One-step electrosynthesis of MnO2/rGO nanocomposite and its enhanced electrochemical performance

We present a facile one-step electrochemical approach to generate MnO₂/rGO nanocomposite from a mixture of Mn₃O₄ and graphene oxide (GO). The electrochemical conversion of Mn₃O₄ into MnO₂ through potential cycling is expedited in the presence of GO while the GO is reduced into reduced graphene oxide (rGO). The MnO₂ nanoparticles are evenly distributed on the rGO nanosheets and act as the spacer to prevent rGO nanosheets from restacking. This unique structure provides high electroactive surface area (1173?m² g^?1) that improves ions diffusion within the MnO₂/rGO structure. As a result, the MnO₂/rGO nanocomposite exhibits high specific capacitance of 473?F?g^?1 at 0.25?A?g^?1, which is remarkably higher (3 times) than the Mn₃O₄/GO prior conversion. In addition, the electrosynthesized nanocomposite shows higher conductivity and excellent potential cycling stability of 95% at 2000 cycles.     

Vertically aligned,polypyrrole encapsulated MoS2/graphene composites for high-rate LIBs anode

Ultrathin MoS₂ nanosheets were vertically anchored on the reduced graphene oxide (MoS₂/rGO) via hydrothermal method. To further engineering the surface conductivity, ultrathin polypyrrol (PPy) layer was coated on the MoS₂/rGO composite via in situ polymerization to form a bi-continuous conductive network with a sandwich-like structure. The graphene nanosheets and the PPy coating can facilitate the electrons transfer rate, while the ultrathin MoS₂ nanosheets can enhance the utilization efficiency of the active materials. The obtained MoS₂/rGO-10 composite exhibits high reversible specific capacity (970?mAh?g^?1 at 0.1?A?g^?1) and rate capability (capacity retention of 64% at 3.2?A?g^?1). Moreover, the PPy@MoS₂/rGO hybrids reveal lower specific capacity but better rate capability, and a “trade-off” effect between electrons and ions transfer resistance was observed. This easy-scalable PPy surface conductivity engineering strategy may be applied in the preparation of high-performance LIBs active materials.     

V2O3/rGO composite as a potential anode material for lithium ion batteries

V₂O₃ is a promising anode material and has attracted the interests of researchers because of its high theoretical capacity of 1070?mAh?g^?1, low discharge potential, inexpensiveness, abundant sources, and environmental friendliness. However, the development and application of V₂O₃ have been hindered by the low conductivity and drastic volume change of V₂O₃ composites. In this work, V₂O₃/reduced graphene oxide (rGO) nanocomposites are successfully prepared through a facile solvothermal method and annealing process. In this synthesis protocol, V₂O₃ nanoparticles (NPs) are encapsulated by rGO. This unique structure enables rGO to inhibit volume changes and improve the ion and electronic conductivity of V₂O₃. In addition, V₂O₃ NPs, which exhibit sizes of 5–40?nm, are uniformly dispersed on rGO sheets without aggregation. The Li⁺ storage behavior of V₂O₃/rGO is systematically investigated in the potential range 0.01–3.0?V. The V₂O₃/rGO nanocomposite can achieve a high reversible specific capacity of 823.4?mAh?g^?1 under the current density of 0.1?A?g^?1, and 407.3 mAh g^?1 under the high current density of 4.0?A?g^?1. The results of this study provide insight into the fabrication of rGO-based functional materials with extensive applications.     

Reduced graphene oxide–gold nanoparticle membrane for water purification

The reduced graphene oxide–gold nanoparticle (rGO–Au NP) membranes are prepared by vacuum filtration method. The sizes of the Au NPs on the surface of the rGO are about 8–10 nm, and the lattice spacing of Au NPs is 0.0241 nm, which is relative to the cubic lattice of the gold crystal. The layer-by-layer stacking structure of rGO–Au NP membrane can be observed clearly by field emission scanning electron microscopy. The water flux of the rGO–Au NP membrane is as high as 204.1 L m^?2 h^?1 bar^?1, and its retention for Rhodamine B (RhB) is as high as 99.79%.     

Preparation of manganese monoxide@reduced graphene oxide nanocomposites with superior electrochemical performances for lithium-ion batteries

Manganese monoxide (MnO) nanowire@reduced graphene oxide (rGO) nanocomposites are synthesized using a simple hydrothermal method combined with a calcination process. The structural and morphological characterization of the composites indicates that the MnO nanowires homogeneously anchor on both sides of the cross-linked rGO. The nanocomposites exhibit a high surface area of 126.5?m² g^?1. When employed as an anode material for lithium-ion batteries, the nanocomposites exhibit a reversible capacity of 1195 mAh g^?1 at a current density of 0.1?A?g^?1, with a high charge-discharge efficiency of 99.2% after 150 cycles. The three-dimensional architecture of the present materials exhibits high porosity and electron conductivity, significantly shortening the diffusion path of lithium ions and accelerating their reaction with the electrolyte, which greatly improves the lithium-ion storage properties. These excellent electrochemical performances make the composite a promising electrode material for lithium-ion batteries.     

Supercapacitor device performances of polycarbazole/graphene and polycarbazole/nanoclay/graphene nanocomposites

In this study, graphene oxide (GO) is chemically reacted with sodium borohydride (NaBH₄) to form reduced graphene oxide (rGO). rGO, polycarbazole (PCz)/rGO and PCz/nanoclay/rGO materials were obtained by chemical polymerisation method. These three materials were characterised by Fourier-transform infra-red spectroscopy-attenuated transmission reflectance, scanning electron microscopy, energy-dispersive X-ray analysis, cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy. The PCz/nanoclay/rGO nanocomposite shows significantly improved capacitance (C_sp?=?187.78?F?g^?1) compared to that of PCz/rGO (C_sp?=?74.18?F?g^?1) and rGO (C_sp?=?20.78?F?g^?1) at the scan rate of 10?mV?s^?1 by CV method. The supercapacitor device performance results show high power density (P?=?1057.81?W?kg^?1) and energy density (E?=?1.7?Wh?kg^?1) obtained from Ragone plot for PCz/nanoclay/rGO material. Stability tests were also examined by the CV method for 1000 cycles.     

CoO/rGO composite prepared by a facile direct-flame approach for high-power supercapacitors

In this study, CoO nanoparticles (NPs) measuring approximately 20?nm in size are successfully grown on reduced graphene oxide (rGO) layers through a facile direct-flame approach. The obtained CoO/rGO nanocomposites are applied as electrode materials and show a high specific capacitance, reaching 1615.0?F?g^?1 at a current of 1?A?g^?1 (737.5?F?g^?1 at 50?A?g^?1), and good cycling stability (88.12% retention after more than 15,000 cycles at 5?A?g^?1), which are outstanding characteristics compared with those of recently reported pseudosupercapacitors. Furthermore, an asymmetric supercapacitor (ASC) produced using CoO/rGO as a positive electrode material and activated graphene (AG) as a negative electrode achieves a high cell voltage of 1.6?V and delivers a maximum energy density of 62.46?Wh?kg^?1 at a power density of 1600?W?kg^?1. The fabrication technique is facile and represents a promising means of obtaining metal oxide/graphene composites for high-performance supercapacitors.     

Ternary adsorbent photocatalyst hybrid (APH) nanomaterials for improved abstraction of tetracycline from water

ABSTRACT

Current health situations have instigated increased frequency of taking antibiotics for cure of infections but this amplified use is posing threats to environment. This research is focused to remove Tetracycline (TC), an antibiotic from water, using an advanced nanohybrid that compact the properties of adsorbent and photocatalyst. Compared to conventional methods for remediation of TC, large surface area (452 m²g^?1) adsorbent photocatalyst hybrid (APH) g-C₃N₄/α-MoO₃/ZIF-67 (CMZ) have found much effective as 97% degradation of TC is observed in 110 min with 0.1 g of APH. Increasing g-C₃N₄ in the hybrids has improved percent degradation of TC molecules. CMZ-3 is found as a potential candidate for water treatment.     

Hybrid H2-Selective Silica Membranes Prepared by Chemical Vapor Deposition

Hybrid organic-inorganic H₂-selective membranes consisting of single-layer or dual-layers of silica incorporating aromatic groups are deposited on a porous alumina support by chemical vapor deposition (CVD) in an inert atmosphere at high temperature. The single-layer silica membranes, which are made by the simultaneous decomposition of phenyltriethoxysilane (PTES) and tetraethylorthosilicate (TEOS), have good hydrothermal stability at high temperature and a high permeance for hydrogen in the order of 10^?7 mol m^?2 s^?1 Pa^?1 at 873 K, while preventing the passage of other larger molecular gases such as CH₄ and CO₂. The dual-layer silica membranes, which are obtained from the sequential decomposition of PTES and TEOS, exhibit an extremely high permeance for hydrogen of 3.6 × 10^?6 mol m^?2 s^?1 Pa^?1 at 873 K with a permselectivity of hydrogen over methane of 30. A normalized Knudsen based permeance method is applied to measure the pore size of PTES-derived silica membrane on the dual-layer silica membrane before treatment with TEOS. The method indicates that the pore size of the silica network is approximately in the range of 0.50–0.85 nm, which is higher than the characteristic length of pure silica membranes of 0.3 nm, accounting for the high permeance of the hybrid membranes.     

Pure and complex nanostructures using poly[bis(triiso‐propylsilylethynyl) benzodithiophene‐bis(decyltetradecyl‐thien) naphthobisthiadiazole], carbon nanotubes and reduced graphene oxide for high‐performance polymer solar cells

Crystallization of poly[bis(triiso‐propylsilylethynyl) benzodithiophene‐bis(decyltetradecyl‐thien) naphthobisthiadiazole] (PBDT‐TIPS‐DTNT‐DT) was investigated in supramolecules based on carbon nanotubes (CNTs) and reduced graphene oxide (rGO) and their grafted derivatives. The principal peaks of PBDT‐TIPS‐DTNT‐DT crystals were in the range 3.50°–3.75°. By grafting the surface of the carbonic materials, the assembling of polymer chains decreased because of hindrance of poly(3‐dodecylthiophene) (PDDT) grafts against π‐stacking. The diameters of CNT/polymer and CNT‐g‐PDDT/polymer supramolecules were 160 and 100 nm. The rGO/polymer supramolecules had the highest melting point (T_m = 282 °C) and fusion enthalpy (ΔH_m = 25.98 J g^?1), reflecting the largest crystallites and the most ordered constituents. Nano‐hybrids based on grafted rGO (276 °C and 28.26 J g^?1), CNT (275 °C and 27.32 J g^?1) and grafted CNT (268 °C and 22.17 J g^?1) were also analyzed. T_m and ΔH_m values were significantly less in corresponding melt‐grown systems. The nanostructures were incorporated in active layers of PBDT‐TIPS‐DTNT‐DT:phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) solar cells to improve the photovoltaic features. The best results were detected for PBDT‐TIPS‐DTNT‐DT:PC₇₁BM:rGO/polymer systems having J_sc = 13.11 mA cm^?2, fill factor 60% and V_oc = 0.71 V with an efficacy of 5.58%. On grafting the rGO and CNT, efficiency reductions were 12.01% (5.58%–4.91%) and 9.34% (4.07%–3.69%), respectively. © 2019 Society of Chemical Industry     

Al-doping driven electronic structure of α-NiS hollow spheres modified by rGO as high-rate electrode for quasi-solid-state capacitor

Developing an optimized electronic structure of α-NiS electrode material is critical for its high-rate electrochemical performance of quasi-solid-state capacitor. Herein, Al³⁺ have been doped into α-NiS lattice and the reduced graphene oxide (rGO) is employed to modify Al-doping α-NiS, to alleviate the low-mobility charge of α-NiS. The electronic structure and electrochemical properties of α-NiS hollow spheres induced by Al-doping and rGO modification are investigated, both experimental characterization and theoretical results confirm Al-doping affect the electronic structure and electrochemical performance of α-NiS hollow spheres. In the composite of Al-doping α-NiS and rGO (named as Al_xNi_1-xS/rGO), the doped heteroatom improves the intrinsic electronic structure of α-NiS and the rGO provides a good electric conducting network, leading to an enhanced electrochemical performance of α-NiS as high-rate electrode material. After evaluation, the optimized Al_0.2Ni_0.8S/rGO composite shows a superior reversible capacity of 1096 C g^?1 at 2 A g^?1, and retains a capability of 471 C g^?1 at a high-rate of 30 A g^?1. Moreover, an asymmetric quasi-solid-state hybrid capacitors assembled by Al_0.2Ni_0.8S/rGO and activated carbon presents a high energy density of 30.6 Wh kg^?1. This work provides a foundational strategy for the modification of α-NiS through Al-doping and combining with rGO, which has a positive effect on α-NiS electrode material in quasi-solid-state hybrid capacitors.     

In-situ synthesis of reduced graphene oxide wrapped Mn3O4 nanocomposite as anode materials for high-performance lithium-ion batteries

We report a novel in-situ symbiosis method to prepare reduced graphene oxide wrapped Mn₃O₄ nanoparticles (rGO/Mn₃O₄) with uniform size about 50 nm as anodes for lithium-ion batteries (LIBs), which can simplify the preparation process and effectively reduce pollution. The rGO/Mn₃O₄ nanocomposite exhibited a reversible specific capacity of 795.5 mAh g^?1 at 100 mA g^?1 after 200 cycles (capacity retention: 87.4%), which benefits from the unique structural advantages and the synergistic effect of rGO and Mn₃O₄. The Mn₃O₄ nanoparticles encapsulated among the rGO nanosheets exhibited good electrochemical activity, and the multilayer wrinkled rGO sheets provided a stable 3D conduction channel for Li⁺/e^? transport. The rGO/Mn₃O₄ nanocomposite is a promising anode candidate for advanced LIBs with excellent cycling performance and rate performance. Furthermore, this new preparation method can be extended to green and economical synthesis of advanced graphene/manganese-based nanocomposites.     

Solid polymer electrolytes. XI. Preparation,characterization and ionic conductivity of new plasticized polymer electrolytes based on chemical‐covalent polyether–siloxane hybrids

A new hybrid polymer electrolyte system based on chemical‐covalent polyether and siloxane phases is designed and prepared via the sol–gel approach and epoxide crosslinking. FT‐IR, ¹³C solid‐state NMR, and thermal analysis (differential scanning calorimetry (DSC) and TGA) are used to characterize the structure of these hybrids. These hybrid films are immersed into the liquid electrolyte (1M LiClO₄/propylene carbonate) to form plasticized polymer electrolytes. The effects of hybrid composition, liquid electrolyte content, and temperature on the ionic conductivity of hybrid electrolytes are investigated and discussed. DSC traces demonstrate the presence of two second‐order transitions for all the samples and show a significant change in the thermal events with the amount of absorbed LiClO₄/PC content. TGA results indicate these hybrid networks with excellent thermal stability. The EDS‐0.5 sample with a 75 wt % liquid electrolyte exhibits the ionic conductivity of 5.3 × 10^?3 S cm^?1 at 95°C and 1.4 × 10^?3 S cm^?1 at 15°C, in which the film shows homogenous and good mechanical strength as well as good chemical stability. In the plot of ionic conductivity and composition for these hybrids containing 45 wt % liquid electrolyte, the conductivity shows a maximum value corresponding to the sample with the weight ratio of GPTMS/PEGDE of 0.1. These obtained results are correlated and used to interpret the ion conduction behavior within the hybrid networks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1000–1007, 2006     

Tape casting of polysiloxane-derived ceramic with controlled porosity and surface properties

Tape casting has been applied to produce porous hybrid and SiOC ceramic tapes using ceramic precursors and commercially available polysiloxanes as polymeric binders. SiC particles of two different mean sizes (4.5 or 6.5?μm) were used as inert fillers to prevent shrinkage and increase mechanical stability. Macroporosity was adjusted by varying the azodicarbonamide (ADA) content from 0 to 30?wt.%. Decomposition of the polysiloxanes at 600?°C resulted in the generation of micropores with high specific surface area (187–267 m²?g^?1) and a predominant hydrophobic behavior. At 1000?°C mainly meso/macroporosity were observed (SSA: 32–162 m²?g^?1) accompanied by increased hydrophilicity. The influence of ADA content, SiC size, and pyrolysis temperature on open porosity (2.5–37%), average pore size (<0.01–1.76?μm), surface characteristics, and flexural strength (10.5–121?MPa) were investigated. The porous tapes with different surface characteristics and controlled structure are highly promising for applications involving membrane processes, particularly microfiltration systems (0.1–10?μm).     

Polyamide-silica gel hybrids containing metal salts: Preparation via the sol-gel reaction

The hydrolysis and condensation of tetramethoxysilane in a DMF solution of polyamides containing LiCl, CaCl₂ or ZnCl₂, both in presence and absence of polyoxazoline, resulted in the facile formation of polyamide-silica gel hybrids. Films were cast from the resulting mixtures and evaporation of the solvent resulted in the formation of clear, transparent hybrids with the salts dispersed at the molecular level. Pyrolysis of hybrids at 600 °C gave porous silica. Pore size and surface characteristics of these silica gel samples indicated a porous nature with a pore radius of 1.1 nm for silica gels obtained from hybrids HPA-6 (containing no salt) and HPA-9 (containing ZnCl₂) and a surface area of 213 m² g⁻¹ and 310 m² g⁻¹, respectively. Silica gel from hybrid HPA-7 (containing LiCl) had a pore radius of 1.9 nm and a surface area of 15 m² g⁻¹. The silica gel samples obtained from hybrids HPA-6, HPA-7 and HPA-9 exhibited narrow slit-like pores with a pore volume of 0.68 cm³ g⁻¹. Received: 7 January 1997/Accepted: 6 March 1997     

Thermal,thermomechanical, and electrochemical characterization of the organic–inorganic hybrids poly(ethylene oxide) (PEO)–silica and PEO–silica–LiClO4

To study the effect of the silica content on the properties of the salt‐free and salt‐added hybrids based on poly(ethylene oxide) (PEO) and silica, two series of hybrids, PEO–silica and PEO–silica–LiClO₄ (O:Li, 9:1) hybrids were prepared via the in situ acid‐catalyzed sol–gel reactions of the precursors [i.e., PEO functionalized with triethoxysilane and tetraethyl orthosilicate (TEOS)]. The morphology of the hybrids was examined by scanning electron microscopy (SEM) of the fracture surfaces of the hybrid. The results indicated that the discontinuity develops with increasing the weight percent of silica in both hybrids. The differential scanning calorimetric (DSC) analysis indicated that effects of silica content on the glass transition temperatures (T_g) of the PEO phase were different in salt‐free and salt‐added hybrids. The T_g of PEO phase increased with increasing weight percent of silica in salt‐free hybrids, whereas the curve of T_g of PEO phase and silica content had a maximum at 35 wt % of silica content in salt‐added hybrids. For both salt‐free and salt‐added hybrids, peaks of the loss tangent, determined by dynamic mechanical analysis (DMA) were gradually broadened and lowered with increasing weight percent of silica. The storage modulus, E′, in the region above T_g increases with increasing silica content for both PEO–silica and PEO–silica–LiClO₄ hybrids. In the conductivity and composition curves for PEO–silica–LiClO₄ hybrids, the conductivity shows a maximum value of 3.7 × 10^?6 S/cm, corresponding to the sample with a 35 wt % of silica. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2471–2479, 2001     

Al2O3–Ag nanopowders: new method of synthesis,characterisation and biocidal activity

Abstract

Abstract

The present paper describes an innovative method of producing silver nanoparticles incorporated into an aluminium nano‐oxide substrate. The method utilises thermal decomposition and reduction, which yields an Al₂O₃–Ag nanopowder with the average size of particles ranging from 43 to 60?nm and the average size of agglomerates between 330 and 870?nm. The average size of the silver nanoparticles incorporated in the aluminium nano‐oxide carrier ranges from 22 to 60?nm. The Al₂O₃–Ag nanopowders thus produced have a largely developed surface area (above 200?m²?g^?1) with a great number of open pores (above 5×10^?4?m³?g^?1), which gives evidence that their tendency to agglomeration is only slight and that the possible agglomerates have a loose structure. Moreover, the nanopowders show good bactericidal and fungicidal properties. The results obtained in the present experiments show that the Al₂O₃–Ag nanopowders produced by the proposed method can be used successfully as the raw material in the production of biocidal biomaterials.     

Li0.95Na0.05MnPO4/C nanoparticles compounded with reduced graphene oxide sheets for superior lithium ion battery cathode performance

Sodium-substituted LiMnPO₄/C/reduced graphene oxide (LNMP@rGO) was synthesized in this study via freeze drying and carbon thermal reduction method with graphene oxide as carbon source. Sodium ion doping is optimized and rGO effects are evaluated by XRD, SEM, TEM, BET, Raman, and electrochemical performance measurements. Well-distributed nanoparticles with average size of ~50?nm are evenly distributed on the surface or intercalation between rGO layers, resulting in a porous ion/electronic conductive network. Compared to 122.3?mA?h?g^?1 in unmodified LNMP, the best LNMP@rGO (20?mg rGO) exhibits an excellent initial discharge capacity of 150.4?mA?h?g^?1 at 0.05?C at 122.9% of the initial capacity. The capacity retention rate is 95.8% of the initial capacity after 100 cycles at 1?C. Capacity of 101.2?mA?h?g^?1 is preserved even at rates as high as 10?C.     

YSZ/MoS2 self-lubricating coating fabricated by thermal spraying and hydrothermal reaction

Thermal sprayed ceramic coatings have extensively been used in components to protect them against friction and wear. However, the poor lubricating ability severely limits their application. Herein, yttria-stabilized zirconia (YSZ)/MoS₂ composite coatings were successfully fabricated on steel substrate with the combination of thermal spraying technology and hydrothermal reaction. Results show that the synthetic MoS₂ powders are composed of numbers of ultra-thin sheets (about 7 ~ 8?nm), and the sheet has obvious lamellar structure. After vacuum impregnation and hydrothermal reaction, numbers of MoS₂ powders, look like flowers, generate inside the plasma sprayed YSZ coating. Moreover, the growing point of the MoS₂ flower is the intrinsic micro-pores of YSZ coating. The friction and wear tests under high vacuum environment indicate that the composite coating has an extremely long lifetime (>?100,000 cycles) and possesses a low friction coefficient less than 0.1, which is lower by about 0.15 times than that of YSZ coating. Meanwhile, the composite shows an extremely low wear rate (2.30?×?10^?7 mm³ N^?1 m^?1) and causes slight wear damage to the counterpart. The excellent lubricant and wear-resistant ability are attributed to the formation of MoS₂ transfer films and the ultra-smooth of the worn surfaces of hybrid coatings.     

Mechanical and thermal properties of h-BN based composite containing dual glass phases at elevated temperatures

High-temperature mechanical and thermal properties of h-BN based composite containing amorphous silica and Yb-riched silicate glass phases were systematically investigated in this work. Owing to anisotropic microstructure of h-BN matrix, the obtained composite demonstrates anisotropic mechanical and thermal properties. The composite possesses higher elastic modulus at 1673?K than that at room temperature and presents excellent high-temperature stiffness. Flexural strengths in parallel and perpendicular directions reach 496?±?22 and 258?±?21?MPa at?1073?K, respectively, and increases by 74 and 66% compared with the room-temperature strengths of 285?±?4?and 155?±?5?MPa. The composite containing dual glass phases shows lower coefficients of thermal expansion in the temperature range of 473–900?K, the values are ?1.4?×?10^?6 and 0.3?×?10^?6 ?K^?1 for the perpendicular and parallel directions, respectively. Thermal conductivities in the perpendicular and parallel directions at 373?K are 24.8 and 14.8?W?m^?1?K^?1, respectively, and then decrease to 14.9 and 9.3?W?m^?1?K^?1 at 1473?K.