氧化石墨烯/H2O2可见光催化性能影响因素

为了研究氧化石墨烯/H₂O₂可见光催化处理含难降解有机物废水影响因素,用改进的Hummers法制备了氧化石墨烯(GO),通过扫描电镜(SEM)、电子能谱(EDS)、拉曼光谱对GO的微观形貌、成分及结构进行了表征.以甲基橙(MO)为难降解有机物代表,通过改变光照、pH值以及GO的量探究了不同条件对GO/H₂O₂复合试剂降解甲基橙的光催化效果.研究表明：GO/H₂O₂复合试剂可以通过光催化产生羟基自由基降解污染物,通过改变光照、pH值及GO的量增加自由基含量可提升催化效果; 采用GO/H₂O₂复合试剂比单独使用H₂O₂在48 h内对甲基橙的降解率可提高79.09%(pH=2).用改良的Hummers法制备GO成本较低,采用GO/H₂O₂复合试剂光催化降解甲基橙时,GO用量较少,且不产生危险废弃物,为实际应用中处理难降解有机物污水提供了一个绿色环保、节能高效的思路.     

NiCo2O4/氧化石墨烯复合材料制备与电化学性能研究

为了研究NiCo₂O₄/氧化石墨烯(NiCo₂O₄/GO)复合材料的电化学性能,本文通过先水热合成前驱体再煅烧的方法制备了一系列NiCo₂O₄/GO复合材料.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和电化学方法对其进行物理表征,其中以GO质量浓度为1 mg/mL悬浊液制备出的NiCo₂O₄ /GO-3复合材料呈类海胆状结构.在1 M KOH水溶液中使用循环伏安法、恒电流充/放电法和交流阻抗法研究了NiCo₂O₄/GO复合材料电化学性能.研究表明,与纯NiCo₂O₄相比,制备的NiCo₂O₄ /GO复合材料的比容量和赝电容性能均有明显提高,这主要是由于NiCo₂O₄ /GO复合材料中NiCo₂O₄与GO纳米片的相互作用形成的高孔隙率复合结构;NiCo₂O₄ /GO-3复合材料在电流密度为0.5~3.0 A/g时,比电容超过650 F/g,具有良好的倍率性能和高比容量.采用本文方法合成的NiCo₂O₄/GO复合材料,既提高了其倍率性能又保证了高比容量,是一种良好的超级电容器电极材料.     

Solvothermal synthesis of sheet-like Co3O4 and Ag/Co3O4 nanocomposites and their electrocatalysis performances

Precursors of Co₃O₄ and Ag/Co₃O₄ composites with sheet-like shape were synthesized with assistance of ethylene glycol via a solvothermal process. The final samples were obtained by calcining each precursor at 400 °C. The as-prepared samples were identified and characterized by thermogravimetric analysis (TG) and differential thermal gravimetric (DTG) analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and field emission scanning electron microscopy (FE-SEM). The Co₃O₄ and Ag/Co₃O₄ composite nanosheets were used as electrocatalysts modified on a glassy carbon electrode for p-nitrophenol and H₂O₂ reduction respectively in a basic solution. The electrocatalytic results showed that p-nitrophenol could be reduced by pure Co₃O₄ at a large peak current but a rather higher peak potential, and could be reduced effectively by Ag/Co₃O₄ composites at lower potential. Ag/Co₃O₄ composites with 6% Ag displayed the highest electrocatalytic activity for H₂O₂ reduction at the largest peak current and a lower peak potential. The reduction peak potentials of H₂O₂ all reduced a great deal using Ag/Co₃O₄ composite.     

Preparation and characterization of poly(acrylonitrile-co-acrylic acid) nanofibrous composites with Fe3O4 magnetic nanoparticles

Nanofibrous composites are a new class of polymer materials with controlled and tailored properties. Novel Fe₃O₄/poly(acrylonitrile-co-acrylic acid) nanofibrous composites with magnetic behavior have been prepared by a simple electrospinning process. The nanofibrous composites were characterized by X-ray diffraction, field emission scanning electron microscopy and vibrating sample magnetometer. The distribution of Fe₃O₄ nanoparticles inside the nanofibrous composites was investigated by field emission scanning electron microscopy. X-ray diffraction revealed the presence of Fe₃O₄ nanoparticles in the nanofibrous composites. The maximum saturation magnetization for the composites, measured at 300 K, was 30.51 emu/g.     

Facile synthesis of MnV2O6 nanostructures with controlled morphologies

MnV₂O₆ nanostructures including nanorods, nanobelts, and nanosheets, have been synthesized by a facile hydrothermal reaction between Mn(CH₃COO)₂·4H₂O and commercial V₂O₅. The synthesized products are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The influences of synthetic parameters, such as, reaction time, temperature and medium, on the morphologies of the resulting products have been investigated. As the reaction temperatures increase from 120 °C to 180 °C, MnV₂O₆ nanorods and nanobelts are obtained, respectively. The time-dependent experimental results at 180 °C reveal that the sizes of MnV₂O₆ nanobelts increase gradually with the reaction proceeding. Interestingly, as the reaction is carried out with the aid of H₂O₂ solution, flower-like MnV₂O₆ nanosheets are formed.     

Flexible electrochemical biosensors based on O2 plasma functionalized MWCNT

A flexible glucose sensor is fabricated using O₂ plasma-functionalized multiwalled carbon nanotube (MWCNT) films on polydimethylsiloxane (PDMS) substrates and its performance is electrochemically characterized. After enzyme immobilization, the GOD/ MWCNT/Au/PDMS electrode exhibits a sensitivity of 18.15 μA mm^− 2mM^− 1 and a detection limit of 0.01 mM (signal to noise ratio was about 3). This high sensitivity may be attributed to a large enzyme loading and a higher electrocatalytic activity and electron transfer exhibited by O₂ plasma-functionalized CNTs than the pristine CNT, due to some oxygen-contained groups present on the O₂ plasma-functionalized CNT surface, which has been verified by XPS spectrum.     

Influence of SiC, Si3N4 and Al2O3 particles on the structure and properties of electrodeposited Ni

The structure and properties of electrodeposited nickel composites reinforced with inert particles like SiC, Si₃N₄ and Al₂O₃ were compared. A comparison was made with respect to structure, morphology, microhardness and tribological behaviour. The coatings were characterized with optical microscopy, Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) technique. The cross-sectional microscopy studies revealed that the particles were uniformly distributed in all the composites. However, a difference in the surface morphology was revealed from SEM studies. The microhardness studies revealed that Si₃N₄ reinforced composite showed higher hardness compared to SiC and Al₂O₃ composite. This was attributed to the reduced crystallite size of Ni — 12 nm compared to 16 nm (SiC) and 23 nm (Al₂O₃) in the composite coating. The tribological performance of these coatings studied using a Pin-on-disk wear tester, revealed that Si₃N₄ reinforced composite exhibited better wear resistance compared to SiC and Al₂O₃ composites. However, no significant variation in the coefficient of friction was observed for all the three composites.     

A citrate complex process to prepare nanocrystalline PbBi2Nb2O9 at a low temperature

PbBi₂Nb₂O₉ nanocrystals with a perovskite-type structure were successfully synthesized at a relative low temperature via a citrate complex method. Metal ions were dispersed by citric acid in ethanol and ethylene glycol solvent, and then reacted with NH₄H₂[NbO(C₂O₄)₃·3H₂O] to form the gel. XRD results showed that pure PbBi₂Nb₂O₉ nanocrystals could be obtained after calcined treatment of xerogel at 800 °C. The average particles size was 57 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the sintering process led to the agglomeration of the nanoparticles. The photocatalytic test showed that the sample prepared by the citrate complex method exhibited a higher photocatalytic activity than that of the sample prepared by the solid-state reaction.     

Thermal and electrical conductivity of Al(OH)<Subscript>3</Subscript> covered graphene oxide nanosheet/epoxy composites

Al(OH)₃ functionalized graphene composites (Al–GO) were prepared using a simple sol–gel method. In this protocol, graphene oxide (GO) was prepared according to the Hummers method and functionalized to enhance its reactivity with aluminum isopropoxide by a LiAlH₄ treatment. The functionalized graphene sheets were characterized by X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. These analyses confirmed that GO had been fabricated and the Al(OH)₃ layer could have a homogeneous distribution with large and dense coverage onto GO sheets. In addition, the thermal and electrical conductivity of the epoxy composites with GO and Al–GO fillers were measured. The thermal conductivities of the composites with graphene-based fillers were enhanced by the addition of fillers. In particular, the thermal conductivity of GO/epoxy composite containing 3 wt% was approximately two times higher than that of pure epoxy resin. In addition, the electrical conductivity of Al–GO embedded composites degenerated compared to GO composites.     

Synthesis and electrocatalytic activity of multi-walled carbon nanotubes/Cu–Ag nanocomposites

Cu–Ag bimetallic nanoparticles with atomic ratio of 2.1:1 and diameter in the range of 15–30 nm were decorated on acid-treated multi-walled carbon nanotubes by a chemical reduction method, which was characterized by transmission electron microscope (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The Cu–Ag/MWNTs nanocomposites were used to construct a modified electrode toward biosensing of H₂O₂ with a high sensitivity. The catalytic ability of MWNTs/Cu–Ag toward H₂O₂ was much better than that of MWNTs/Cu and MWNTs/Ag, which indicated that there is a cooperation effect between Cu and Ag.     

Surface modification of LiCo1/3Ni1/3Mn1/3O2 with CoAl-MMO for lithium-ion batteries

Layered LiCo_1/3Ni_1/3Mn_1/3O₂ has been modified with Co–Al-mixed metal oxide (CoAl-MMO). The surface-modified materials were characterized by X-ray diffraction, field emission scanning electron microscopy, and galvanostatic charge–discharge cycling. The CoAl-MMO-coated LiCo_1/3Ni_1/3Mn_1/3O₂ had an initial discharge specific capacity of 178.1 mAh g⁻¹ within the potential range of 2.75–4.5 V (vs. Li⁺/Li), and its discharge specific capacity is 175.0 mAh g⁻¹ after 50 cycles, much higher than that of the pristine LiCo_1/3Ni_1/3Mn_1/3O₂ (148.4 mAh g⁻¹). The improvement could be attributed to the CoAl-MMO coating layer that would hinder interaction between LiCo_1/3Ni_1/3Mn_1/3O₂ and electrolyte and stabilize the structure of LiCo_1/3Ni_1/3Mn_1/3O₂. Moreover, DSC showed that the CoAl-MMO-coated LiCo_1/3Ni_1/3Mn_1/3O₂ had a higher thermal stability than the pristine LiCo_1/3Ni_1/3Mn_1/3O₂. Therefore, the CoAl-MMO-coated LiCo_1/3Ni_1/3Mn_1/3O₂ could be a high-performance cathode material for lithium-ion batteries.     

Dielectric properties of Pb[(1?x)(Zr1/2Ti1/2)?x(Zn1/3Ta2/3)]O3 ceramics prepared by columbite and wolframite methods

Polycrystalline samples of Pb[(1 − x)(Zr_1/2Ti_1/2) − x(Zn_1/3Ta_2/3)]O ₃ , where x = 0.1–0.5 were prepared by the columbite and wolframite methods. The crystal structure, microstructure, and dielectric properties of the sintered ceramics were investigated as a function of composition via X-ray diffraction (XRD), scanning electron microscopy (SEM), and dielectric spectroscopy. The results indicated that the presence of Pb(Zn_1/3Ta_2/3)O₃ (PZnTa) in the solid solution decreased the structural stability of overall perovskite phase. A transition from tetragonal to pseudo-cubic symmetry was observed as the PZnTa content increased and a co-existence of tetragonal and pseudo-cubic phases was observed at a composition close to x = 0.1. Examination of the dielectric spectra indicated that PZT–PZnTa exhibited an extremely high relative permittivity at the MPB composition. The permittivity showed a ferroelectric to paraelectric phase transition at 330 °C with a maximum value of 19,600 at 100 Hz at the MPB composition.     

Pt nanoparticles on graphene – polyelectrolyte nanocomposite: Investigation of H2O2 and methanol electrocatalysis

Poly (diallyldimethylammonium chloride) (PDDA) functionalized graphene oxide (GO) decorated with Pt nanoparticles (PtNPs) was obtained and investigated. This hybrid nanocomposite material was morphologically characterized by several instrumental techniques like high-resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) and X-ray diffraction (XRD). Good coverage of crystalline Pt nanoparticles was achieved, the average diameter being 2 nm, meanwhile in the absence of polyelectrolyte the average diameter increased up to 4 nm. The electrocatalytic properties of this hybrid nanocomposite against H₂O₂ and methanol were ascertained by cyclic voltammetry. A modified glassy carbon electrode (GC) was able to reduce H₂O₂ at positive potentials (starting from ∼150 mV vs. Ag/AgCl) meanwhile for methanol the ratio of the forward anodic peak current (I_f) to the reverse anodic peak current (I_b) was 1.42, indicating good tolerance of the catalyst towards the intermediate carbonaceous species accumulated on the electrode surface.     

Preparation and properties of Ti/SnO2-Sb2O5 electrodes by electrodeposition

Sb and Sn coatings were deposited on Ti substrate by the method of cathode deposition, and the Ti/SnO₂-Sb₂O₅ electrodes were obtained by annealing at different temperatures for 3 h. Ti/SnO₂-Sb₂O₅ coating was characterized using technique such as X-ray diffraction (XRD), and scanning electron microscopy (SEM). Ti/SnO₂-Sb₂O₅ electrode calcined at 550 °C exhibits the best catalytic capacity. Ti/SnO₂-Sb₂O₅ electrode obtained by electrodeposition had longer service life and faster degradation capacity compared with that obtained by dip-coating. Accelerated service life tests were carried out in 0.5 mol L^− 1 H₂SO₄ solution with the current density of 100 mA cm^− 2. Service life of Ti/SnO₂-Sb₂O₅ electrode prepared in present study was 15 h, and it was only 0.14 h for Ti/SnO₂-Sb₂O₅ electrode obtained by dip-coating.     

A multilayer MoSi2-SiC-B coating to protect SiC-coated carbon/carbon composites against oxidation

To protect carbon/carbon (C/C) composites against oxidation, a multilayer MoSi₂-SiC-B coating was prepared on the SiC-coated C/C composites by a simple and low-cost slurry method. The phase, microstructure and element distribution of the as-received coating were analyzed using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. The as-received coating could effectively protect C/C composites against oxidation at 850 °C in air for 100 h without mass loss, which exhibits better oxidation protective ability than the multilayer MoSi₂-SiC coating prepared by the same method. At intermediate temperature (850 °C), the excellent oxidation protective ability of the coating is mainly attributed to the formation of the molten B₂O₃ for sealing the microcracks and preventing oxygen from attacking the C/C substrate.     

Synthesis of Sb2S3 peanut-shaped superstructures

Peanut-shaped Sb₂S₃ superstructures have been synthesized via a hydrothermal process at 120 °C for 8 h using hydrochloric acid and antimony O-benzyl dithiocarbonate (benzylxanthate, Sb(S₂COC₇H₇)₃) as starting materials. The powder X-ray diffraction (XRD) pattern shows the product corresponds to the pure orthorhombic phase of Sb₂S₃, the purity and composition of which are further confirmed by X-ray photoelectron spectroscopy (XPS). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies reveal that the peanut-shaped Sb₂S₃ superstructures are aggregated by nanorods. The possible mechanistic pathways in the formation of the structures are discussed.     

Mn<Subscript>3</Subscript>O<Subscript>4</Subscript>/worm-like mesoporous carbon synthesized via a microwave method for supercapacitors

A quick and facile microwave method has been employed to prepare Mn₃O₄/worm-like mesoporous carbon (Mn₃O₄–MC) composites. Structural and morphological characterizations of worm-like mesoporous carbon and Mn₃O₄–MC composites have been carried out using X-ray diffraction, transmission electron microscopy, N₂ adsorption–desorption, and electrochemical measurement. Cyclic voltammograms demonstrate that the Mn₃O₄–MC composites perform improved capacitive behavior at the range of −0.8~0.2 V (vs. Hg/HgO electrode) with reversibility. The Mn₃O₄–MC composite electrode possesses an enhanced specific capacitance of 266 F g⁻¹ at a sweep rate of 1 mV s⁻¹.     

Ferromagnetism in Electrospun Co-doped SrTiO3 Nanofibers

By employing electrospinning technique, subsequent calcination in air and annealing process in hydrogen, uniform Co-doped SrTiO₃ nanofibers with concentrations of Co between 0 and 0.20 were successfully produced. Their morphologies and detailed structures were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray powder diffraction. And, the chemical states of Co were determined by X-ray photoelectron spectroscopy. It was shown that, after calcination, Co²⁺ was well incorporated into the perovskite structure of SrTiO₃, and the nanofibers possessed smooth surface with diameters of 50–100 nm. Magnetic properties of the hydrogen-annealed and -unannealed nanofibers were both measured by physical property measurement system from 50 to 300 K. It was explored that the Co addition and the hydrogen annealing process were both very important to the generation of the observed ferromagnetism in SrTi_1−x Co _x O₃:H₂ nanofibers. In hydrogen-annealed SrTi_0.80Co_0.20O₃:H₂ nanofibers, a saturation magnetization of 0.74 emu/g and an average moment of 0.122 μ_B/Co were obtained. The origins of the enhanced ferromagnetism in SrTi_1−x Co _x O₃:H₂ nanofibers were analyzed according to the chemical state of Co and the mediation of oxygen vacancies.     

Photoluminescence properties of the In2O3 octahedrons synthesized by carbothermal reduction method

In₂O₃ octahedrons were synthesized by carbothermal reduction method. The products were characterized by X-ray diffraction (XRD), energy dispersive X-ray (EDX), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction analysis (SAED) and room-temperature photoluminescence (PL) spectra. The results show that the products are single-crystalline In₂O₃ octahedrons with the arrises length in the range of 400-3000 nm. The PL spectra displays blue and green emission peaks which can be indexed to default and oxygen vacancies; blue-shift and intensity decrease was observed when excitation wavelength decreases from 380 nm to 325 nm. The growth mechanism of the In₂O₃ octahedrons is discussed.     

Mn2O3/carbon aerogel microbead composites synthesized by in situ coating method for supercapacitors

A series of Mn₂O₃/carbon aerogel microbead (Mn₂O₃/CAMB) composites for supercapacitor electrodes have been synthesized by in situ encapsulation method. The structure and morphology of Mn₂O₃/CAMB are characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectrum and scanning electron microscopy (SEM). Electrochemical performances of the synthesized composites are evaluated by cyclic voltammetry and galvanostatic charge/discharge measurement. All the composites with different Mn₂O₃ contents show higher specific capacitance than pure CAMB due to the pseudo-capacitance of the Mn₂O₃ particles dispersed on the surface of CAMB. The highest specific capacitance is up to 368.01 F g⁻¹ when 10 wt% Mn₂O₃ is coated on the surface of CAMB. Besides, 10%-Mn₂O₃/CAMB supercapacitor exhibits excellent cyclic stability, the specific capacitance still retains 90% of initial capacitance over 5000 cycles.