Search

Graphene paper is a promising electrode material for use in flexible supercapacitors due to its good electronic conductivity and excellent mechanical characteristics. However, layers of graphene paper have a strong tendency to restack, resulting in a seriously reduced specific surface area and limited electrochemical performance. In this paper, restacked layers of graphene paper are reopened by a vacuum-assisted method, and carbon nanotubes (CNTs) are directly deposited on the enlarged space between the opened graphene layers. Consequently, an ordered carbon composite structure with alternately arranged graphene sheets and CNTs is constructed and exhibits increased specific surface area and a 3D conductive network. The structure and morphology of the samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy and N2 adsorption/desorption measurements. The electrochemical performance was tested by galvanostatic charge-discharge test (GDC), electrochemical impedance spectroscopy (EIS) and cyclic voltammograms (CV). The obtained graphene/CNT paper exhibits a remarkably improved capacity of 170.8 F g−1, which is nearly two times higher than that obtained for a regular graphene paper.

Hybrid Sn–Co binary oxide with different Sn/Co feeding molar ratios on carbon paper are successfully obtained using a facile hydrothermal method followed by a post-annealing procedure. The results of electrochemical tests show that the electrode with a feeding molar ratio of 1:4 (named as Sn1Co4) has better electrochemical performance than that of the others. The specific capacitance can achieve 937.4 F g−1at 5 mV s−1 (580.8 F g−1 at 1 A g−1), as well as the capacitance retention is 97.5% after the galvanostatic charge-discharge for 20000 cycles at 30 A g−1. These results demonstrate that the Sn1Co4 can be considered as a potential electrode material for the next generation supercapacitor.

A novel and one-pot calcination method is applied for the fabrication of SnS nanoparticles coated by ultrathin carbon layer on carbon paper, resulting in a SnS/C-carbon paper free-standing electrode for lithium ion batteries. In this hierarchical structure, the carbon layer has dual function of buffering the volume change of SnS and anchoring SnS nanoparticles on the substrate compactly. Besides, it also can boost charge transfer kinetic in the electrode. Meanwhile, the carbon paper with three-dimensional structure allows for fully absorption of electrolyte and provides efficient transport pathways for electrons. Benefiting from these structure features, the binder-free SnS/C-carbon paper electrode exhibits excellent cyclability and delivers a reversible capacity of 696.2 mAh g−1 at a current density of 0.5 A g−1 after 200 cycles. Besides, SnS/C-carbon paper free-standing electrode achieves a reversible capacity of 562.3 mAh g−1 at a current density of 2.0 A g−1, demonstrating a promising rate ability which is significant for high power applicants. Such one-pot and novel route to synthesize SnS/C-carbon paper free-standing electrode with excellent electrochemical performance can pave the way for the development of low-cost and time-saving fabrication of free-standing anode for high-performance lithium ion batteries.

Mn3O4 nanoparticles were anchored on the surface of oxidised graphite paper via template-free hydrothermal method. Synthesized samples were characterized using different techniques such as X-ray diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HRTEM) and X-ray Photoelectron Spectroscopy (XPS). Electrochemical capacitor behaviour was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The binder free material was found to exhibit a specific capacitance of 471 F g−1 at a current density of 1 mA cm−2 in 1 M Na2SO4. Conductive additive free, Mn3O4 anchored electrode was used as positive electrode in the asymmetric cell fabrication; the asymmetric cell was tested at a potential window of 1.6 V and its performance characteristics were evaluated. The asymmetric cell delivered a maximum specific energy of 47 Wh kg−1 at a power density of 202.5 W kg−1 which evidenced the superior performance of the synthesized electrode material. Here in the present work, the surface oxidised graphite paper was used as an excellent current collector and active sites for anchoring Mn3O4 due to its desirable properties.

α-Fe2O3 nanoparticles/multi-wall carbon nanotubes (MWCNTs) hybrids were successfully prepared via a facile one-step hydrothermal method. The MWCNTs enhances the conductivity and provides space for stress and strain during volume expansion of α-Fe2O3 semiconductor as the anode for LIBs. The composite shows impressive electrochemical performance when it was used as the electrodes of coin cells. The α-Fe2O3 electrode with 50 wt% MWCNTs retains its capacity of 816.8 mAh g−1 after 50 cycles at the current density of 200 mA g−1, which is superior to those of contrast samples (bare α-Fe2O3, pure MWCNTs, 10 wt%, 30 wt%, 70 wt% MWCNT/α-Fe2O3 hybrids). Furthermore, the flexible carbon nanofiber paper (CNP) has also been investigated as a novel current collector with lithium storage for application in LIBs, and the capacity of free-standing α-Fe2O3/50 wt%MWCNTs/CNP hybrids electrode can retain 467.2 mAh g−1 after 50 cycles under the current density of changes from 2500 mA g−1 to 200 mA g−1. The MWCNTs improved cycle performance, enhanced reversible capacities and rate capability of MWCNTs/α-Fe2O3 anodes can attribute to the inherent conducting network, shorten electron pathway and faster reaction kinetics.

The electrode materials with large surface area and high porosity are predominant to enable the energy storage properties of electrochemical supercapacitors. Herein, lab-waste tissue paper templated trimanganese tetroxide hollow microtubes (Mn3O4 HMTs) with high porosity on their walls were synthesized via a facile biomorphic method. Initially, aqueous manganese precursor was impregnated onto the surface of cellulose fibers by means of evaporation of water molecules. After thermal treatment under ambient atmosphere, the cellulose fibers were removed, which led to the formation of Mn3O4 HMTs. The morphology, crystallinity and surface area of the prepared Mn3O4 HMTs were examined by FE-SEM, XRD and BET analyses. When tested in aqueous alkaline electrolyte, the as-prepared Mn3O4 HMTs delivered a maximum specific capacitance of 51.7 F g−1 at the current density of 1 mA cm−2 with good rate capability of 64.6% at high current density of 10 mA cm−2, which is due to the high porosity that enables an effective penetration of electrolyte ions. After 2000 cycles, the porous Mn3O4 HMTs demonstrated good cycling stability of 57.1% at a current density of 5 mA cm−2. This facile method for the preparation of hollow structured materials could provide a deep insight into novel pseudocapacitive materials.

A facile one-step solid-phase synthesis strategy is developed for synthesizing a binder-free molybdenum disulfide/carbon fibers paper (MoS2/CFP) anode. The microstructure, composition, morphology and electrochemical performances were investigated. It is found that the thin MoS2 layers are well anchored on the interlaced carbon fibers to form MoS2/CFP, which has mesoporous structure and large specific surface area of ∼18.8 m2g-1. As a result, the obtained MoS2/CFP anode exhibits a reversible capacity of 261 mAh·g−1 with 31.2% loading ratio of MoS2. After subtracting the capacity of CFP, the MoS2 in the composite anode delivers a reversible capacity of 539 mAh·g−1 and shows better cycle stability than commercial MoS2 after 100 cycles at 100 mA g−1. The remarkable electrochemical performances could be attributed to the buffer space among carbon fibers for the volume changes of MoS2 as well as the highly conductive carbon fibers network, suggesting that the MoS2/CFP is a promising binder-free anode for lithium-ion batteries.

Lithium sulfur batteries have been regarded as next-generation battery technology due to its high energy density, environmental benignity and abundance. However, the poor electric/ionic conductivity of sulfur limits the practical use of sulfur in an electrode. The main problem is the high solubility of long-chain polysulfides, which are the intermediates of the electrochemical processes in the liquid electrolyte. The dissolved polysulfide ions shuttle between the cathode and anode, thus causing precipitation of insulating Li 2 S 2 /Li 2 S on the surface of the electrode. The unavoidable phenomenon results in loss of active materials and fast capacity fading. In this regard, we show one simple method to prepare free-standing paper electrode used as cathode material for lithium sulfur batteries. Binder-free graphene-polypyrrole (PPy)/S-graphene (G-PPy/S-G) paper-like sandwich structural electrode was prepared by using the vacuum filtration method. In this structure, the unique graphene layers of sandwich-like framework not only serve as a conductive film, but also effectively block the diffusion of polysulfides, leading to suppression of the shuttle effect and low self-discharge behaviour. In addition, the middle layer, the PPy nanofibers can limit the diffusion of dissolved polysulfides due to the special bond with sulfur, and furthermore maintain the structural stability of the paper electrode because the nanofibers can serve as elastic springs to accommodate the huge volume changes in charging-discharging processes. When tested as cathode for Li-S batteries, the as-prepared sample G-PPy/S-G exhibits excellent electrochemical performance. We believe that our strategy could provide a useful pathway towards commercial utilizing of sulfur.

One key challenge in flexible batteries lies in the development of deformable/flexible electrode with high active materials mass loading and good electronic conductivity. Herein, we report such a paper-like TiO2/graphene-carbon nanotube hybrid electrode by a facile vacuum filtration approach. In this electrode, titania nanoparticles with uniform size (9 nm) and carbon nanotubes are embedded into graphene sheet homogeneously, forming a peculiar 3D conducting network. This feature ensures 1) a high TiO2 mass loading (77.3 wt %, 2.93 mg cm−2); 2) good electric conductivity (∼1000 S m−1); and 3) good flexibility. Benefiting from these, the electrode delivers a high specific capacity (214 mAh g−1), excellent rate capability, and up to 700 cycles stability at a high rate of 1000 mA g−1. This fabrication strategy demonstrates great practical potential and opens up new idea for high-performance self-supported electrode design.

Flexible all-solid-state supercapacitors (FASSCs) have attracted much attention as power supplies for portable and wearable electronic products. Herein, we report the fabrication of a foldable, extra lightweight, flexible chopped carbon fiber paper (CFP) with a porous network structure prepared via wet-mold papermaking that can serve as a conductive substrate. The conductivity and pseudocapacitance of the electrode were improved by controlling the growth of 3D Cu(OH)2 nanorod arrays on CFP substrate. The Cu(OH)2@CFP electrode has a high specific capacitance of 421.8 mF cm−2 at a current density of 0.5 mA cm−2 with capacitance retention of 82.98% at a current density of 10 mA cm−2 after 5000 charge-discharge cycles. The FASSC manifested not only a large capacitance of 196.1 mF cm−2 at 2 mA cm−2, as well as energy and power densities of 6.97 × 10−2 mWh cm−2 and 1.6 mW cm−2, respectively, but also excellent stability of 80.3% over 5000 cycles at 5 mA cm−2. In addition, we confirmed that the FASSC has a large bending angle and can be twisted into various shapes, thereby indicating its applicability in portable and wearable electronic devices.

Cobalt-based nanomaterials have received considerable attention in electric energy-storage devices due to their outstanding electrochemical characteristics. However, multiple time- and energy-consuming steps and complex reduction processes for producing cobalt and cobalt oxide nanostructures are disrupting their substantive commercialization. Here, we propose a facile, ultra-fast, and versatile method for the fabrication of cobalt and cobalt oxide nanostructures using an intense pulsed white light (IPWL) photothermal reduction technique. The mechanism of the IPWL photothermal reduction of cobalt and cobalt oxide is firstly studied by measuring the in-situ temperature of the Co(NO3)2-coated carbon fiber paper (CFP) substrate during IPWL irradiation and analyzing the crystal structures of the IPWL-irradiated samples. Cobalt nanoflakes and cobalt oxide nanoparticles are synthesized on the surface of the CFP substrate by irradiating IPWL for 10 ms at ambient temperature and pressure with various energy densities from 10 to 30 J cm−2. The Co3O4 nanoparticle/CFP and Co nanoflake/CFP samples are further utilized as an electrode, and each electrode exhibits high specific capacity of 29 and 73 mA h g−1, respectively, at a current density of 1 A g−1. Since this novel photothermal reduction technique is applicable to other transition metals and metal oxides, it is a promising method for not only energy storage systems, but also for energy generation applications, filters, sensors, and catalysis systems.

Paper-based sensing platforms have become one of the hot topics in spectroscopic technique for chemical and biological detections. However, it has been still challenging to detect molecules at trace levels owing to its intrinsic interconnected porous structures related to the fibril structure of paper and hydrophilic characteristic. Herein, a cellulose paper combined molecular polymers and hybridized chain reaction that led to hydrophobic functionalization with static water contact angles>90° for surface-enhanced Raman scattering (SERS) was proposed. During the fabrication, the formation of the ultrasensitive SERS is supported by interconnection of silver nanoparticles (NPs) of varying diameters from 20 to 50 nm and concentration in the range of 2–6 mL on one side of the paper substrate to achieve excellent quantification capability based on hotspots engineering-based clusters and analyte enrichment system, particularly, AgNPs with diameter of 30 nm exhibit the highest Raman signals at 532 nm excitation. The resulting plasmonic arrays show SERS detection of CV molecules at a low concentration of 10–10 M with an enhancement factor of 1.2 × 108 and excellent reproducibility with RSD of Raman signal as low as 10.39%. An outstanding selectivity each probe molecule in an analyte mixture solution of R6G and CV at diluted concentration (10−8 M) of the platform was obtained. These outcomes could be designated to the more target molecules trapped in the hotspots and cluster of AgNPs after activated molecular enrichment mechanism underlying hydrophobic layer correlated with natural evaporation.

Ni100−xFex alloy catalysts are prepared as an alternative to Pt-based catalysts for the hydrogen evolution reaction (HER) in water electrolysis. For optimum bonding and adhesion stability between a carbon paper (CP) electrode and Ni100−xFex alloy particles, the latter (obtained by varying the Ni/Fe ratio) is directly grown onto the CP electrode hydrothermally. The shape, crystallinity, and electrochemical properties of the alloy particles were analyzed using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and linear sweep voltammetry (LSV). Raman spectroscopy identifies that very few crystal defects are generated in the Ni100−xFex alloy catalyst during the HER, resulting in a significant improvement in the alloy's electrocatalytic performance. The XPS alloy catalyst profiles before and after the HER reveal water is easily adsorbed on the Fe2+ component, and more H2 is generated on the Ni0 component. The optimum Ni90Fe10/CP catalyst electrode exhibits an overpotential of − 0.244 V (η = 246 mV) and a Tafel slope of 95.4 mV dec−1 at 100 mA cm−2 in a 1.0 M KOH electrolyte. Moreover, the electrode shows a Faradaic efficiency of 97.07% and excellent catalytic activity over 10 days and after 3000 LSV cycles.

Wrinkled-paper-like ZnCo2O4 nanoflakes were synthesized by a facile hydrothermal synthesis and a post-annealing treatment. As an anode for lithium-ion batteries, it exhibits high capacity, excellent cyclability and ultrahigh rate performance. A reversible capacity of 1138 mAh g(-1) at 1 A g(-1) was obtained after 500 cycles. After cycled at current densities from 0.2 to 25.6 A g(-1), the reversible capacity can recover to 1089 mAh g(-1) at 0.2 A g(-1). It has been demonstrated that the wrinkled-paper-like ZnCo2O4 nanoflakes are promising for application as future energy storage units. (C) 2017 Elsevier B.V. All rights reserved.

Magnetic paper manufactures are nowadays widely used in information storage, electromagnetic shielding and security industry for its outstanding performances. In this article, Tb-doped germanium borosilicate glass was prepared by melt quenching technique and they were used as magnetic sources of magnetic paper to loading into the bamboo fibers. Magnetic paper has been successfully produced by adding inorganic magnetic particles modified by different concentrations of graphene oxide (GO) solution. The samples were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, Superconducting Quantum Interferometer Device (SQUID) and Scanning Electron Microscope (SEM). The results shown that the structure of magnetic particle are made from [BO3], [BO4], [A1O6], [SiO4] and [GeO4]. GO sheets had been successfully immobilized on magnetic particles (MPs) surface via electrostatic interaction. SQUID indicated that the magnetic particles and papers were paramagnetic materials. SEM images clearly shown that the MPs loaded into the lumen of bamboo fibers and the interstitial of fibers. Bridge-fibers that connecting other cellulose fibers and MPs by hydrogen bonds were formed in the network of paper due to the functional groups on surface of magnetic particles. The mechanical properties of papers increased with the increment of GO concentration, which is correlated with the hydrogen-bonding that forming by bridge-fibers and other cellulose fibers in network of paper.

We report here the rational development of MnO2 nanorods coated tea bag filter paper (TBFP) as a self-standing, bendable, and disposable electrochemical probe for the sensitive and selective H2O2 detection and addresses their challenges in H2O2 sensing via the replacement of ‘O’ with ‘S’ in the form of MnS microcubes and its core@shell architecture with MoS2. The as-configured MnS@MoS2/TBFP overwhelms the constrains of conventional electrochemical probes including time and cost consumed electrode surface renewability and catalyst loading progression, and the practice of an insulating binder. The hierarchical open porous architectures of MoS2-shell favour the diffusion of H2O2 into the core-MnS microcubes, facilitating an analyte utilization efficacy at both the core and shell architectures. The impacts of core@shell morphological features, replacement of ‘O’ with ‘S’, surface defects, and lattice distribution of MnS@MoS2 toward non-enzymatic H2O2 sensing performances are elucidated using variant electrochemical techniques. With the synergism of uniformly implanted and exposed metallic active sites, efficient electron transfer rate, and high analyte utilization efficiency, MnS@MoS2/TBFP exposes the low detection limit (120 nM), excellent sensitivity (650 μA mM−1 cm−2), and wide linear range (500 nM-5 mM) on H2O2 detection. Furthermore, the scrutinized non-enzymatic H2O2 detection concerts of MnS/MoS2/TBFP are selective, decisive, repeatable, and stable, constructing the excellent recovery rates in human urine sample analyses. Thus, the collective benefits of free-standing, flexible, binder-less, re-functional, and cost-efficient MnS@MoS2/TBFP probe actualize the evolution of affordable and high performance H2O2 sensors.

High-performance N-doped carbon quantum dots (NCQDs) were synthesized by a proposed green route based on hydrothermal treatments using waste paper and urea as C and N sources. The single-crystalline NCQDs demonstrated strong blue-green luminescence with the maximum intensity enhancement of 6.5 times when compared with undoped CQDs under UV and visible light excitations. XPS spectra results suggested that the enhanced photoluminescence might be attributed to pyridinic N, which could be controlled by adjusting hydrothermal temperature, time, and urea concentration. The NCQDs having excellent optoelectronic properties were fabricated into broadband photodetectors by incorporating ZnO nanorod arrays. Owing to the NCQDs, the detectors demonstrated broadband photoresponse with significantly enhanced photoresponsivity, faster response, and better sensitivity in visible range. The work provides a low-cost, environment friendly route to fabricate excellent NCQD-based broadband photodetectors for various technological applications.

In this work, a lightweight and efficient supercapacitor on a flexible paper has been developed. Flexible electrodes of bismuth ferrite (BFO)/graphene nanocomposite have been fabricated by a simple drop casting method. The mechanical stability of the electrodes was tested by bending the supercapacitor. The BFO/graphene electrode with its porous structure has more electrolyte accessibility and the graphene nanosheets act as an effective conductive pathway for charge transportation between the electrode material and the current collector. The electrode exhibited excellent electrochemical performance in terms of specific capacitance and cycle stability. The electrode demonstrated specific capacitance of 9 mF/cm2determined from cyclic voltammetry test at a scan rate of 10 mV/s in the potential window of 0–0.9 V. It can deliver specific power of 0.5–3.5 kW/kg with moderate energy density. The electrode retains 98% capacitance over 1000 cycles and 95% after 5000 cycles. The BFO/graphene nanocomposite electrode demonstrated good mechanical stability towards flexible supercapacitor application. X-ray diffraction, Raman spectroscopy, and field emission scanning electron microscopic analyses revealed the formation of BFO/graphene nanocomposite. The electrochemical results such as cyclic voltammetry and galvanostatic charging/discharging suggested that BFO/graphene nanocomposite electrode has a significant potential for flexible energy storage system.

A novel electrode consisting of 3D porous nickel‒cobalt‒copper sulfide dendritic structures is synthesized, in which, for the first time ternary Ni–Co–Cu foam is constructed through hydrogen bubble template and followed by sulfidization via a hydrothermal reaction in thiourea. The 3D, porous Ni–Co–Cu dendritic sulfide electrode exhibits a high specific capacitance of 1203.75 F g−1 (0.963 F cm−2) at current of 1.0 mA and excellent cycling stability, excellent ratability along with high cycle stability. An asymmetric supercapacitor (ASC) using dendritic sulfide structures and reduced electro-etched carbon fiber paper (RECF) as the positive and negative electrodes, respectively is developed. RECF is prepared through electrochemical oxidation process in acidic solution followed by electrochemical reduction, which exhibits a high areal capacitance of 695 mF cm−2 at current of 1.0 mA. The assembled device can be operating reversibly between 0 and 1.6 V and provides high specific capacitance of 178.5 mF cm−2 and an excellent cycling stability of 97.3% after 1000 cycles. This work exploits a pathway to construction of dendritic sulfides of quaternary metal foams that could be used for any flat metal substrate and open a new doorway to quaternary transition metal sulfides electrode materials in energy storage and conversion devices.

Ti3C2Tx is promising negative electrode materials for asymmetric supercapacitor (ASC). The Ti3C2Tx sheets are obtained by etching Ti3AlC2 powders in the mixture solution of HCl and LiF, then vacuum filtrated to achieve a free-standing Ti3C2Tx-paper. The electrochemical performance of Ti3C2Tx-paper was measured and a high volumetric capacitance of 295.4 F cm−3 was achieved. Meanwhile, it exhibited a high capability rate of 79.7% from 2 mV s−1 to 100 mV s−1 and long cycle life with 94.4% retention of its initial after charged and discharged for 15000 cycles at a current density of 10 A g−1. ASC devices were fabricated using Ti3C2Tx-paper as negative electrode and carbonized filter paper as positive electrode. The energy density and power density of ASC device are 4.5 Wh kg−1 and 1.3 kW kg−1, respectively. The application of the device has been demonstrated by lighting red light emitting diode, endowing prospect of the Ti3C2Tx-paper as negative electrode for supercapacitors.

In this work, a facile method to prepare graphene oxide films with controllable interlayer distances similar to that of wet-spinning is proposed. Wet graphene oxide gel films were dipped into coagulation bath for crosslinking. Calcium chloride, two ionic liquids, 1-butyl-3-methylimidazole L lactate and 1-aminopropyl-3-methylimidazolium chloride and 1,8-octanediamine were chosen as the coagulants. The obtained graphene oxide films were characterized by Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, X-ray diffraction and tensile tests. The adsorption of Rhodamine B solutions tests proved that GO films with different interlayer distances exhibited varied sieving performance.

In this study, 3D titanium dioxide-reduced graphene oxide aerogels (TiO2-rGA) was synthesized by a modified hydrothermal treatment. Graphene is self-assembled into the 3D interconnected networks aerogel while TiO2 nanoparticles are uniformly and densely dispersed onto the graphene nanosheets. The as-obtained composite aerogels show a change of surface wettability from hydrophobic to hydrophilic depending on addition of incorporated TiO2. Absorption abilities of TiO2-rGA with different ratios of TiO2 for Oleic acid and RhodamineB (RhB) dye were tested. The result demonstrates that the composite aerogel with addition ratio of TiO2 can selectively absorb oleic acid floating on the water and RhB in aqueous systems. The resulting TiO2-rGA can be potentially applied in organic waste recovery.

A facile and scalable method for deposition of nano metals in multi-layer graphene is developed. Nano Sn-graphene hybrid (Sn@Gr) is prepared for high performance anode in lithium ion battery, via the in-situ deposition of Sn nanoparticles in multi-layer graphene through pyrolysis of glucose and tin chloride in molten salts with addition of ammonium chloride. The synthesized Sn@Gr demonstrates a lithiation capability (1000 mAh g−1 of Sn@Gr) higher than the dual lithiation capacity from graphite and Sn. The in-situ formed Sn nanoparticles not only expand the interlayer space of the multi-layer graphene to increase the lithiation capacity of graphene but also bridge the graphene sheets to enhance the electrical conduction in longitudinal direction of graphene sheet, leading to the excellent rate performance. The mechanical toughness of the graphene coupled with the firm connection between nano-Sn and graphene sheet contributes the enhanced durability of the Sn@Gr anode. Both lithiation and delithiation capacities of 671 mAh g−1 remain even after 700 cycles at a current of 800 mA g−1. A stable rate capacity as high as 606 mAh g−1 has been achieved at a current of 1000 mA g−1.

A three-dimensional (3D) graphene/Ni 3 S 2 nanostructure grown on nickel foam using a one-step chemical vapor deposition process is an excellent template for the synthesis of graphene-based composite electrodes for use in supercapacitors. The as-grown graphene/Ni 3 S 2 nano-structures have high crystalline quality and surface area. Electrochemical characterization shows that the 3D porous graphene/Ni 3 S 2 electrode exhibits a high specific capacitance of 741 F/g at 1 mV/s, with 92.3% of the specific capacitance retained after 5000 charging-discharging cycles. Such high performance of a 3D graphene electrode can enrich the prospects for future practical applications in energy storage.

We report a new method for few-layer graphene (FLG) preparation via plasma-assisted ball milling with carbide, nitride or oxides as ball-milling media and expandable graphite raw material. Scanning electron microscopy, transmission electron microscopy and Raman spectroscopy were applied to characterize the FLG. FLGs prepared by using different ball-milling media such as boron nitride (BN), tungsten carbide (WC), zinc oxide (ZnO), iron oxide (Fe2O3) and germanium oxide (GeO2) were used to determine the relationship between the FLG layer number and inductive capacity of the ball-milling media. Parameters for the synthesis of high-quality FLGs were also optimized.

Strongly coupled FeP@reduced graphene oxide (FeP@rGO) nanocomposites are synthesized by low-temperature phosphorization of α-FeOOH@graphene oxide (α-FeOOH@GO). The introduced graphene sheets not only effectively buffer the volume change during lithiation/delithiation, but also largely facilitate the ionic/electron diffusion kinetics. When used as anode materials for lithium-ion batteries (LIBs), FeP@rGO nanocomposites show excellent electrochemical performance. Among them, FeP@rGO nanocomposite prepared with the mass ratio of 1:5 (graphene oxide to FeCl3·6H2O) shows the best lithium storage properties. It delivers a reversible discharge capacity of 1000 mA h g−1 at 100 mA g−1 after 100 cycles, as well as an ultra-stable capacity of 460 mAh g−1 at 1000 mA g−1 for 400 cycles. The outstanding lithium storage performance of FeP@rGO nanocomposites opens venues for the potential applications of advanced LIBs.

Graphene oxide (GO) and reduced GO films with different amounts of silver nanoparticles (Ag NPs) have been deposited on quartz and silicon substrates by matrix assisted pulsed laser evaporation (MAPLE). The morphology, structure, chemical composition, and optical and electrochemical properties were evaluated by scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectrophotometry, and cyclic voltammetry measurements. The properties of the films obtained with two types of GO precursors have been compared. A reduction of the amount of oxygen containing groups is observed with the increase of the Ag concentration, which leads to a decrease of the optical band gap. Moreover, the deposition in nitrogen gas ambience leads to the N-doping of rGO material. The films obtained with the highest amount of Ag and with nitrogen doping show potential to be used in energy storage electrodes., The authors thank the financial support of the Executive Unit for Financing Higher Education, Research, Development and Innovation of the Romanian Ministry of Education and Scientific Research under the contract PN-III-P2-2.1-PED-2016-1043, in addition to the Spanish Ministry of Economy, Industry and Competitiveness under the projects ENE2014-56109-C3-1-R and ENE2014-56109-C3-3-R. ICMAB acknowledges financial support from the Spanish Ministry of Economy and Competitiveness, through the “Severo Ochoa” Programme for Centres of Excellence in R&D (SEV- 2015-0496).

Graphene/Si Schottky junction is highly attractive for its application in solar cells due to the excellence of graphene as a transparent conducting electrode. However, the high sheet resistance of the chemical vapor deposition-grown graphene films, mostly used for the solar cells, is still one of the principal factors limiting the power conversion efficiency of graphene/Si solar cells. Here, we report an approach of co-doping with gold (III) chloride (AuCl 3 ) and silver nanowires (Ag NWs) to reduce the sheet resistance (R s ) of graphene as well as to control its work function (W G ) for well-matched graphene/Si wafer junction. The molar concentration (n D ) of AuCl 3 is varied from 1 to 10 mM while the fraction (n A ) of Ag NWs is fixed at 0.1 wt% for the fabrication of the solar cells, based on n A -dependent behaviors of R s and W G . The co-doped graphene/n-Si Schottky solar cells show a maximum power-conversion efficiency of 7.01% at n D = 7.5 mM, resulting from the increased barrier height at the graphene/Si junction and the reduced sheet resistance/transmittance of graphene by the co-doping, as proved from the n D -dependent behaviors of open-circuit voltage, DC conductivity/optical conductivity ratio, series resistance, and external quantum efficiency.

The freestanding flexible graphene oxide electrode material with higher energy density was prepared by the self-assembly process. The graphene oxide film was reduced under the nitrogen atmosphere to form nitrogen doped reduced graphene oxide film (N-rGO). N-rGO films were directly employed as electrodes (both cathode and anode) and solid-state polyvinyl alcohol/phosphoric acid as the separator for the solid-state supercapacitor structure. The structure was characterized without any metallic current collector. The specific capacitance of the device was 397 F/g, higher than that of the conventional liquid electrolyte system used for supercapacitors. The higher capacitance of the N-rGO system significantly increases the energy and power density values. The assembled flexible freestanding solid-state supercapacitor can be potentially used for energy storage applications.

As a novel anode material for lithium-ion batteries, graphene has a higher theoretical capacity than graphite. However, the practical application of graphene suffers from a low coulombic efficiency and poor cycle stability due to the unstable solid electrolyte interphase layer. In this work, ultrathin amorphous TiO2 nanofilm-coated graphene is fabricated by controlled hydrolysis of tetrabutyl titanate on the surface of graphene, and shows superior cycle and rate performance compared to uncoated graphene because amorphous TiO2 nanofilms can prevent the detachment of graphene nanosheets and avoids the formation of thick and unstable solid-electrolyte interphase layers during cycling. Moreover, the electrochemical performance of TiO2-coated graphene can be further improved by controllable calcination of TiO2-coated graphene under a N2 atmosphere. The produced porosity of TiO2 nanofilms after calcination can improve both Li+ and electron transport, leading to the further improved lithium storage performance of graphene. This novel synthesis strategy may be employed in other graphene-based anode materials for high-performance lithium-ion batteries and other electrochemical devices.

Lithium titanium oxide (Li 4 Ti 5 O 12 ) particles were surface-decorated with 1–5% wt. of graphene oxide (GO) using new low temperature method (LTM). All the synthesized materials have been characterized by a number of methods: X-ray powder diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM). The study includes the influence of the graphene oxide flakes decoration on lithium titanium oxide crystal structure. Raman analysis demonstrates a typical spinel spectra of Li 4 Ti 5 O 12 (LTO) and relatively sharp D and G lines of GO structure. The XPS measurements shows the most intense peaks at the binding energy of 284.5 eV, which corresponds to C C/C C in aromatic rings of GO located on the surface of Li 4 Ti 5 O 12 . The peaks observed at 285.8, 286.9 and 288.3 eV belong to C O in hydroxyl and epoxy groups, carbonyl functional groups, and O C O in carboxyl groups, respectively. The correlation between the structural and morphological analysis of spinel Li 4 Ti 5 O 12 structure decorated with graphene oxide (GO) flakes was examined for the first time in this work.

In this study, we report a green and eco-friendly method for direct synthesis of graphene sheet from natural graphite under simple conditions and in situ anchored with MnO 2 via an environmental route. A wet mechanochemical approach is used to exfoliate the graphite to graphene sheet by using citric acid as a non-toxic and friendly intercalator agent instead of strongly corrosive acids such as sulfuric and nitric acids at the shortest time and environmental condition. We carried out various microscopic and spectroscopic measurements such as UV–visible spectroscopy, Fourier transform Infrared (FT-IR), Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) Atomic Force Microscopy (AFM) and Handle Raman Microscopy to confirm the exfoliation of natural graphite to graphene under mild condition. Moreover, we took nanoindentation test for investigation of mechanical properties of graphene sheets. The hardness and elastic modulus obtained from this analysis are about 4.1 and 37.2 GPa, receptivity. At the following work, one pot preparation of graphene-MnO 2 nanocomposite can be performed on the large scale and be utilized in a wide variety of applications. This synthesis, which is economically suitable, is performed without any reduction agent and much purification. Facile synthesis of graphene and graphene-MnO 2 nanocomposite via a green and simple way makes it scalable to apply in many fields.

Reduced graphene oxide coated porous SnO 2 nanotubes are designed as anode for sodium ion batteries (SIBs). The nanocomposites deliver good cycling stability with the capacity retention of 91% extending to 100 cycles at a current density of 50 mA g −1 in the voltage range of 0.01–3.0 V. Moreover, they reveal good rate capability with the reversible capacities of 242.6, 207.7, 173.4, and 140.3 mAh g −1 at various current densities of 50, 100, 200, and 400 mA g −1 , respectively. These results indicate that the coating of reduced graphene oxide is an effective strategy to buffer volume change and improve charge transfer resistance during Na + ion insertion/extraction for SIBs.

Construction of metal oxide/sulfide and carbon-based material nanocomposites is an effective strategy to obtain high-performance electrode materials for supercapacitors. In the present work, graphene oxide nanofibers (GONFs) are selected as the support materials, and the nanocomposite of reduced graphene oxide nanofiber and cobalt sulfide (rGONF/CoS2) is synthesized via a simple and facile method. As an electrode material for pseudocapacitors, the rGONF/CoS2 nanocomposite exhibits a high specific capacitance of 635.8 F g-1 at a current density of 1 A g-1 measured in 6 M KOH electrolyte, which is much higher than that of bare cobalt sulfide. Furthermore, the rGONF/CoS2 nanocomposite has also shown excellent cycling performance with 95.4% capacitance retention over 2000 cycles. In addition, the assembled asymmetric supercapacitor (ASC) device using rGONF/CoS2 nanocomposite as cathode material and activated carbon (AC) as anode material can work at a high operating voltage of 1.65 V and show a maximum energy density of 13.8 W h kg−1 at a power density of 824.6 W kg−1.

Nitrogen doping is considered to be a promising way to improve the performance of graphene-based supercapacitors. It is crucial to discuss that the role of nitrogen doping in regulating the electronic properties. Herein, we chose urea, NH3·H2O and N2H4·H2O as the nitrogen sources to modify the graphene based cobalt oxide composites to compare which nitrogen source made a great improvement on the supercapacitive performance of the composites. When the urea is used as the nitrogen source, the electrochemical performance was the best among the nitrogen-doped (N-doped) graphene based cobalt oxide composites (334.8 F g−1 at a current density of 5 A g−1 in 2 M KOH aqueous solution). Nitrogen doping worked as a modification to control the structure of graphene sheet and effectively improved the electrochemical performances.

LiNi0.5Co0.2Mn0.3O2 powders synthesised via a citric acid assisted sol-gel method were subsequently surface-modified with graphene oxide using a wet chemical method. X-ray diffraction (XRD) results showed that the graphene-oxide-coated LiNi0.5Co0.2Mn0.3O2 powders exhibited only minor differences in their phase-structural composition compared to the original LiNi0.5Co0.2Mn0.3O2 powders. The graphene-oxide-coated LiNi0.5Co0.2Mn0.3O2 sample presented a core-shell structure, with a uniform coating layer with a thickness of about 1 nm discovered on the surface, as confirmed by field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) revealed that the transition metals (M = Ni, Co, Mn) maintained a high oxidation state after surface modification with graphene oxide. The cycle performance of the graphene-oxide-coated LiNi0.5Co0.2Mn0.3O2 was significantly enhanced at a high temperature of 55 °C, leading to a capacity retention of 72% after 100 cycles compared with only 64% for the bare LiNi0.5Co0.2Mn0.3O2. The graphene-oxide-coated LiNi0.5Co0.2Mn0.3O2 also demonstrated better performance at different rates than the pristine sample. The effect of the graphene oxide coating layer was further investigated via electrochemical impedance spectroscopy (EIS), which indicated that this layer plays an important role in stabilising the interface between electrolyte and cathode during cycling.

A uniform composite with NiCo2S4 nanoparticles anchored on graphene sheets is fabricated through an innovative one-step hydrothermal method. The XRD, Raman, XPS, SEM, HRTEM and EDS analyses are performed for characterizing the morphology and microstructure of the as-prepared NiCo2S4/graphene composite. It can be found that NiCo2S4 nanoparticles with a length of 20–50 nm were densely grown on the highly conductive graphene sheets, forming a 3D conductive network for rapid and efficient charge transport. The electrochemical performance is evaluated by CV, GCD and EIS, demonstrating that the NiCo2S4/graphene composite exhibits a very high specific capacitance (1040.6 F g−1) and greatly improved cycling stability (89.3% capacitance retention after 2000 cycles), which are due to the synergistic effect of graphene and NiCo2S4 nanoparticles. An asymmetric device has been assembled with NiCo2S4/graphene as positive electrode and graphene as negative electrode in PVA-KOH gel electrolyte solution. The as-prepared device demonstrates a energy density of 2.9 W h kg−1 with a power density of 872 W kg−1, indicating that the NiCo2S4/graphene composite can serve as a promising electrode material for asymmetric capacitor.

Many metal oxides (e.g., SnO 2 ) are deemed as promising anode materials for lithium-ion batteries due to their high theoretical capacities. However, the low electronic conductivity and large volume change of SnO 2 during cycling hinder its practical application. In this work, graphene-based Pt/SnO 2 composite is prepared by a modified electroless plating method and exhibits superior electrochemical performance compared to graphene-based SnO 2 and Pt/SnO 2 composites. The reversible capacity of graphene-based Pt/SnO 2 is maintained at ∼950 mA h g −1 at 0.1 C after 100 cycles and remains at ∼470 mA h g −1 when the current density increases to 2 C. The graphene substrate can enhance the electronic conductivity of the composite and effectively buffer the strain from the volume variation of SnO 2 during cycling. Moreover, the presence of Pt nanoparticles can separate SnO 2 nanoparticles on the graphene and further facilitate electron transport in the composite, leading to the outstanding electrochemical performance of graphene-based Pt/SnO 2 . This kind of novel graphene-based metal/metal oxide composites may be potentially used as high-performance electrode materials for batteries and supercapacitors.

In this work, a new route for preparation of graphene reinforced aluminum (Al) matrix composites with enhanced dispersion and strength has been discussed based on aqueous suspension mixing procedure. Mg2+ ions added into mixture were used as binding bridge that anchored graphene sheets to the surface of Al powder, improving affinity and binding capacity of graphene sheets with Al matrix. Graphene nanosheets have double dispersion behaviors on Al matrix with increasing of Mg2+ concentration following colloidal theory (DLVO theory and Schulze-Hardy rule). Although composite billet consolidated through spark plasma sintering (SPS) has only 3 wt% content of graphene, but it was significantly reinforced in strength affected by the dispersion degree of graphene on composite matrix.

A novel perovskite CoTiO 3 /graphene composite with a particle size of 100 nm was synthesized by ball-milling and high temperature solid method and utilized as anode materials for lithium-ion batteries. The structure morphology and electrochemical performance of CoTiO 3 /graphene nanocomposite were investigated by X-ray diffraction (XRD), Raman spectroscopy measurements, scanning electron microscopy (SEM), galvanostatic charge-discharge tests and electrochemical impedance spectroscopy (EIS) tests. The CoTiO 3 /graphene nanocomposite delivers a higher stable discharge capacity (∼500 mAh g −1 ) and better cycling stability (86.2%), as well as improved rate capability over 80 cycles, compared with those of bare CoTiO 3 . Moreover, this CoTiO 3 /graphene nanocomposite exhibits stable discharge capacity (∼350 mAh g −1 ) after 3000 cycles at high current density (1 A g −1 ). The improved electrochemical properties of CoTiO 3 /graphene can be attributed to the good conductivity and large surface of graphene and the combination novel nanostructure of CoTiO 3 and graphene.

Despite its high theoretical capacity of 936 mAhg−1, when applied as anodes in lithium-ion batteries, manganese oxide, hausmannite(Mn3O4) face many practical difficulties due to its poor intrinsic electrical conductivity, huge volume expansion, and pulverization during repetitive charge/discharge cycling processes etc. In this manuscript, we report a simple, fast and facile microwave technique for synthesis of Mn3O4 embedded in three dimensional nitrogen doped graphene-carbon nanotube network. Our newly developed technique not only effectively reduces graphene oxide but also results in growth of nitrogen doped carbon nanotubes on graphene substrate to give unique mesoporous, 3-D hierarchical carbon nano-architectures. When applied as negative electrode in lithium-ion batteries, our 3D graphene-carbon nanotube hybrids exhibit high capacity of 1337 mAhg−1 even after 300 cycles.

In this study, reduced graphene oxide-TiO 2 (rGO-T) composite films fabricated by a spray coating method are proposed to develop a multifunctional material with transparent conductive, photocatalytic and strain sensing properties. In the presence of SDBS, well-dispersed reduced graphene oxide solutions were prepared by mixing graphene oxide dispersions with hydrazine hydrate. A drastic synergetic effect was found simply by mixing reduced graphene oxide dispersions with TiO 2 solutions. The obtained multifunctional rGO-T composite films showed relatively high optical transmittance, excellent strain sensing property with tunable gauge factors (GF) of 11–21 and enhanced photocatalytic property. The remarkable performance could be attributed to the combination of the excellent electrical and mechanical properties of graphene nanosheets and photocatalytic performance derived from TiO 2 nanoparticles. Overall, this work could provide new insights into the research of the graphene-TiO 2 composite materials and facilitate their application in a broad range.

Enhanced composites of V2O5/Graphene with delicate structure were successfully designed and synthesized via a smart route. SEM, TEM, XRD, Raman spectra and XPS survey revealed the morphology and structure of V2O5/Graphene composites. The BET surface area and total BJH pore volume of V2O5/Graphene composites were much higher than these of bare V2O5 nanowires. Compared with bare V2O5 nanowires, the V2O5/Graphene composites exhibited improved electrochemical performance. It revealed a discharge capacity of 190.9 mA g−1 in the third cycle and capacity retention of 96.6% after 150 cycles, whereas the bare V2O5 nanowires were 141.8 mA g−1 and 76.5%, respectively. It was noteworthy that the strategy of position-fixing V2O5 nanowires on graphene sheets played a crucial role in the formation of the stable structure of composites. The achieved V2O5/Graphene composites effectively increased the electrical conductivity and electroactive sites, buffered the volume change and provided large contact area during the charge/discharge process. The proposed approach here to obtain composite in this work would render an effective way to improve the electrochemical performance of metal oxide for LIBs.

Graphene is considered as an excellent reinforcement in composite materials because of its unique physical and mechanical properties. In this study, graphene was successfully prepared at the reducing temperature of ambient temperature by oxidation reduction process using a green reducing agent and an attempt was made to fabricate graphene/W70Cu30 composites by mechanical alloy and pressureless infiltration sintering technology. Effect of graphene addition on W70Cu30 powders and W70Cu30 composites were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, Optical microscopy (OM) and HB-3000 hardness tester. The results show that the graphene could remain after ball milling and sintering process. But, the carbides (like WC and W 2 C) were also formed in bulk composites, which revealed that some of graphene would react with W during the sintering process, but the graphene coated with Cu phase in W70Cu30 alloy still keep intrinsic structures. And W grain size is efficiently refined with addition of graphene. The relative density of graphene/W70Cu30 composites enhance with the content of graphene increasing. When the graphene content is 1.0 wt%, the relative density of composites reach up to 98.4%, which is considered that graphene could improve the wettability of W and Cu. The incorporation of graphene into W7Cu30 alloy gradually increases the hardness of composites, which is enhanced about 21% compared with the pure W70Cu30 when the graphene content is 1.0 wt%. The electrical conductivity of composites increase gradually firstly and decrease sharply with the increase of graphene content. When the 0.5 wt% graphene was added to the W70Cu30 alloys, the maximum conductivity reaches ∼46% IACS.

Transition metal oxides are attractive as anode materials in lithium-ion batteries for their high theoretical capacity and good performance. In this work, an anode material based on manganese-based oxide FeMnO3 in LIBs is investigated for the first time. FeMnO3 is prepared with graphene and the FeMnO3/graphene composite exhibits a high discharge capacity of 1155.3 mAh g−1 after 300 cycles at 200 mA g−1, as well as a superior rate performance of 851.7 mAh g−1 at a current density of 3200 mA g−1. The observed extraordinary performance is believed to be attributed to the combination of the intrinsically high capacity of FeMnO3, a large surface area of 89.65 m2 g−1 and good electrical conductivity of the FeMnO3/graphene composite. To help clarify the properties of this new material, we employ first principles calculations to determine the structural stability, electronic structure, and Li ion diffusivity of FeMnO3. The calculations show that FeMnO3 has a relatively low band gap (an indication of reasonable electrical conductivity) and Li ions exhibit a large room temperature diffusivity in FeMnO3.

As an n-type inorganic semiconductor, ZnO has been widely used in hybrid solar cells (HSCs) due to its numerous characteristics such as low cost, easy synthesis, non-toxicity and good optoelectronic properties. In this work we have synthesized the ZnO nanostructures/nanoparticles via wet chemical route having Zinc Acetate Dihydrate (ZnADH) as precursor, Poly (Ethylene Glycol) block poly (Propylene Glycol) block poly (Ethylene Glycol) (PEG-PEG-PEG/P123) as template directing agent. Graphene oxide (GO) was prepared by the Modified Hummer's Method through the oxidation of graphite flakes and KMnO 4 was used as an oxidizing agent. ZnO/Graphene nanocomposites were prepared via sonication process. Oxidation peaks of graphite showed by the UV–Vis spectroscopy were around 216 nm and all composite films were observed to be appeared in visible region. A considerable reduction in bandgap of ZnO from 3.1eV to 2.9eV was observed due to incorporation of graphene oxide which was confirmed with both UV–Vis bandgap analysis method and cyclic voltammetry (CV). Measureable progress in the performance of IV characteristics of hybrid solar cells was achieved using the ZnO/Graphene composite as electron collector in active layer along with P3HT:PCBM in an inverted hybrid photovoltaic device. Short circuit current was observed to be improved by approximately four times then its original value in these devices along with the increase in the concentration of GO whereas open circuit voltage showed a decreasing trend.

A simple hydrothermal process for fabrication of a nanocomposite comprising Fe 2 O 3 anchored on three-dimensional (3D) reduced graphene oxide aerogel (rGOA) was developed by using Fe(NO 3 ) 3 and graphene oxide (GO) as precursors and urea as precipitation agent. The morphology and structure of the Fe 2 O 3 /reduced graphene oxide aerogel (Fe 2 O 3 /rGOA) composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) and Raman spectroscopy. An interconnected 3D network structure, which can allow rapid electrolyte ions diffusion and fast electron transport, was formed by the self-assembly of graphene oxide sheets decorated with Fe 2 O 3 nanoparticles. The particle sizes of Fe 2 O 3 ranged from 30 to 50 nm and were hardly affected by the amount of Fe 2 O 3 loaded into rGOA. The electrochemical properties of the Fe 2 O 3 /rGOA composites were studied using cyclic voltammetry and galvanostatic charge/discharge measurement by a three-electrode system. The as-prepared Fe 2 O 3 /rGOA composites exhibited a specific capacitance as high as 522 F g −1 at 20 A g −1 within the operated voltage window (−1.1 to 0.3 V). The excellent electrochemical performance of Fe 2 O 3 /rGOA was interpreted to be due to the synergistic effect of Fe 2 O 3 particles and rGOA.

It’s significant to find an atom-economic way to prepare graphene-manganese oxide nanocomposites for supercapacitors. Herein, a highly atom-efficient strategy is reported to synthesize reduced graphene oxide (rGO)-Mn 3 O 4 nanoparticles composite for supercapacitors. First, rGO/MnSO 4 suspension is obtained by hydrothermal reduction of graphene oxide (GO)/MnSO 4 suspension, which is directly produced via Hummers method, and then rGO-Mn 3 O 4 nanoparticles composites are prepared by precipitation of Mn 3 O 4 nanoparticles anchored in-situ on rGO sheets. The as-prepared rGO-Mn 3 O 4 nanocomposites with 86.96% Mn 3 O 4 exhibit high specific capacitance of 258.6 F g −1 and 186.2 F g −1 at 0.25 A g −1 , when using 2 M KOH and 1 M Na 2 SO 4 solution as electrolyte, respectively. More importantly, with the wastewater recovered in the preparation process as electrolyte, the rGO-Mn 3 O 4 composites can deliver a high specific capacitance of 221.6 F g −1 at 50 mA g −1 and 97.1% of the initial capacitance is retained after 1000 cycles at 1 A g −1 . In addition, the rGO-MnO 2 nanosheets composites can also be obtained via a similar strategy. Obviously, this work provides an atom-efficient way for preparation of rGO-manganese oxide nanocomposites for supercapacitors by fully utilizing effective components of the reaction system, including the wastewater.

International audience; The crystal growth of Bismuth-based compounds (mainly Bi2O2CO3) on graphene with various degrees of oxidation in hydrothermal process is reported. The graphene sheets with different concentrations of oxygen-containing groups and defects, as a special carbon source, can effectively influence the phase compositions, morphologies and even photoelectric properties of graphene-Bi2O2CO3 composites through the binding behavior of graphene oxide in the nucleation and growth process of Bi2O2CO3 crystals. The cube-like crystals including mainly Bi2O2CO3 phase with Bi2O3 tightly wrapped by numerous graphene sheets are synthesized employing highly oxidized graphene oxide (HGO) as starting materials, while the partially oxidized graphene oxide (PGO) is used for synthesizing 3D flower-like hierarchical Bi2O2CO3 microstructures just containing Bi2O2CO3 phase adorned with sporadic graphene sheets. Furthermore, the higher charge separation yield is achieved for cubic composites with much more interfacial connection between the cube-like crystals and graphene sheets compared to flower-like crystals. The above results suggest an interesting approach for controlling the morphology and property of crystals by tuning the functional groups on graphene sheets used in the nucleation and growth process of crystals. (C) 2016 Published by Elsevier B.V.

The wide application of reduced graphene oxide (rGO) in water treatment is mainly suffered from high cost and difficult reusage. To addressing these issues, a series of zinc ferrite-reduced graphene oxide (ZF-rGO) nanocomposites with enhanced magnetic properties were successfully prepared using graphene oxide (GO), Fe3+, Zn2+ and ethylene glycol (EG) via a one-pot solvothermal method and the adsorption property was evaluated by the adsorption amount of methylene blue (MB) solution on the samples. The results indicate the as-prepared materials possess good adsorption and cycling properties for MB molecules. The dominated reason is mainly ascribed to the π-π stacking between dye molecules and rGO. Simultaneously, the adsorption kinetic behavior of MB molecules is also discussed and follows pseudo-second-order kinetic very well. Particularly, the introduction of Fe2+ enhances the magnetic property of ZF component in ZF-rGO composite by the reducing action of EG, which ensures the outstanding magnetic separability of the ZF-rGO materials as the adsorbent. Thus, the as-prepared nanocomposite material can be a potential excellent absorbent for removing dye pollutants.