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Hierarchically structured carbon nanofiber/graphene/MnO 2 (CGMn) hybrid with oxygen and nitrogen functionalities was fabricated in the form of a web via electrospinning as an electrode material for supercapacitors. The CGMn electrode exhibited a high capacitance (225 Fg −1 at 1 mAcm −2 ), enhanced energy and power efficiency (15.8–13.6 Whkg −1 in the power density range of 197–4000 Wkg −1 ), and excellent capacitance retention (13% of the initial value at a discharge current of 20 mAcm −2 ) in a 6 M KOH aqueous electrolyte, because of the combination of the double-layer capacitance and the pseudocapacitive character associated with the surface redox-type reactions. The porosity and the number of heteroatoms of the CGMn composite were adjusted by changing the PMMA concentration and carbonization temperature. Therefore, the oxygen- and nitrogen-containing hierarchical porous CGMn hybrid prepared by a simple method is a promising candidate as an electrode material for supercapacitors. [ABSTRACT FROM AUTHOR]

Herein, we demonstrate improvements to the compressive strength of cementitious mortar by incorporating rice husk-derived graphenes (GRHs). Several manufacturing trials were undertaken to synthesize optimized GRHs using different dosages of rice husk ash and potassium hydroxide as well as a range of activation temperatures. The incorporation of GRHs into mortar exhibits a generally enhanced reinforcing effect compared to graphene nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWNTs) because of its high specific surface area. SEM/TEM image analyses confirm that GRH has a corrugated graphene structure and clean edges at the atomic scale. GRH showed extremely high BET surface area (2274 m 2 /g) compared to those of multi-walled carbon nanotubes and GNPs (50–200 m 2 /g). [ABSTRACT FROM AUTHOR]

An effective way of covalently functionalizing graphene with a chitosan polymer via a nitrene chemistry is demonstrated. The biofunctionalized graphene is prepared by the chemical reduction of graphene oxide using a nitrene chemistry, and then covalently grafting chitosan to the graphene surface. The effectiveness of the biofunctionalized graphene as a reinforcing filler (4 wt%) in a chitosan polymer matrix is verified by the dramatic enhancement of the mechanical properties (breaking stress = 330%, Young's modulus = 243%) and the electrical conductivity (0.3 S m−1) without much loss in the elongation-at-break. The reinforcing effect can be explained by both the homogeneous dispersion of graphene within the matrix and the strong bond arising from the intrinsically intimate contact between the graphene and the matrix. The high antimicrobial activity of the biofunctionalized graphene compared with graphene oxide and chemically reduced graphene may be because of the presence of chitosan polymer on the edges of the graphene. The strong, antimicrobial graphene-filled composite film can be used for food packaging and for coating various biomedical devices, where bacterial surface colonization is undesirable. [ABSTRACT FROM AUTHOR]

An effective way of covalently functionalizing graphene with a biopolymer via nitrene chemistry is demonstrated by Yoong Ahm Kim, Jae Whan Cho, and co‐workers on page 721. The mechanical and electrical properties of the biocomposite film are tuned by varying the content of functionalized graphene. The high antimicrobial activity of the biofunctionalized graphene may be due to the presence of biopoly mer on edges of the graphene. [ABSTRACT FROM AUTHOR]

Coupling graphene-based materials with SiC nanostructures is one of the most feasible strategies to improve the photocatalytic CO 2 reduction performance. Here, we synthesized the vertical graphene (VG) sheets on the SiC nanowires achieved from rice husks to form the VG@SiC/C composite, in which the VG sheets possess high surface area, excellent electrical conductivity, and chemical stability, and the SiC nanowires have a suitable bandgap for sunlight absorption. The resulting VG@SiC/C composite provides an enhanced photocatalytic reduction of CO 2 to CO and CH 4 , yielding CO and CH 4 evolution yields of 25.5 and 2.3 μmol g−1 h−1, respectively. The achieved CO yield is maximal so far among the SiC-based photocatalysts. The defective VG sheets promote the absorption of sunlight, enhance the CO 2 adsorption and activation, increase the separation of photogenerated electron-hole pairs, improve the activity of photocatalyst, and thereby prompt the photocatalytic reduction of CO 2 to CO with high yield and selectivity. We report that the vertical graphene sheets on the surface of rice-husk-derived SiC/C composite demonstrate the enhanced photocatalytic performance of CO 2 reduction to CO with high yield and selectivity under simulated solar irradiation. [Display omitted] • The VG sheets could be achieved on the surface of rice-husk-derived SiC to form the VG@SiC/C. • The superior photocatalytic CO 2 performance was ascribed to the special structure and features of VG@SiC/C. • The VG can prompt the sunlight absorption, the CO 2 adsorption and activation, and the separation of electron-hole pairs. • The VG@SiC/C showed photocatalytic reduction of CO 2 with a CO yield of 25.5 μmol g−1 h−1 and a selectivity of 91.84%. [ABSTRACT FROM AUTHOR]

Vertical graphene (VG) sheets, which consist of few-layer graphene vertically aligned on the substrate with three-dimensionally interconnected porous network, make them become one of the most promising energy storage electrodes, especially for SCs. Nevertheless, the intrinsic hydrophobic nature of pristine VG sheets severely limited its application in aqueous SCs. Here, electrochemical oxidation strategy is adopted to increase the hydrophilicity of VG sheets by introducing oxygen functional groups so that the aqueous electrolyte can fully be in contact with the VG sheets to improve charge storage performance. Our work demonstrated that the introduction of oxygen functional groups not only greatly improved the hydrophilicity but also generated a pseudocapacitance to increase the specific capacitance. The resulting capacitance of electrochemically oxidized VG for 7 min (denoted as EOVG-7) exhibited three orders of magnitude higher (1605 mF/cm2) compared to pristine VG sheets. Through assembled two EOVG-7 electrodes, a symmetric supercapacitor demonstrated high specific capacitance of 307.5 mF/cm2, high energy density of 138.3 μWh/cm2 as well as excellent cyclic stability (84% capacitance retention after 10000 cycles). This strategy provides a promising way for designing and engineering carbon-based aqueous supercapacitors with high performance. The electrochemical oxidation strategy is adopted to increase the hydrophilicity of VG sheets by introducing oxygen functional groups so that the aqueous electrolyte can fully be in contact with the VG sheets to enhance electrochemical charge storage performance. The introduction of oxygen functional groups not only greatly improved the hydrophilicity but also generated a pseudocapacitance to increase the specific capacitance, further improve the energy density. [Display omitted] • Electrochemical oxidation method can significantly increase the functional groups on the surface of VG. • The hydrophilicity and additional pseudocapacitance are generated on surface-functionalized VG. • The optimized oxygen functional groups of VG surface can improve capacitance. • The symmetric SC shows excellent energy density (138.3 μWh/cm2), long-term cycle stability (84 %) and voltage of 1.8 V. [ABSTRACT FROM AUTHOR]

In the fabrication of safe, but powerful lithium ion batteries (LIBs), graphene-related materials are being actively examined in order to meet the demand for applications such as electric vehicles and smart grids. However, most of this work has focused on liquid-phase exfoliated graphene and reduced graphene oxide. Herein, we demonstrate a simple, but effective route for significantly improving the electrochemical performance of currently available LIBs by coupling current collector with catalytically grown large-area graphene. When coating current collectors with large-area three-layered graphene, a reduction in the internal resistance (or effective electron transfer) between the current collector and active materials was observed. The graphene also protected the underlying collector from corrosion, greatly improving the power capability and cyclability of LIBs. The three-layered graphene provided the best electrochemical performance and corrosion resistance because of its high electrical conductivity and mechanical stability during the transfer process. We believe that our approach using interfacial graphene coating can be used with all kinds of electrochemical energy-storage systems, in which high corrosion resistance, electrical conductivity, and flexibility are critical. Image 1 [ABSTRACT FROM AUTHOR]

Due to the special three-dimensional structures and excellent physicochemical properties, vertical graphene (VG) has been extensively investigated as potential material for supercapacitors. However, achieving VG-based supercapacitors with high-energy density and high-power density is a still tremendous challenge. Here we attempt to synthesize large-scale VG films on flexible substrates and design a novel battery-like supercapacitor (BSCs) with the VG on Ni foil (VG@Ni) as a binder-free electrode operating in the KOH electrolyte with the redox additives of K 3 Fe(CN) 6 and/or K 4 Fe(CN) 6. The VG@Ni electrodes demonstrate an ultrahigh areal capacitance of 1453 mF cm−2 at 5 mA cm−2 in 1 M KOH electrolyte with adding 0.07 M K 3 Fe(CN) 6 and 0.07 M K 4 Fe(CN) 6 , coulombic efficiency greater than 90%, and long-life cycling stability (capacitance retention is 99.3% after 20000 charge-discharge cycles). The BSCs, which are assembled with two identical VG@Ni electrodes, deliver the areal capacitance of 231 mF cm−2 with energy density of 32 μWh cm−2 and power density of 2498 μW cm−2 at 1 mA cm−2. These outstanding performances can be ascribed to the special feature and excellent properties of VG materials, high electronic conductivity of binder-free VG@Ni electrode, faradaic properties of redox electrolyte, and synergistic effects between the VG film and redox electrolyte. • Large-scale VG films are obtained on nickel and graphite foils by PECVD technique. • The VG films present excellent electrochemical performance in redox electrolyte. • The VG-based BSCs show high energy and power densities as well as long stability. [ABSTRACT FROM AUTHOR]

We explored the thermal performance, bond strength, and freeze-and-thaw resistance of mortar composite incorporating rice husk-derived graphene-like material (GRH). These three features are key for road pavement application, especially against ice and snow on its surface. Groups of GRH mortar prisms (20 × 20 × 50 mm, 50 × 50 × 100 mm) were tested to examine heating and cooling performance, in comparison with other carbon-based materials: multi-walled CNT, graphene platelets, and carbon fibers. Additionally, thermal performance was assessed in terms of GRH wt% insertion. GRH cubes of 50 mm with different wt% were tested to capture freeze-and-thaw resistance for 300 cycles. XRD, Rietveld, and SEM-EDS analyses of calcium silicate hydrate (CSH) gels of undamaged/damaged cubes with/without GRH were compared at the age of 120 days after casting. A group of Φ 100 × 200 mm slanted concrete cylinders was tested with a 10-mm-thick overlay with different wt% GRH. The compressive failure load and fractured area were used to evaluate the bond strength of the GRH thin overlay. [ABSTRACT FROM AUTHOR]

[Display omitted] • Porous S-doped graphene was prepared by the chemical vapor deposition of thiophene. • Effects of S-doping on supercapacitor electrode performance were investigated. • Electrochemical performance of porous S-doped graphene was enhanced by S-doping. • S-doping increased the electrical conductivity, wettability, and pseudocapacitance. In this study, we successfully synthesized porous S-doped graphene spheres (SGSs) with an S content of 1.1 at% by chemical vapor deposition on a spherical layered double hydroxide (LDH) template using thiophene (C 4 H 4 S) as the S-containing carbon source. The doped S atoms were removed from the SGSs by heat treatment under a H 2 atmosphere to give desulfurized graphene spheres (De-SGSs) that retained the original pore structure. The effects of the S-doping on the electrochemical behavior of the SGS supercapacitor electrode were investigated by comparing these behaviors with those of the De-SGS electrode. The results revealed that the SGS electrode exhibited electrical conductivity and surface wettability with the electrolyte that were superior to those of the De-SGS electrode. Furthermore, the SGS electrode showed an extremely high capacitance retention of approximately 100% at a current density of 20 mA cm−2 in an electrolyte of 1 M tetraethylammonium tetrafluoroborate in propylene carbonate (TEABF 4 /PC), while that of the De-SGS electrode under same conditions was approximately 40%. Thus, due to its excellent electrical conductivity, wettability, and the pseudocapacitive contribution of its S-dopants, the SGS electrode demonstrates an electrochemical performance that is superior to that of the De-SGS electrode. [ABSTRACT FROM AUTHOR]