe2O4 nanoparticles with NG and its improved crystallinity lead to a synergistic and efficient catalyst with high performance to ORR through a four-electron-transfer process in alkaline medium. The CoFe2O4/NG exhibits particularly comparable catalytic activity as commercial Pt/C catalyst, and superior stability against methanol oxidation and CO poisoning. Meanwhile, it has been proved that both nitrogen doping and the spinel structure of CoFe2O4 can have a significant contribution to the catalytic activity by contrast experiments. Multimetal oxide hybrid demonstrates better catalysis to ORR than a single metal oxide hybrid. All results make the low-cost and magnetically separable CoFe2O4/NG a promising alternative for costly platinum-based ORR catalyst in fuel cells and metal-air batteries.

Vibrational spectroscopic study of o-, m- and p-hydroxybenzylideneaminoantipyrines.

Three structurally similar antipyrine derivatives of o-hydroxybenzylideneaminoantipyrine (o-HBAP), m-hydroxybenzylideneaminoantipyrine (m-HBAP) and p-hydroxybenzylideneaminoantipyrine (p-HBAP) were characterized by FT-IR, FT-Raman experimental techniques and density functional theoretical (DFT) calculations. The comparisons between the calculated and experimental results covering molecular structures, assignments of fundamental vibrational modes and thermodynamic properties were investigated. The optimized molecular geometries agree well with the corresponding experimental values by comparing with the XRD data. The comparisons and assignments of the vibrational frequencies indicate that the experimental spectra also coincide satisfactorily with those of theoretically simulated spectrograms except the hydrogen-bond coupling infrared vibrations, and compounds can be distinguished by the IR and Raman spectra due to the differences of the hydroxyl-substituted positions and molecular packing, and the strong Raman scattering activities of the compounds are tightly relative to the molecular conjugative moieties linked through the Schiff base imines. The thermodynamic functions and their correlations with temperatures were also obtained from the theoretical harmonic frequencies.