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Development of multifunctional electrocatalysts with high efficiency and stability is of great interest in recent energy conversion technologies. Herein, a novel heteroelectrocatalyst of molecular iron complex (FeMC)‐carbide MXene (Mo2TiC2Tx) uniformly embedded in a 3D graphene‐based hierarchical network (GrH) is rationally designed. The coexistence of FeMC and MXene with their unique interactions triggers optimum electronic properties, rich multiple active sites, and favorite free adsorption energy for excellent trifunctional catalytic activities. Meanwhile, the highly porous GrH effectively promotes a multichannel architecture for charge transfer and gas/ion diffusion to improve stability. Therefore, the FeMC–MXene/GrH results in superb performances towards oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in alkaline medium. The practical tests indicate that Zn/Al–air batteries derived from FeMC–MXene/GrH cathodic electrodes produce high power densities of 165.6 and 172.7 mW cm−2, respectively. Impressively, the liquid‐state Zn–air battery delivers excellent cycling stability of over 1100 h. In addition, the alkaline water electrolyzer induces a low cell voltage of 1.55 V at 10 mA cm−2 and 1.86 V at 0.4 A cm−2 in 30 wt.% KOH at 80 °C, surpassing recent reports. The achievements suggest an exciting multifunctional electrocatalyst for electrochemical energy applications. [ABSTRACT FROM AUTHOR]

A novel hybrid of small core@shell structured CoSx@Cu2MoS4 uniformly hybridizing with a molybdenum dichalcogenide/N,S‐codoped graphene hetero‐network (CoSx@Cu2MoS4‐MoS2/NSG) is prepared by a facile route. It shows excellent performance toward the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) in alkaline medium. The hybrid exhibits rapid kinetics for ORR with high electron transfer number of ≈3.97 and exciting durability superior to commercial Pt/C. It also demonstrates great potential with remarkable stability for HER and OER, requiring low overpotential of 118.1 and 351.4 mV, respectively, to reach a current density of 10 mA cm−2. An electrolyzer based on CoSx@Cu2MoS4‐MoS2/NSG produces low cell voltage of 1.60 V and long‐term stability, surpassing a device of Pt/C + RuO2/C. In addition, a Zn‐air battery using cathodic CoSx@Cu2MoS4‐MoS2/NSG catalyst delivers a high cell voltage of ≈1.44 V and a power density of 40 mW cm−2 at 58 mA cm−2, better than the state‐of‐the‐art Pt/C catalyst. These achievements are due to the rational combination of highly active core@shell CoSx@Cu2MoS4 with large‐area and high‐porosity MoS2/NSG to produce unique physicochemical properties with multi‐integrated active centers and synergistic effects. The outperformances of such catalyst suggest an advanced candidate for multielectrocatalysis applications in metal‐air batteries and hydrogen production. [ABSTRACT FROM AUTHOR]

The fabrication of an effective electrocatalyst for cathodic oxygen reduction reaction (ORR) is important to enhance the performance of fuel cell applications. Here, we prepared a novel hybrid material based on the combination of iron single atoms–small iron nanoparticles homogeneously distributed on the surface of nitrogen-doped graphene nanosheets (Fe SA -Fe NPs /NG). The achieved Fe SA –Fe NPs /NG material exhibited high catalytic ORR behaviors with high positive values of +0.94 V and +0.81 V for onset potential and half-wave potential, respectively, as well as the remarkable stability with 90% retention of initial current over an operation period of 15 000 s), superior to commercial Pt/C in 0.1 M KOH medium. In addition, the material favored a four-electron reaction pathway along with good methanol crossover tolerance towards ORR. The outstanding catalytic performance could be attributed to the formation of a unique microporous nanoarchitecture owning large specific surface area of 103.63 m2 g−1 and high conductivity, which create rich active sites and fast charge transfer ability, thus effectively accelerating the adsorption and catalyzation processes to convert oxygen reactant to product during ORR. These findings suggest a novel route for the synthesis of potential catalysts exhibiting excellent efficiency and cost effectiveness for fuel cell industries. [Display omitted] • The functional catalyst of Fe SA –Fe NPs /NG is rationally prepared via simple route. • The formation of Fe SA –Fe NPs /NG produces more active sites and high conductivity. • The catalyst requires a positive onset potential of +0.94 V for ORR in 0.1 M KOH. • The catalyst shows good stability superior to commercial Pt/C in alkaline media. [ABSTRACT FROM AUTHOR]

The present work highlights the effective H-π interaction between metallocenes (ferrocene; Fc) and graphene and their stabilization in the presence of polyaniline (PANI) through π-π interactions. The PANI-stabilized Fc@graphene nanocomposite (FcGA) resembled an intertwined network-like morphology with high surface area and porosity, which could make it a potential candidate for energy-storage applications. The relative interactions between the components were assessed through theoretical (DFT) calculations. The specific capacitance calculated from galvanostatic charging/discharging indicated that the PANI-stabilized ternary nanocomposite exhibited a maximum specific capacitance of 960 F g− at an energy density of 85 Wh Kg−1 and a current density of 1 A g−. Furthermore, electrochemical impedance spectroscopy (EIS) analysis confirmed the low internal resistance of the as-prepared nanocomposites, which showed improved charge-transfer properties of graphene after incorporation of Fc and stabilization with PANI. Additionally, all electrodes were found to be stable up to 5000 cycles with a specific capacitance retention of 86 %, thus demonstrating the good reversibility and durability of the electrode material. [ABSTRACT FROM AUTHOR]

A newly designed counter electrode (CE) composed of a hybridized structure of iron nitride (FeN) core-shell nanoparticles grown on nitrogen-doped graphene (NG) is presented for application in dye-sensitized solar cells (DSSCs). The FeN core-shell nanoparticles on NG show an excellent electrocatalytic activity and lower charge-transfer resistance ( Rct) towards the CE (I−/I3−) redox reaction in DSSCs. The hybridized electrode exhibits remarkable cycling stability even after 500 cycles. The energy conversion efficiency of a DSSC cell with core-shell FeN/NG nanohybrids as the CE reaches 10.86%, which is superior to the energy conversion efficiency of 9.93% for a cell with a conventional Pt CE under the same experimental conditions. This work provides a novel approach to fabricate catalytically active electrodes for DSSCs and promotes the development of metal nitride-based electrodes for photovoltaic applications. [ABSTRACT FROM AUTHOR]

• Non-precious novel bimetallic oxide of Fe 2 O 3 -MoO 3 /NG core-shell catalyst prepared first-time. • Uniformly nano-sized core Fe 2 O 3 -MoO 3 NPs homogeneously dispersed and wrapped by shell NG sheet. • Incorporation of MoO 3 with Fe 2 O 3 could modify the electronic structure of entire bimetallic oxide. • Synergistic surface-strain capabilities are engineered by segregation of atomic arrangements. • Fe 2 O 3 -MoO 3 /NG deliver superior catalytic activity along with remarkable durability/ stability. In-expensive transition metal catalysts are the most favorable substitutes to the noble metal catalysts for oxygen reduction reaction (ORR) in fuel cells energy technology. Herein, the article focused on the synthesis of uniformly distributed nano-sized bimetallic Fe 2 O 3 -MoO 3 oxide encapsulated nitrogen-doped graphene (NG) (Fe 2 O 3 -MoO 3 /NG core-shell structure) catalyst through well-controlling reaction parameters and its prospective applications towards ORR for the first time. Thus, these unique synergistic interactions of bimetallic Fe 2 O 3 -MoO 3 and NG support could modify the surface-strain effects, which led to enriching catalytic activity. Thus, Fe 2 O 3 -MoO 3 /NG core-shell structure demonstrated excellent catalytic activity, and far exceeding in long-term durability, better methanol tolerance compared to commercial Pt/C catalyst. Furthermore, the monometallic oxide (Fe 2 O 3 or MoO 3) or NG individually have poor activity for ORR, but their hybrid materials (Fe 2 O 3 -MoO 3 /NG) influenced strongly due to their structural properties, such as crystal structure, exclusive porosity, particle size and multiple active interfaces, display unexpected and remarkably high ORR activities similar to Pt/C in alkaline medium, This makes Fe 2 O 3 -MoO 3 /NG core-shell structure a suitable and efficient non-precious electrocatalysts with high catalytic ability, that could open up a new promising approach to advanced catalysts for electrochemical energy conversion and storage. [ABSTRACT FROM AUTHOR]

To meet a fast‐emerging demand, flexible energy storage applications have a great interest in the development of highly flexible hierarchical nanoarchitectures. Metal nitrides have recently been paid a significant interest as a promising electrode material for supercapacitors (SCs) owing to their high electrical conductivity, excellent redox properties, and outstanding mechanical strength. However, poor electrochemical stability seriously limits the commercialization possibilities. Herein, a novel strategy is presented for the synthesis of nitrogen‐doped graphene encapsulated with ultrasmall nickel–cobalt nitride (NiCo2N) and nickel–iron nitride (NiFeN) core–shell architectures that are explored as advanced electrodes for flexible solid‐state SC. The flexible NiCo2N@NG//NiFeN@NG asymmetric SC delivers an ultrahigh energy density of ≈94.93 Wh kg−1 at 0.79 kW kg−1, exceptional power density (≈74.67 Wh kg−1 at 39.53 kW kg−1), and ultralong cycle life (≈5.07% drop in initial capacity after 25 000 cycles). These results promote the core–shell hybrids that can be served as advanced supercapacitor materials for flexible energy storage applications. A novel strategy for the synthesis of nitrogen‐doped graphene encapsulated nickel–cobalt nitride (NiCo2N) and nickel–iron nitride (NiFeN) core–shell architectures is demonstrated herein. The composites are explored as advanced electrodes for flexible asymmetric supercapacitors (ASCs). The flexible ASC delivers an ultrahigh energy density of ≈94.93 Wh kg−1 at 0.79 kW kg−1 and ultralong cycle life. [ABSTRACT FROM AUTHOR]

A series of proton-functionalized graphitic carbon nitride ( f gC 3 N 4 ) modified reduced graphene oxide (rGO)/nickel-aluminium layered double hydroxide (LDH) composites ( f gC 3 N 4 -rGO/LDH-1 and f gC 3 N 4 -rGO/LDH-2) were prepared by a novel scalable strategy using different amounts of f gC 3 N 4 -rGO as a conductive matrix. The morphological analyses reveal that the LDH sheets are gradually assembled on the f gC 3 N 4 -rGO matrix. The f gC 3 N 4 -rGO and LDH mutually minimize their self-aggregation in f gC 3 N 4 -rGO/LDH composite. The porous skeleton of f gC 3 N 4 -rGO/LDH-1 (highest loading of f gC 3 N 4 -rGO matrix) produces a high surface area (240 m 2 /g) and mesopores (diameter; 2.2 nm). The f gC 3 N 4 -rGO/LDH-1 electrode generates a specific capacitance value of 1190 F g −1 at 1 A g −1 , excellent rate performance (71% at 10 A g −1 ), and good cycling stability (90% after 3000 cycles), in a three-electrode setup. Hierarchical f gC 3 N 4 functionalized rGO composite (3D- f gC 3 N 4 @rGO) was used as a negative material. The 3D- f gC 3 N 4 @rGO produces an excellent capacitance of 345 F g −1 at 1 A g −1 , high rate capability (74% at 10 A g −1 ) and good cyclic stability (90% after 3000 cycles). The f gC 3 N 4 -rGO/LDH-1 and 3D- f gC 3 N 4 @rGO were assembled to fabricate a solid-state asymmetric supercapacitor device using KOH/PVA gel electrolyte. The device operates within the potential window of 1.6 V and produces the highest energy density and power density of 54.76 W h kg −1 and 12031.92 W kg −1 , respectively. The solid-state device shows an excellent cycle life of 91% after 7000 cycles, and it can power a red LED, suggesting very efficient for practical application. [ABSTRACT FROM AUTHOR]

In this study, a novel 4,4′-diaminostilbene-2,2′-disulfonic acid (DASDSA)-functionalized reduced graphene oxide (DASDSA-rGO) was prepared via simple refluxing method involving GO and DASDSA in the presence of ammonia solution followed by reduction with hydrazine hydrate. FTIR spectroscopy, Raman scattering, X-ray photoelectron spectroscopy (XPS), and XRD analyses confirmed the successful functionalization and reduction of GO in DASDSA-rGO. The FTIR and XPS analyses also confirmed covalent bond formation between DASDSA and graphene. The DASDSA spacer successfully minimized the restacking of rGO sheets as observed from FESEM analysis. Several redox transition states and SO 3 H groups of grafted DASDSA moieties provided excellent pseudocapacitance performance of the DASDSA-rGO electrode. The DASDSA-rGO electrode showed high specific capacitance ( C ) value of 1042 F g −1 at a current density of 1 A g −1 , good cycling stability (95% capacitance retention after 3000 cycles), and excellent rate capability in a three-electrode setup. The DASDSA-rGO (positive electrode) and rGO (negative electrode) were assembled to prepare an asymmetric supercapacitor (ASC) device. The power density values of the ASC device were calculated to be 650 and 7800 W kg −1 at energy density values of 37.37 and 23.78 W h kg −1 , respectively. The ASC device exhibited C value of 159 F g −1 at 1 A g −1 and displayed 86% retention in C after 8500 cycles. The EIS data of the three-electrode system and ASC device were fitted with Z-views to determine the different resistance components after a different number of charge–discharge cycles in a cycling stability test. [ABSTRACT FROM AUTHOR]

The catalytic activity and durability are important factors to the commercial deployment of proton exchange membrane fuel cells (PEMFCs). Recent observations offer that carbon-based support materials can significantly improve the catalytic activity, durability and long-term stability. Here, we report a new strategy for the fabrication of Pt nanoparticles (NPs) supported 3D graphene nanosheets (Pt/3D-GNS) hybrid architecture using polyvinylpyrrolidone-Nafion complex (PNC) to boost the catalytic properties in PEMFCs. The 3D hybrids nanostructure are characterized by FE-SEM, TEM, XRD, Raman and XPS analysis. FE-SEM and TEM analysis reveal that the as-synthesized Pt/3D-GNS were of high quality and well-ordered ∼5–7 nm Pt NPs particles uniformly dispersed on 3D graphene nanosheets. Impressively, Pt/3D-GNS exhibited excellent catalytic activity, outstanding durability and long-term stability than that of commercial electrode material (Pt/C). The improvement in extraordinary electrochemical performance can be endorsed to the unique morphology, high porosity, excellent conductive networks, and intense networking of Pt NPs and 3D graphene sheets in the hybrid matrix. These findings open a new path way to designate the Pt/3D-GNS hybrids as promising low-cost, highly catalytic active, durable and long-cycle life electrode materials for the development of high performance PEMFCs. [ABSTRACT FROM AUTHOR]

A series of novel polyethyleneimine (PEI) modified graphene oxide (PEI-mGO) filled poly(vinyl alcohol) (PVA) nanocomposite (PEI-mGO/PVA) films were prepared by solution-casing for hydrogen gas barrier applications. Hydrophilic PEI was used to simultaneously reduce and modify graphene oxide sheets, thereby facilitating a homogeneous dispersion of PEI-mGO in the PVA matrix. The effects of PEI-mGO on the morphology and properties of the nanocomposite films were examined by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and field emission scanning electron microscopy. Analogous GO/PVA composites were also prepared and characterized for comparative purposes. The PEI-mGO/PVA nanocomposites showed higher thermal and mechanical stability as well as remarkable improvement in hydrogen gas barrier properties compared to the PVA film; specifically, the PEI-mGO/PVA film having 3.0 wt% of PEI-mGO content exhibited almost 95% decrease in GTR and permeability values compared to PVA film. [ABSTRACT FROM AUTHOR]

Highlights: [•] Novel water-dispersible aryl diazonium salt functionalized graphene (ADS-G) prepared using reduced graphene oxide (r-GO). [•] The poly(vinyl alcohol) (PVA)/ADS-G composite was successfully prepared by a simple solution casting. [•] 181% improvement in tensile strength of the PVA/ADS-G has been achieved with 2.0wt.% of ADS-G. [ABSTRACT FROM AUTHOR]

Abstract: The toughening effects of 3-aminopropyltriethoxysilane (APTES) functionalized silica nanoparticles attached graphene oxide (ATGO) in epoxy were investigated. Fourier transform infrared and X-ray photoelectron spectroscopy analysis confirmed chemical functionalization and partial reduction of GO during the functionalization. The nanostructures of GO and ATGO were observed by transmission electron microscopy. The tensile strength and modulus of 1wt.% ATGO-filled epoxy composites at cryogenic temperature (CT) were 29.2% and 22.0% higher than those of pure epoxy. Interestingly, both the tensile strength and modulus of all the composites at CT were significantly higher than those at room temperature (RT). In contrast, impact strength of the composites at RT was higher than that at CT due to the restricted molecular mobility of epoxy. The fracture toughness (K IC) obtained from the single edge notched bending (SENB) test increased sharply with an increase in ATGO loading in the epoxy up to 1wt.%. The fracture surfaces of the composites analyzed through field emission scanning electron microscopy (FE-SEM) shown the rough surfaces confirming the enhanced impact and tensile properties of the ATGO filled composites. [Copyright &y& Elsevier]

Abstract: The efficient synthesis of graphene sheets using pyrrole as a reducing agent was explored. The obtained graphene sheets were dispersible in organic solvents such as ethanol, isopropanol, N,N-dimethylformamide, N-methylpyrrolidone, dimethylsulfoxide, tetrahydrofuran, and acetone. During this reduction reaction, pyrrole was oxidized, forming oxidation product of pyrrole and adsorbed on the graphene sheets surface by π–π interaction. The oxidation product of pyrrole acted as a capping agent for graphene sheets by preventing re-stacking and formed organically dispersible graphene. The formation of graphene and its crystalline nature was indicated by the transmission electron microscopy and the atomic force microscopy analysis. Raman, X-ray photoelectron spectroscopy and X-ray diffraction provided the evidence for graphene formation from graphene oxide precursor. Furthermore, the reduced oxygen content and N 1s peak observed by the X-ray photoelectron spectroscopy analysis of graphene sheets confirmed the reduction reaction and presence of adsorbed oxidation product on the surface of graphene sheets. The resulting graphene sheets were readily dispersible in solvents and easily to process. [Copyright &y& Elsevier]

In this work, cobalt vanadate/reduced graphene oxide (Co 3 V 2 O 8 /RGO) composite nanostructure has been synthesized via in-situ reduction of graphene oxide (GO) in the presence of cobalt chloride and sodium metavanadate through hydrothermal following post calcinations treatment. Characterizations through various techniques have been performed to probe the physicochemical properties of Co 3 V 2 O 8 /RGO, RGO and Co 3 V 2 O 8 nanostructures. Our Results show that because of the synergistic effect, Co 3 V 2 O 8 /RGO composite nanostructure exhibits superior electrochemical properties as compared to bare RGO and Co 3 V 2 O 8. At a current density of 0.5 A/g the specific capacity has been recorded to be 118.82, ∼179, and ∼241.67 Cg-1 in case of Co 3 V 2 O 8 , RGO and Co 3 V 2 O 8 /RGO nanostructures, respectively. Moreover, Co 3 V 2 O 8 /RGO composite nanostructure (positive electrode) and RGO (negative electrode) have been employed to prepare the asymmetric supercapacitor, exhibited high specific capacity (127.62Cg-1), energy density (28.36 Whkg−1), and power density (400 Wkg-1) at a current density 0.5 A/g. This asymmetric supercapacitor shows excellent capacity retention (∼91.64%) and columbic efficiency (∼98.61%) measured at a current density of 5 A/g after 10,000 charge/discharge cycles. More importantly, a dramatic increase ∼170% (344 Cg-1) and ∼67% (185 Cg-1) in the specific capacity have been recorded at a current density of 0.5 A/g and 1.0 A/g, respectively when asymmetric supercapacitor device is subjected to an external magnetic field of strength of 0.5 T. Additionally, under the applied magnetic field, capacity retention ∼97.75% and columbic efficiency ∼98.84% has been recorded at a current density of 5 A/g after 10,000 cycles. [Display omitted] • Synthesis of Co 3 V 2 O 8 /RGO composite nanostructure via a facile in-situ reduction. • Co 3 V 2 O 8 /RGO nanostructure exhibited specific capacity of ~242 Cg-1 at 0.5 Ag-1. • Co 3 V 2 O 8 /RGO exhibits ~103% higher specific capacity compare to bare Co 3 V 2 O 8 NPs. • ASc exhibits energy density ~28.36 Whkg-1 and power density ~ 400 Wkg-1 at 0.5 Ag-1. • Capacity retention ~91.64 % and columbic efficiency ~98.61 % at 5 Ag-1 after 10,000 cycles. • Magnetic field induced ~170% enhanced capacity at 0.5 Ag-1. [ABSTRACT FROM AUTHOR]

Abstract Polyelectrolyte-decorated graphene with positive and negative charges was prepared using graphene oxide as a precursor along with polyallylamine hydrochloride and poly (styrenesulfonate sodium) as surface modifiers, respectively. Driven by an electrostatic interaction, the as-obtained polyelectrolyte-decorated graphene sheets were self-assembled via a layer-by-layer method, producing graphene based composite multilayers. Field emission scanning electron microscopy (FE-SEM) images showed that the surface of composite film exhibited a mass of characteristic wrinkles of graphene. Interestingly, the cross-sectional FE-SEM of the film exhibited an unstratified structure, indicating a good dispersion of graphene sheets in the composite film. The results of oxygen gas permeability testing demonstrated that the resulting composite films exhibited excellent oxygen gas barrier properties. The oxygen gas transmission rate (OTR) of the composite film with 24 bilayers was as low as 1.2 cm3 m-2 d-1∙atm−1, exhibiting potential for use in packaging applications. [ABSTRACT FROM AUTHOR]

Development of highly functional and durable catalysts in a cost-effective way is a promising approach for practical energy conversion applications. In this study, a novel catalyst, cobalt iron carbide nanoparticles encapsulated by nitrogen doped graphene nanosheets, is successfully synthesized through a simple refluxing strategy followed by a post annealing process. It is found that the catalyst exhibits excellent catalytic activity for oxygen reduction reaction in alkaline medium. The oxygen reduction reaction kinetics of the catalyst mainly follow a 4-electron transferred pathway along with good diffusion limit current density, highly positive onset potential (−0.04 V) and half-wave potential (−0.11 V). In addition to catalytic activity, the catalyst demonstrates advanced superior stability, and excellent methanol tolerance in comparison with commercial platinum catalyst. The impressive catalytic performance of the catalyst is attributed to the unique mesoporous metal-core/graphene-shell architecture in which high interactions between two transition metals and transition metal-carbon synergistically provide enhanced catalytically active sites, accelerate interfacial charge transfer, and optimize oxygen adsorption energy. The results demonstrate that such catalyst can be an alternative low-cost and efficient catalyst for oxygen reduction reaction in energy conversion applications. [ABSTRACT FROM AUTHOR]

Recently, the research effort on two-dimensional transition metal dichalcogenides/graphene (2D-TMDs/Gr) hybrids has grown. These hybrids are emerging as a promising strategy for the preparation of advanced multifunctional materials with effectively upgraded properties, as well as performances. Due to their outstanding electrical, physical, and chemical properties, these materials have been extensively considered for various applications, both in academia, and industry. This review systematically assesses the important progress to date in the development of 2D-TMDs/Gr hybrids. The synthesis methods of 2D-TMDs/Gr hybrids for fabricating diverse types of nanostructured architectures are highlighted. In addition, the relationships between morphological and structural characteristics, and the physicochemical properties of 2D-TMDs/Gr hybrids, are recognized in detail. This review also discusses recent prospective applications of the 2D-TMDs/Gr hybrids in the areas of energy storage, energy conversion, energy harvesting technologies, and sensors. In summary, although there are still challenges for optimizing the synthesis process and performance of the 2D-TMDs/Gr hybrids, they offer unique candidates for a wide range of promising applications in the future. [ABSTRACT FROM AUTHOR]

In this study, a novel hierarchical porous network of Pt 51 Pd 49 alloy-integrated graphene nanosheet as active catalyst towards ethanol oxidation was fabricated using electroless deposition followed by chemical vapour deposition for the first time. Such materials were obtained as a three-dimensional continuous and non-order porous architecture with good dispersion and uniformity of the ultrasmall Pt 51 Pd 49 nanoalloy particles (∼3 nm) within the graphene nanosheets. As an electrocatalyst, it exhibited excellent catalytic behaviour towards ethanol oxidation with superior conversion, long-term stability and better tolerance towards intermediate's poisoning effect, as compared to commercial Pt black product. The results were associated with the enhanced electroactive surface area and mass transfer possibility of the catalyst due to the formation of an unique porous nanostructure for Pt 51 Pd 49 alloys. In addition, the coating effect of graphene nanosheets over Pt 51 Pd 49 alloy nanoparticles avoided aggregation and dissolution, possibly allowing full utilization of the active sites from all nanoparticles, and thus efficiently improving charge transfer ability and working stability of the catalyst. Owning high quality, good electrochemical performance, and ease of synthesis, the as-synthesized catalyst opens an interesting nanoarchitecture class for efficiently catalyzing ethanol oxidation in fuel cells. [ABSTRACT FROM AUTHOR]

A high quality graphene-encapsulated AuAg alloy (AuAg-GR) nanohybrid with homogeneous structure and good reproducibility over a desired area was successfully fabricated. Taking benefits of the unique architecture, such nanohybrid was employed as an efficient electrocatalyst for sensing application. The AuAg-GR based sensor could sensitively detected neurotransmitter serotonin (5-HT) with wide linear detection range (2.7 nM to 4.82 μM), very low detection limit (1.6 nM), negligible interference, and excellent reproducibility. In addition, AuAg-GR based sensor accurately determined 5-HT in human serum samples. This is due to the enhanced catalytic activity of GR nanosheets-encapsulated AuAg nanostructures, which possessed well monodispersion of AuAg alloy, greater electrochemical active sites, and good charge transfer possibility. The obtained results imply that such nanohybrid is a potential candidate for synthesizing electrochemical sensors in requirement of high sensitivity, long-term stability, and good reproducibility. [ABSTRACT FROM AUTHOR]

A novel carbon felt/nitrogen-doped reduced graphene oxide/paraffin wax ternary skeleton (CF/N−RGO/PW) is developed to enhance the tribological performances of monomer casting nylon-6 (MCPA6). FE−SEM results confirm the successful formation of the three-dimensional (3D) CF/N−RGO/PW skeleton, where N−RGO sheets are decorated on carbon fibers. Most importantly, the flexuous N−RGO sheets can accommodate PW to provide sufficient lubricity for MCPA6, working as ponds to store PW. On the other hand, abundant cracks are found along carbon fibers, working as ditches to transport PW onto the rubbing surface. Thus, the ternary CF/N−RGO/PW 3D skeleton exhibits a pond and ditch structure for the efficient storage and transportation of PW. In comparison with the neat MCPA6, the friction coefficient and wear loss of MCPA6/CF/N−RGO/PW decline by (83 and 65) %, respectively. Theoretical calculations based on density functional theory support the efficient adsorption of PW onto N−RGO. Therefore, the as-prepared MCPA6/CF/N−RGO/PW composite herein provides a new reference to prepare polymer composites with advanced tribological performance on account of the novel strategy of the storage and transportation of lubricants. [Display omitted] • A novel CF/N-RGO/PW ternary skeleton was developed for advanced tribological performances of MCPA6. • The ternary skeleton exhibits a unique ponds and ditches structure. • The excellent tribological performances were attributed to the efficient storage and transport of PW. • Theorotical calculation comfirmed the adsorption of PW by N-RGO sheets. [ABSTRACT FROM AUTHOR]

A novel 3D nanocomposite of nitrogen doped Co-CNTs over graphene sheets (3D N-Co-CNT@NG) have been successfully fabricated via a simple, scalable and one-step thermal decomposition method. This 3D hierarchical nanostructure provides an admirable conductive network for effective charge transfer and avoids the agglomeration of NG matrices, which examine direct as well as non-enzymatic responses to glucose oxidation and H 2 O 2 reduction at a low potential. The novel electrode showed excellent electrochemical performance towards glucose oxidation, with high sensitivity of 9.05 μA cm −2 mM −1 , a wide linear range from 0.025 to 10.83 mM, and a detection limit of 100 nM with a fast response time of less than 3 s. Furthermore, non-enzymatic H 2 O 2 sensors based on the 3D N-Co-CNT@NG electrode exhibited high sensitivity (28.66 μA mM −1 cm −2 ), wide linear range (2.0–7449 μM), low detection limit of 2.0 μM (S/N=3), excellent selectivity, decent reproducibility and long term stability. Such outstanding electrochemical performance can be endorsed to the large electroactive surface area, unique porous architecture, highly conductive networks, and synergistic interaction between N-Co-CNTs and nitrogen doped graphene (NG) in the novel 3D nanocomposite. This facile, cost-effective, sensitive, and selective glucose as well as H 2 O 2 sensors are also proven to be appropriate for the detection of glucose as well as H 2 O 2 in human serum. [ABSTRACT FROM AUTHOR]

A novel hierarchical nanoporous thin film of AuPt alloy embedded in graphene (AuPt@GR) was successfully synthesized through the self-assembly of ultrafine AuPt nanoparticles (~3 nm) within GR sheets by means of a facile chemical vapor deposition (CVD) procedure without the use of any external organic capping agent and reducing agent. A binder-free sensor based on the AuPt@GR hybrid material was fabricated and its electrocatalytic activity was evaluated by using it to determine epinephrine (EP) in PBS solution (pH=7.4) and in human serum spiked PBS solution. Amperometric measurements of the sensor response showed an extremely low limit of detection (0.9 nM at a signal-to-noise ratio of 3), high sensitivity (1628 µA m M −1 cm −2 ), wide linear detection range (1.5×10 −9 –9.6×10 −6 M), and negligible response to interferents. At the same time, the sensor also exhibited very long-term amperometric stability (4000 s), cyclic voltammetric stability (500 cycles), good reproducibility, and highly accurate detection of EP in real samples. The excellent electrochemical performance was attributed to synergistic effects of Au, Pt, and GR as well as to the formation of a unique nanoporous structure that provided enhanced electrocatalytic activity, a highly electroactive surface, and fast mass transport. These results suggest strong potential of the AuPt@GR hybrids for use in biosensors and bioelectronic devices. [ABSTRACT FROM AUTHOR]

Heteroatom co-doped carbon-based materials have been demonstrated to be an effective way to realize their new functions in electrode materials for energy storage devices. Herein, a novel strategy for synthesis of highly porous nitrogen-sulfur co-doped graphene nanoribbons (NS-GNRs) with enhanced active sites was developed. The highly porous NS-GNR channels provide efficient ion transport path for electrolyte ions, which enhances the overall conductivity and stability of the electrode materials by energising storage sites. The TEM and STEM-EDS analysis revealed that the NS-GNR materials exhibit uniform distribution of N and S heteroatoms into GNRs matrices. The NS-GNR electrode materials exhibited a high specific capacitance of 442 F g −1 at 0.5 A g −1 , excellent rate capability and cycling performance with ∼98.6 % retention of the initial capacitance after 10,000 cycles. Most importantly, the fabricated symmetric supercapacitor device with a wide operating voltage window of ∼1.8 V yield an excellent energy density of ∼23.85 Wh kg −1 , high power density of ∼8753 W kg −1 and superior cycle life (97.9% capacitance retention after 10,000 cycles). Thus, these results exhibit a novel metal-free and low-cost design of electrode materials for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

In an effort to develop electrocatalysts associated with effective design, testing, and fabrication, novel porous gold-palladium nanoalloy network-supported graphene (AuPd@GR) nanohybrids were successfully synthesized via electroless deposition followed by a chemical vapor deposition (CVD) method for the first time. The AuPd@GR nanohybrids were obtained as a continuous, porous, transparent, bendable, and ultrathin film with good assembly of the AuPd nanoalloy particles (<10 nm) within the GR. The AuPd@GR nanohybrids exhibited excellent catalytic activity towards H 2 O 2 detection with a wide detection range (5 μM–11.5 mM), high sensitivity (186.86 μA mM −1 cm −2 ), low limit of detection (1 μM), fast response (3 s), and long-term working stability (2500 s). Furthermore, the AuPd@GR nanohybrids demonstrated outstanding durability, along with negligible interference from ascorbic acid, dopamine, uric acid, urea, potassium ions, chloride ions, and glucose. These findings open a new pathway to fabricate electrocatalysts for application in high performance electrochemical sensors and bioelectronics. [ABSTRACT FROM AUTHOR]

A novel gold nanoparticle-anchored nitrogen-doped graphene (AuNP/NG) nanohybrid was synthesized through a seed-assisted growth method, as an effective electrocatalyst for glucose and dopamine detection. The AuNP/NG nanohybrids exhibited high sensitivity and selectivity toward glucose and dopamine sensing applications. The as-synthesized nanohybrids exhibited excellent catalytic activity toward glucose, with a linear response throughout the concentration range from 40 μM to 16.1 mM, a detection limit of 12 μM, and a short response time (∼ 10 s). It also exhibited an excellent response toward DA, with a wide detection range from 30 nM to 48 μM, a low detection limit of 10 nM, and a short response time (∼ 8 s). Furthermore, it also showed long-term stability and high selectivity for the target analytes. These results imply that such nanohybrids show a great potential for electrochemical biosensing application. [ABSTRACT FROM AUTHOR]

Novel vanadium nitride/nitrogen-doped graphene (VN/NG) composite was fabricated and used as stable high performance anode materials for supercapacitors. The VN/NG composite anode material exhibited excellent rate capability, outstanding cycling stability, and superior performance. FE-SEM and TEM studies of VN/NG composite revealed that ultra-thin VN nanostructures were homogeneously distributed on flexible NG nanosheets. The NG provided a highly conductive network to boost the charge transport involved during the capacitance generation and also aided the dispersion of nanostructured VN within the NG network. The synergetic VN/NG composite exhibited an ultra-high specific capacitance of 445 F g −1 at 1 Ag −1 with a wide operation window (−1.2 to 0 V) and showed outstanding rate capability (98.66% capacity retention after 10,000 cycles at 10 Ag −1 ). The VN/NG electrode offered a maximum energy density (∼81.73 Wh kg −1 ) and an ultra-high power density (∼28.82 kW kg −1 at 51.24 Wh kg −1 ). The cycling performance of the VN/NG composite was superior to that of pure VN nanostructure. These finding open a new path way to the designated fabrication of VN/NG composite as anode materials in the development of high performance energy storage devices. [ABSTRACT FROM AUTHOR]

A facile and cost-effective one-pot solvothermal method has been successfully developed to synthesize an N-doped graphene (NG) and copper–nickel oxide (CuNiO) composite. The novel NG/CuNiO composite is proposed to be used as an electrode material for supercapacitors and non-enzymatic glucose sensors. Transmission electron microscopy images indicate the formation of CuNiO nanoparticles with an average diameter of approximately 5.6 nm, with good dispersion on the NG sheets. The composite exhibited an excellent specific capacity of ≈892 F g −1 (current density of 1 A g −1 ) and high long-cycle stability with a 98.5% retention in specific capacitance after 5000 cycles at a current density of 5 A g −1 . This superior electrochemical performance is attributed to high charge mobility, the flexibility of the N-doped graphene structure, and the synergetic effect between CuNiO nanoparticles and NG sheets. Further, the proposed sensor exhibited rapid response (<10 s), high sensitivity (7.49 μA mM −1 cm −2 ), a wide detection range (0.2 μM–0.3 mM), good reproducibility, long-term stability, and a low detection limit 50 nM ( S / N = 3). The NG/CuNiO composite electrode can be used for high performance supercapacitor and non-enzymatic glucose sensor applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] NiCo2O4 were grown on RGO by in-situ synthesis process. [•] FE-SEM image revealed self-assembled layer by layer growth of NiCo2O4-RGO nanocomposite. [•] NiCo2O4-RGO nanocomposite exhibited synergetic effects on its electrochemical performance. [ABSTRACT FROM AUTHOR]

Highlights: [•] Facile method for the preparation of SPG/AuNPs/chitosan nanocomposite. [•] The synergistic effect between graphene and AuNPs promotes the electro oxidation. [•] The GO x /SPG–AuNPs–CH/ITO bioelectrode is used for glucose sensor with negligible interference and long term stability. [ABSTRACT FROM AUTHOR]

Abstract: Ionic and non-ionic surfactant functionalized, water dispersible graphene were prepared to investigate the effects on the dispersion stability and electrical conductivity of graphene. In this study, sodium dodecyl benzene sulfonate (SDBS), sodium dodecyl sulfate and 4-(1,1,3,3-tetramethylbutyl) phenyl-polyethylene glycol (Triton X-100) were used as ionic and non-ionic surfactants. The effects of surfactant concentrations on the dispersibility and electrical conductivity of the surface modified graphene were investigated. The dispersion stability of SDBS functionalized graphene (SDBS-G) was found to be best in water at 1.5mgml−1. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy analysis indicate that the presence of surfactants does not prevent the reduction of graphene oxide (GO). These measurements also demonstrated that the surfactants were present on the surface of graphene, resulting in the formation of functionalized graphene. The thickness of different functionalized graphene was measured by Atomic force microscopy and varied significantly with different surfactants. The thermal properties of the functionalized graphene were also found to be dependent on the nature of the surfactants. The electrical conductivity of SDBS-G (108Sm−1) was comparatively higher than SDS and Triton X-100 functionalized graphene. [Copyright &y& Elsevier]

Abstract: Functionalization and dispersion of graphene sheets are of crucial importance for their end applications. Chemical functionalization of graphene enables this material to be processed by solvent-assisted techniques, such as layer-by-layer assembly, spin-coating, and filtration. It also prevents the agglomeration of single layer graphene during reduction and maintains the inherent properties of graphene. Therefore, a detailed review on the advances of chemical functionalization of graphene is presented. Synthesis and characterization of graphene have also been reviewed in the current article. The functionalization of graphene can be performed by covalent and noncovalent modification techniques. In both cases, surface modification of graphene oxide followed by reduction has been carried out to obtain functionalized graphene. It has been found that both the covalent and noncovalent modification techniques are very effective in the preparation of processable graphene. However, the electrical conductivity of the functionalized graphene has been observed to decrease significantly compared to pure graphene. Moreover, the surface area of the functionalized graphene prepared by covalent and non-covalent techniques decreases significantly due to the destructive chemical oxidation of flake graphite followed by sonication, functionalization and chemical reduction. In order to overcome these problems, several studies have been reported on the preparation of functionalized graphene directly from graphite (one-step process). In all these cases, surface modification of graphene can prevent agglomeration and facilitates the formation of stable dispersions. Surface modified graphene can be used for the fabrication of polymer nanocomposites, super-capacitor devices, drug delivery system, solar cells, memory devices, transistor device, biosensor, etc. [Copyright &y& Elsevier]

Abstract: The surface functionalization of graphene and the preparation of functionalized graphene/ethylene vinyl acetate co-polymer (EVA) composites by solution mixing are described. Octadecyl amine (ODA) was selected as a surface modifier for the preparation of functionalized graphene (ODA-G) in an aqueous medium. The ODA-G was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, which confirm the modification and reduction of graphite oxide to graphene. Atomic force microscopy shows that the average thickness of ODA-G is ca. 1.9 nm. The ODA-G/EVA composites were characterized by X-ray diffraction and transmission electron microscopy, which confirms the formation of ODA-G/EVA composites. Measurement of tensile properties shows that the tensile strength of the composites (with 1 wt.% ODA-G loading) is ∼74% higher as compared to pure EVA. Dynamic mechanical analysis shows that the storage modulus of the composites is much higher than that of pure EVA. The thermal stability of the composite with 8 wt.% of ODA-G is ∼42 °C higher than that of pure EVA. The electrical resistivity has also decreased in the composites with 8 wt.% of ODA-G. [Copyright &y& Elsevier]

Abstract: A green approach for the reduction of graphene oxide (GO) using wild carrot root is reported in this work. It avoids the use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain graphene. The endophytic microorganisms present in the carrot root, reduces exfoliated GO to graphene at room temperature in an aqueous medium. Transmission electron microscopy and atomic force microscopy images provide clear evidence for the formation of few layer graphene. Characterization of the resulting carrot reduced GO by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy shows partial reduction of GO to graphene. Raman spectroscopy data also indicates the partial removal of oxygen-containing functional groups from the surface of GO and formation of graphene with defects. [Copyright &y& Elsevier]

Abstract: Dodecyl amine-modified graphene (DA-G)/linear low density polyethylene (LLDPE) nanocomposites were prepared through solution mixing. Field emission scanning electron microscopy analysis revealed homogeneous dispersions of graphene layers in the nanocomposites. X-ray diffraction analysis showed that the average crystallite size of the nanocomposites was increased. However, the % crystallinity was found to decrease due to the formation of a random interface. Dynamic mechanical analysis showed that the storage moduli of the nanocomposites were much higher than that of neat LLDPE. The nanocomposites were also more thermally stable than neat LLDPE. Isothermal thermogravimetry showed that homogeneously distributed graphene could act as a good inhibitor during thermal degradation of the nanocomposites. Differential scanning calorimetry showed that the crystallization temperature of the nanocomposites increased with increasing DA-G content. Thermomechanical analysis showed that the dimensional stability of the nanocomposites was significantly increased by the addition of the DA-G. The coefficients of thermal expansion decreased with increasing DA-G content. The oxygen and nitrogen permeability of the nanocomposites was lower than that of neat LLDPE. [Copyright &y& Elsevier]

Abstract: A detailed overview towards the advancement of graphene based biosensors has been reviewed. The large surface area and excellent electrical conductivity of graphene allow it to act as an “electron wire” between the redox centers of an enzyme or protein and an electrode''s surface. Rapid electron transfer facilitates accurate and selective detection of biomolecules. This review discusses the application of graphene for the detection of glucose, Cyt-c, NADH, Hb, cholesterol, AA, UA, DA, and H2O2. GO and RGO have been used for the fabrication of heavy metal ion sensors, gas sensors, and DNA sensors. Graphene based FETs have also been discussed in details. In all these cases, the biosensors performed well with low working potentials, high sensitivities, low detection limits, and long-term stabilities. [Copyright &y& Elsevier]

Abstract: The surface modification of graphene as well as the characterization of modified graphene-based polymer composite prepared by solution mixing techniques was examined. X-ray photoelectron spectroscopy was employed to examine the surface modification and formation of graphene. The tensile strength of the composite increased with 3 wt.% of DA-G loading and was 46% higher than that of neat LLDPE. The onset thermal degradation temperature of the composite (3 wt.% of DA-G) was increased by ∼40°C compared to neat LLDPE. A sharp increase in electrical conductivity of the composite was observed at 3 wt.% of DA-G content. [Copyright &y& Elsevier]

Abstract: Polypyrrole (PPy)/graphene (GR) nanocomposites were successfully prepared via in-situ polymerization of graphite oxide (GO) and pyrrole monomer followed by chemical reduction using hydrazine monohydrate. The large surface area and high aspect ratio of the in-situ generated graphene played an important role in justifying the noticeable improvements in electrical conductivity of the prepared composites via chemical reduction. X-ray photoelectron spectroscopy (XPS) analysis revealed the removal of oxygen functionality from the GO surface after reduction and the bonding structure of the reduced composites were further determined from FTIR and Raman spectroscopic analysis. For PPy/GR composite, intensity ratio between D band and G band was high (∼1.17), indicating an increased number of c-sp2 domains that were formed during the reduction process. A reasonable improvement in thermal stability of the reduced composite was also observed. Transmission electron microscopy (TEM) observations indicated the dispersion of the graphene nanosheets within the PPy matrix. [ABSTRACT FROM AUTHOR]

Abstract: This paper reviews recent advances in the modification of graphene and the fabrication of graphene-based polymer nanocomposites. Recently, graphene has attracted both academic and industrial interest because it can produce a dramatic improvement in properties at very low filler content. The modification of graphene/graphene oxide and the utilization of these materials in the fabrication of nanocomposites with different polymer matrixes have been explored. Different organic polymers have been used to fabricate graphene filled polymer nanocomposites by a range of methods. In the case of modified graphene-based polymer nanocomposites, the percolation threshold can be achieved at a very lower filler loading. Herein, the structure, preparation and properties of polymer/graphene nanocomposites are discussed in general along with detailed examples drawn from the scientific literature. [Copyright &y& Elsevier]