Phosphorus, nitrogen and oxygen co-doped polymer-based core-shell carbon sphere for high-performance hybrid supercapacitors

Co-doping heteroatoms of the carbon lattice has been proven as an efficient strategy that can improve the capacitive performance, due to the synergetic effect of several dopants. Herein, a series of phosphorus, nitrogen and oxygen, co-doped polymer-based carbon spheres were prepared by the suspension polymerization method and chemical activation with phosphoric acid at different temperatures. The presence of heteroatoms was confirmed by X-ray photoelectron spectroscopy and elemental analysis. The structure of the carbons was characterized by scanning electron microscopy, Raman spectroscopy and nitrogen adsorption. Carbon obtained at 800 degrees C with a P, N and O doping level of 11.17 at%, 2.79 at% and 11.77 at% respectively, shows a capacitance of 157 F g(-1) at the current density of 0.05 A g(-1). Moreover, the electrode can survive at a wide potential window of 1.5 V with only 15% decrease in capacity after 10000 cycles at a current density of 5 A g(-1), providing a high energy density of 10 Wh kg(-1) and a high power density of 750 W kg(-1). For the outstanding features, it is expected that the phosphorus, nitrogen and oxygen co-doped carbons will be a very suitable material not only for supercapacitors, but also for lithium batteries and oxygen reduction reaction. In addition, the co-doping method described here might be extended to the preparation of other kinds of porous carbon materials. (c) 2018 Elsevier Ltd. All rights reserved

The polymer blend technique as a method for designing fine carbon materials

The polymer blend technique is proposed as a method for designing fine carbon materials. In principle a blend consisting of polymers with and without carbon residue after heating is subjected to melt-spinning, stabilization and finally carbonization. A combination of two polymers and control of the blend texture are important for using the technique successfully. In this paper, three prepared fine carbon materials are introduced, i.e. carbon fibers including thin and long pores aligned parallel to the fiber, thin carbon fibers 200-300 nm in diameter and carbon nanotubes with 10-20-nm outer diameter. In particular the carbon nanotubes are described in detail to emphasize the great potential of the polymer blend technique. Further possibilities of the technique are also discussed briefly. (C) 2003 Elsevier Science Ltd. All rights reserved

Poly(vinylidene fluoride) as a porogen to prepare nitrogen-enriched porous carbon electrode materials from pyrolysis of melamine resin

Nitrogen-enriched carbons with hierarchical pore structures were prepared by the direct pyrolysis of melamine resin and poly(vinylidene fluoride) (PVDF) in an inert atmosphere. Our preparation method produced carbons that feature high micropore surface areas of up to 966 m(2) g(-1), with the peak micropore width around 0.5-0.6 nm, and 3-4 nm mesopore channels without the need for a template or activation post-carbonization. The carbons were characterized using N-2 and CO2 sorption analyses, X-ray photoelectron spectroscopy and elemental analysis. The concentrations of nitrogen at the carbon surface were in the range 3.1-4.5 at.%. The electrochemical performance of carbon electrodes was evaluated using cyclic voltammetry, galvanostatic charge-discharge techniques and impedance spectroscopy in 1 MH2 SO4 and 1 M TEABF(4)/acetonitrile. Electrochemical tests in aqueous electrolyte showed excellent rate performance with capacitive behaviour up to 500 mV s(-1) and a specific capacitance of 125 F g(-1) at the current density of 0.05 A g(-1) in a two-electrode cell. In both aqueous and organic electrolytes, good cycling performance are obtain with 96% and 77% of the initial capacitance after 10,000 and 5000 cycles, respectively. (C) 2015 Elsevier Ltd. All rights reserved

Heteroatom-doped graphene for electrochemical energy storage

The increasing energy consumption and environmental concerns due to burning fossil fuel are key drivers for the development of effective energy storage systems based on innovative materials. Among these materials, graphene has emerged as one of the most promising due to its chemical, electrical, and mechanical properties. Heteroatom doping has been proven as an effective way to tailor the properties of graphene and render its potential use for energy storage devices. In this view, we review the recent developments in the synthesis and applications of heteroatom-doped graphene in supercapacitors and lithium ion batteries

Carbon nanotubes prepared from three-layered copolymer microspheres of acrylonitrile and methylmethacrylate

Carbon nanotubes (CNTs) were synthesized from fine three-layered copolymer microspheres using the polymer blend technique. Diameter of PMMA core/Poly(AN-co-MMA) shell-1/PMMA shell-2 microspheres, prepared by a radical soap-free emulsion polymerization of methylmethacrylate (MMA) and acrylonitrile (AN), was between 400 nm and 500 nm. Microspheres were subjected to melt-spinning at 305 degrees C, stabilizing in oxygen at 220 degrees C for 4 h, and finally carbonizing at 1000 degrees C for 30 min. FE-SEM study of carbonized sample revealed the presence of CNTs arrays on carbon blocks. Similar arrays were observed in a comparative CNTs sample prepared from three-layered microspheres with the pure PAN shells-1 layers. HRTEM showed that the CNTs derived from copolymer microspheres had different structure when compared to the control sample, i.e. CNTs often adhered to each other and contained the internal compartments. The insufficient PMMA shell-2 coating of copolymer microspheres is believed to be a reason for CNTs adhesion. The possible mechanisms of the carbon block formation and the adhesion of CNTs are introduced. (c) 2005 Elsevier Ltd. All rights reserved

Nanorods of vanadium compounds: synthesis, characterisation, and application in electrochemical energy storage

The synthesis and characterisation of nanorods of vanadium pentoxide, V(2)O(5), vanadium trioxide, V(2)O(3), vanadium dioxide, VO(2)(B), and vanadium nitride, VN, are presented, and their application in electrochemical supercapacitors and lithium-ion batteries is outlined. Specifically, a novel method for the preparation of V(2)O(5) nanorods is discussed. It involves ball milling as a first step and controlled annealing as a second step. Nanorods of V(2)O(5) can be converted into those of other vanadium-related phases by simple chemical reduction treatments. Such chemical transformations are pseudomorphic and often topotactic, that is, the resulting nanorods belong to a different chemical phase but tend to retain the original morphology and preferential crystal orientation dictated by parent V(2)O(5) crystals. The corresponding properties of nanorods for their prospective application in electrochemical energy storage (lithium-ion batteries and electrochemical supercapacitors) are discussed. The synthesised V(2)O(5) nanorods possess a stable cyclic behaviour when they are used in a cathode of a lithium-ion battery and are suitable for use in an anode. VN nanorods synthesised by NH(3) reduction of V(2)O(5) were found to possess pseudocapacitive properties in aqueous electrolytes. <br /