Fe3O4@carbon nanosheet composites were synthesized using ammonium ferric citrate as the Fe3O4/carbon precursor and graphene oxide as the structure-directing agent under a hydrothermal process. The surface chemical compositions, pore structures, and morphology of the composite were analyzed and characterized by nitrogen adsorption isotherms, TG analysis, FT-IR, X-ray photoelectron energy spectrum, transmission electron microscopy, and scanning electron microscopy. The composites showed excellent specific capacitance of 586 F/g, 340 F/g at 0.5 A/g and 10 A/g. The all-solid-state asymmetric supercapacitor device assembled using carbon nanosheets in situ embedded Fe3O4 composite and porous carbon showed a largest energy density of 18.3 Wh/kg at power density of 351 W/kg in KOH/PVA gel electrolyte. The synergism of high special surface to volume ratio, mesoporous structure, graphene-based conduction paths, and Fe3O4 nanoparticles provided a high surface area of ion-accessibility, high electric conductivity, and the utmost utilization of Fe3O4 and resulted in excellent specific capacitance, outstanding rate capability and cycling life as all-solid-state supercapacitor electrodes.

Carbon nanosheets (CNSs) with tunable sizes, morphologies, and pore structures have been synthesized through several chemical routes. Graphitized CNSs have been synthesized through exfoliation, chemical vapor deposition, or high-temperature carbonization. Porous CNSs have been synthesized by using various methods, including pyrolysis, self-assembly, or a solvothermal method in connection with carbonization. These CNSs have successfully been used as detectors for metal ions, as cathodes for field electron emissions, as electrodes for supercapacitors and fuel cells, and as supports for photocatalytic and catalytic oxygen reduction. Therefore, the synthesis and application of CNSs are receiving increasing levels of interest, particularly as application benefits, in the context of future energy/chemical industry, are becoming recognized. This review provides a summary of the most recent and important progress in the production of CNSs and highlights their application in environmental and energy-related fields.

No abstract

Iron (Fe)- and nitrogen (N)-codoped carbon materials hold broad application prospects in the oxygen reduction reaction (ORR) because of their abundant reserves, low cost, and excellent catalytic activity. In this study, a N-doped carbon nanotube (CNT)–graphene framework with encapsulated Fe/Fe3N nanoparticles (Fe–N–CNT@RGO) is designed and synthesized by annealing a mixture of iron acetylacetonate, dicyandiamide, and graphene oxide via a one-step calcination strategy. Fe–N–CNT@RGO has a better ORR catalytic activity than reduced graphene oxide (RGO), N-doped graphene, and N-doped CNTs with encapsulated Fe/Fe3N nanoparticles with respect to the onset potential, limiting current density, and kinetic current density. Fe–N–CNT@RGO also has high stability and a high discharging cell voltage, which approaches those of platinum/carbon in zinc–air batteries. The relationship between the structure and activity of Fe–N–CNT@RGO demonstrates that the high density of Fe–N and pyridinic N sites, moderate wettability, and positive ζ potential promote exposure of the active sites, accelerate the transmission of hydrated oxygen, and enhance the adsorption of HO2 – for the 4e– ORR.

No abstract

No abstract

No abstract

Microporous carbons nanosheets with controllable thicknesses were synthesized using gelatin biomass as both carbon and nitrogen precursors and graphene oxide (GO) without any auxiliary reagent. The pore structures, surface chemical compositions, and morphology of the microporous carbon material were analyzed and characterized by nitrogen adsorption isotherms, thermogravimetric analysis, Fourier transform infrared spectrum, X-ray photoelectron energy spectrum, and transmission electron microscope and scanning electron microscope images. The carbon nanosheets showed average thicknesses from 10 ± 4 to 30 ± 8 nm with tuning mass ratios of gelatin to GO from 20/1 to 100/1. The microporous carbon nanosheets exhibited high specific capacitance and excellent rate capability with a capacitance retention of 76% at 20 A/g in a 6 mol/L KOH aqueous electrolyte because of the shorter diffusion distance, large surface area, and excellent electrical conductivity.