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ABSTRACT Carbon nanomaterials (CNMs) have been proposed as promising nanofillers for polymer composites because of their high surface area, structural flexibility, good mechanical strength, and their unique thermal, optical, and electronic properties. However, the strong van der Waals interactions between individual nanoparticles have limited the manipulation of CNMs and restricted their use in many promising fields. The functionalization of CNMs has attracted great interest on synthesis of complex structures, and helped establish different facile, scalable, controllable and low-cost methods to graft well-defined polymers onto the surfaces of CNMs. This review highlights the advances made in recent years on the functionalization chemistry of carbon nanotubes and graphene with polymers by both the ' grafting from' and ' grafting to' techniques. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 622-631 [ABSTRACT FROM AUTHOR]

The use of reduced graphene oxide (rGO) in high-temperature oxidization (HTO) environment, is limited by its poor thermal oxidation and fire resistance. In this study phosphorus and nitrogen co-doped reduced graphene oxide (PN-rGO) with high oxidation and fire resistance was prepared by hydrothermal and microwave treatment and its thermal oxidation decomposition kinetics and mechanisms were analyzed. Concisely, PN-rGO presents an increment of 162 °C in the decomposition temperature relative to undoped rGO (WrGO), and excellent fire resistance with only a ∼20% mass loss after burning. Thermal oxidation degradation kinetics reveals that WrGO shows continuously increasing activation energy (E) within a range of 119.7–182.9 kJ/mol, while PN-rGO exhibits almost constant E of ∼171.8 kJ/mol during main degradation stage. Moreover, the improved E at initial stage by phosphorus/nitrogen doping, combining with the char analysis, suggested that the introduction of strong chemical bonds replacing the reactive oxygen-containing groups was the key to preventing the oxidation of rGO. As one of the main properties, the electrical conductivity of PN-rGO is well kept after HTO treatment. This work demonstrates that a doping strategy can effectively expand the application of graphene-based devices in HTO environment. Image 1 [ABSTRACT FROM AUTHOR]

Abstract Metal compound/graphene composites have been dominantly fabricated by in-situ intercalation of metal-containing precursors into graphene or graphene oxide (GO) followed by chemical and/or thermal treatment. This process usually leads to the formation of 0D oxide nanoparticles/2D graphene composites with the limited improvements in the supercapacitor performance. Herein a facile two-step method was reported to fabricate 3D porous Ni(OH) 2 /graphene composite hydrogels (NiGH) by incorporating the pre-synthesized 1D Ni(OH) 2 nanobelts into a GO suspension followed by the hydrothermal process. The resulted hydrogels show large specific surface area (370.6 m2/g) and can be directly used as the self-supported electrodes. The NiGH electrode exhibits the specific capacitance up to 1738.3 F/g at 10 mV/s and 1701.5 F/g at 1 A/g, retains 1385.0 F/g at 100 mV/s and 1152.0 F/g at 8 A/g, respectively. The capacitance and rate performance of NiGH are far superior to those of Ni(OH) 2 (841.2 F/g at 10 mV/s; 592.5 F/g at 1.0 A/g), graphene hydrogel (207.5 F/g at 10 mV/s), and the control Ni(OH) 2 nanoparticle/graphene composite powder (NiGP: 1045.8 F/g at 10 mV/s; 950.8 F/g at 1.0 A/g) prepared by the one-pot hydrothermal processing of Ni salt and GO. Meanwhile, the NiGH electrode also shows lower resistance and higher cycling stability (retaining 100.8% of initial capacitance over 5000 cycles at 5 A/g) as compared to Ni(OH) 2 , graphene hydrogel, and NiGP due to the efficient combination of pseudo-capacitive 1D Ni(OH) 2 nanobelts and conductive 2D graphene sheets to create 3D architectures. Such a facile two-step protocol enables the superiority of ultrathin oxide nanobelts to fabricate 3D graphene-based composite hydrogels for high-performance supercapacitor electrodes. Graphical abstract 3D Ni(OH) 2 nanobelt/graphene composite hydrogels were fabricated by incorporating the pre-synthesized Ni(OH) 2 nanobelts into a suspension of graphene oxide followed by hydrothermal treatment. The resulting self-supported electrodes show much better electrochemical performance compared to the powdery Ni(OH) 2 nanoparticle/graphene composites prepared by one-pot hydrothermal processing of Ni salts and graphene oxide. Image 1 Highlights • Combining quasi-1D Ni(OH) 2 nanobelts with 2D graphene to fabricate 3D hydrogels. • Free-standing electrodes with large specific surface area and ultrahigh capacitance. • Synergistic improvements in rate capability, interface resistance, and cyclability. [ABSTRACT FROM AUTHOR]

Phosphorus and/or nitrogen doping is an effective method of improving the physical and chemical properties of reduced graphene oxide (rGO). In this work, phosphorus and nitrogen co-doped rGO (PN-rGO), synthesized using a scalable hydrothermal and microwave process, was used as an additive to improve the flame retardancy of epoxy resin (EP) for the first time. Chemical structure and morphology characterization confirmed that the nitrogen and phosphorus atoms were doped into the graphite lattice adopting pyrrolic-N, pyridinic-N, quaternary-N and pyrophosphate and metaphosphate forms. Doping increased the oxidization resistance of rGO and the thermal-oxidative stability of its composites’ char, while also improving the catalytic charring ability of polymer. Both effects resulted in the formation of a stable char protective layer during burning and to a significant improvement in flame retardation and smoke suppression in the final composites. The peak heat release rate (PHRR), total heat release (THR) and total smoke production (TSP) for the EP-based composite (containing 5 wt% PN-rGO) decreased by 30.9%, 29.3% and 51.3%, respectively, compared to neat EP. Our work has produced a promising graphene-based flame retardant additive for the mass production of high-performance composites, also expended the application of heteroatom-doped graphene. [ABSTRACT FROM AUTHOR]

A bioinspired Co 3 O 4 /graphene composite film was fabricated by an electrostatic self-assembly of poly(diallyldimethylammonium chloride)-stabilized porous Co 3 O 4 flakes and graphene oxide nanosheets under vacuum filtration-induced directional flow in combination with subsequent thermal annealing. The resulting composite film was then empolyed as a self-supported electrode for supercapacitors. The narce-like layered architecture allows for an intimate interface contact and strong interactions between the two. This ensures a large ion-accessible surface and high structural integrality of the electrode during charging-discharging cycles. The high porosity of Co 3 O 4 is capable of affording short diffusion paths of charges and high electrochemical utilization of the electrode. Graphene sheets also construct a highly-conductive platform for fast charge transport and electrochemical reactions. Such unique bioinspired morphology and synergistic effects between porous Co 3 O 4 flakes and graphene sheets promise excellent electrochemical performance. As expected, the free-standing electrode exhibits a specific capacitance of 623.8 F/g at a scan rate of 5 mV/s, and retains 83% of initial capacitance in the current density increasing from 1.0 to 8.0 A/g, suggesting large energy storage and high rate capabilities. The retention of initial capacitance remains 87% after 1000 cycles at 20 mV/s, indicating excellent cycling stability and reversibility. [ABSTRACT FROM AUTHOR]

Silver-doped graphene/MnO 2 (SGM) hierarchical composites were readily fabricated by silver-ion-assisted room-temperature catalytic growth of urchin-like MnO 2 spheres from the surface of graphene oxide (GO) followed by chemical reduction. This in-situ crafting strategy allows us to control the size of MnO 2 spheres by tuning the concentration of silver ions in the reaction mixture. Graphene herein functions as a separator to prevent the agglomeration of MnO 2 and a wrapper around MnO 2 to avoid the electrochemical dissolution during charging/discharging cycles. MnO 2 spheres grown from the surface of GO sheets ensure an intimate interface contact and large interface area between the two, and also prevent the stacking of graphene, thus affording open channels, high accessible surface, short diffusion paths of charges and high electrochemical utilization of the electrode. Furthermore, graphene sheets bridge a robust conductive network which facilitates fast transport of electrolyte ions and electrons throughout the electrode. As expected, an optimized SGM composite electrode delivers a much higher specific capacitance (∼273.1 F g −1 at 5 mV s −1 , and ∼260 F g −1 at 0.2 A g −1 ) compared to the reduced GO (119.4 F g −1 ) and MnO 2 (140.9 F g −1 ) counterparts. The retention of initial capacitance reaches 77.8% after a 20-fold increase in the scan rate, and remains 83.5% after 1200 cycles, indicating high rate capability and excellent cyclability. [ABSTRACT FROM AUTHOR]

Direct reduction of graphene oxide (GO) to graphene often results in an irreversible agglomeration and hence suppressing its effective surface available for energy storage. In this work, GO was solvothermally reduced in the presence of imidazolium-based poly(ionic liquid) (PIL) of poly(1-butyl-3-vinylimidazolium hexafluorophosphate) to produce a PIL-modified reduced GO (PIL-rGO) composite. The integration of PILs with rGO is capable of preventing the restacking of rGO sheets, and hence, providing a large electrolyte ion-accessible surface and an abundant interior space for charge storage by enlarging the interlayer spacing in PIL-rGO. The PIL-rGO composite was then used as the supercapacitor electrode associated with a compatible IL of 1-butyl-3-methylimidazolium hexafluorophosphate as the electrolyte. The PIL herein improves the interface wettability between the electrode and electrolyte, and the IL electrolyte enables a wide potential window as well. Specific capacitances correspond to 196 F/g at a current density of 1 A/g, 160 F/g at 2 A/g, and 144.8 F/g at a scan rate of 60 mV/s, which are much higher than those (104 F/g at 2 A/g, and 48.1 F/g at 60 mV/s) of pure rGO. The capacitance retention is as high as 80.7% after 1000 charge-discharge cycles at a discharge current density of 2 A/g. The interfacial charge-transfer resistance of the PIL-rGO electrode (4.6 Ω) is also much lower than that of the rGO electrode (18.7 Ω). Such graphene-base electrodes may promise a candidate for high performance supercapacitors. [ABSTRACT FROM AUTHOR]