Guofu Ma

Nitrogen-doped porous carbon derived from biomass waste for high-performance supercapacitor.

High capacitance property and low cost are the pivotal requirements for practical application of supercapacitor. In this paper, a low cost and high capacitance property nitrogen-doped porous carbon with high specific capacitance is prepared. The as-prepared nitrogen-doped porous carbon employing potato waste residue (PWR) as the carbon source, zinc chloride (ZnCl2) as the activating agent and melamine as nitrogen doping agent. The morphology and structure of the carbon materials are studied by scanning electron microscopy (SEM), N2 adsorption/desorption, X-ray diffraction (XRD) and Raman spectra. The surface area of the nitrogen-doped carbon which prepared under 700°C is found to be 1052m(2)/g, and the specific capacitance as high as 255Fg(-1) in 2M KOH electrolyte is obtained utilize the carbon as electrode materials. The electrode materials also show excellent cyclability with 93.7% coulombic efficiency at 5Ag(-1) current density of for 5000cycles.

High-performance supercapacitor based on multi-structural CuS@polypyrrole composites prepared by in situ oxidative polymerization

We have developed a supercapacitor electrode composed of CuS microspheres with polypyrrole (PPy) uniformly inserted into the sheet-like subunit structure and coated onto the CuS surface to enhance the pseudocapacitive performance. Novel sphere-like CuS particles with intertwined sheet-like subunit structure are fabricated by a solvothermal approach without any surfactant or template. A CuS@PPy composite electrode is prepared by in situ oxidation polymerization of pyrrole in the presence of the CuS suspension. The CuS@PPy composite (CuS content is 16.7 wt%) exhibits a high specific capacitance of 427 F g−1 (at 1 A g−1) and its capacitance can still retain 88% after 1000 cycles.

Low-cost and high energy density asymmetric supercapacitors based on polyaniline nanotubes and MoO3 nanobelts

Asymmetric supercapacitors (ASCs) with high energy density are assembled based on the pseudocapacitance of both electrodes, which use polyaniline (PANI) nanotubes as positive electrodes and MoO3 nanobelts as negative electrodes in a 1 M H2SO4 aqueous electrolyte. The assembled novel PANI//MoO3 ASC device with an extended operating voltage window of 2.0 V, in spite of the use of an aqueous electrolyte, exhibits excellent performance such as a high specific capacitance of 518 F g−1 at a current density of 0.5 A g−1, reaching an energy density as high as 71.9 W h kg−1 at a power density of 254 W kg−1 and good cycling stability.

Formation of Carbon Nanosheets via Simultaneous Activation and Catalytic Carbonization of Macroporous Anion-Exchange Resin for Supercapacitors Application

Two-dimensional mesoporous carbon nanosheets (CNSs) have been prepared via simultaneous activation and catalytic carbonization route using macroporous anion-exchange resin (AER) as carbon precursor and ZnCl2 and FeCl3 as activating agent and catalyst, respectively. The iron catalyst in the skeleton of the AER may lead to carburization to form a sheetlike structure during the carbonization process. The obtained CNSs have a large number of mesopores, a maximum specific surface area of 1764.9 m(2) g(-1), and large pore volume of 1.38 cm(3) g(-1). As an electrode material for supercapacitors application, the CNSs electrode possesses a large specific capacitance of 283 F g(-1) at 0.5 A g(-1) and excellent rate capability (64% retention ratio even at 50 A g(-1)) in 6 mol L(-1) KOH. Furthermore, CNSs symmetric supercapacitor exhibits specific energies of 17.2 W h kg(-1) at a power density of 224 W kg(-1) operated in the voltage range of 0-1.8 V in 0.5 mol L(-1) Na2SO4 aqueous electrolyte, and outstanding cyclability (retains about 96% initial capacitance after 5000 cycles).

A redox mediator doped gel polymer as an electrolyte and separator for a high performance solid state supercapacitor

A stable and effective redox-mediator gel electrolyte has been prepared by doping indigo carmine (IC) into a polyvinyl alcohol sulfuric acid polymer system (PVA–H2SO4), and a high performance solid state supercapacitor is fabricated by utilizing activated carbon as electrodes and the prepared gel polymer (PVA–H2SO4–IC) as an electrolyte and separator. The PVA–H2SO4–IC gel polymer has excellent bending, compressing and stretching mechanical properties. As expected, the ionic conductivity of the gel polymer electrolyte increased by 188% up to 20.27 mS cm−1 while introducing IC as the redox mediator in the PVA–H2SO4 gel electrolyte. Simultaneously, specific capacitance is increased by 112.2% (382 F g−1) and energy density (13.26 W h kg−1) is also increased. Furthermore, the fabricated device shows superior charge–discharge stability. After 3000 cycles, its capacitive retention ratio is still as high as 80.3%. This result may be due to the fact that the IC can act as a plasticizer and redox mediator, and the supercapacitor combines the double-layer characteristic of carbon-based supercapacitors and the faradaic reaction characteristic of batteries energy-storage processes.

One-step preparation of ultrathin nitrogen-doped carbon nanosheets with ultrahigh pore volume for high-performance supercapacitors

A facile one-step activation and nitrogen-doping combination method is developed for preparation of nitrogen-doped graphene-like carbon nanosheets (N-CNSs). The N-CNSs have abundant wrinkled structures and ultrahigh pore volume (3.19 cm3 g−1), and are used as high-performance electrode materials for supercapacitors.

Cotton-based porous activated carbon with a large specific surface area as an electrode material for high-performance supercapacitors

Cotton-based porous activated carbons (CACs) are prepared through a simple chemical activation method using cotton fiber as carbon source and ZnCl2 as activating agent. Powder X-ray diffraction, scanning electron microscopy, and N2 adsorption–desorption tests demonstrate that the carbons activated with different amounts of ZnCl2 have a large number of mesopores, notably, a maximum specific surface area of 2548.6 m2 g−1 and ultrahigh pore volume of 1.54 cm3 g−1 for CAC2 sample are obtained when the cotton/ZnCl2 mass ratio is 1 : 2. As an electrode material for supercapacitors, the CAC2 possesses a high specific capacitance of 239 F g−1 at 0.5 A g−1 and good rate capability (82% capacitance retention even at 8 A g−1) in 2 mol L−1 KOH aqueous electrolyte. Moreover, the as-assembled CAC2//CAC2 symmetric supercapacitor exhibits a high energy density of 13.75 Wh kg−1 at a power density of 225 W kg−1 operated at the voltage range of 0 to 1.8 V in 0.5 mol L−1 Na2SO4 aqueous electrolyte and an excellent cyclability retaining about 93% initial capacitance after 5000 cycles.

Preparation and properties of organic–inorganic composite superabsorbent based on xanthan gum and loess

A new, low-cost, and eco-friendly organic-inorganic composite superabsorbent was successfully synthesized in aqueous solution by polymerization xanthan gum (XG), neutralized acrylic acid (AA) and loess using ammonium persulfate (APS) as initiator and N,N-methylenebisacrylamide (MBA) as crosslinker. Structure and morphological characterizations of the composite superabsorbent were investigated by Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The loess content, pH values, surfactants, salts and temperature which could affect the swelling and water-retention capabilities of the composite superabsorbent were investigated. The composite superabsorbent exhibits excellent water absorbency (610 g/g in distilled water), pH-stability (pH 5-10), and higher swelling capacity in anionic surfactant solution; on the other hand, the composite superabsorbent can be used for removing multivalent metal ions.

A facile and rapid preparation of highly crumpled nitrogen-doped graphene-like nanosheets for high-performance supercapacitors

Highly crumpled nitrogen-doped graphene-like nanosheets (CN-GLSs) with a high specific surface area (1169 m2 g−1) and large pore volume (2.58 cm3 g−1) are prepared from a macroporous resin via simultaneous urea gasification expansion and CaCl2 activation methods. The CN-GLSs are tested as electrodes for supercapacitors and present excellent electrochemical performance.

A novel fabrication of nitrogen-containing carbon nanospheres with high rate capability as electrode materials for supercapacitors

Nitrogen-containing polyaniline-based carbon nanospheres (C-PANI) with diameters of about 200 nm are prepared through a direct carbonization method using polyaniline (PANI) nanospheres as carbon precursors at different temperatures. The PANI nanospheres are synthesized via in situ oxidation polymerization of aniline in the presence of sodium carboxymethyl cellulose as a polymerization template. The C-PANI with 6.69% nitrogen content obtained at 800 °C (C-PANI-800) can achieve a high capacitance of 359 F g−1 at the current density of 1 A g−1 in 6 M aqueous KOH electrolyte, meanwhile maintaining excellent rate capability (81% retention at 20 A g−1). Furthermore, a symmetric supercapacitor fabricated with C-PANI-800 electrodes exhibits an energy density of 17.5 W h kg−1 at a power density of 227 W kg−1 and superior cycle stability (only 4% loss after 5000 cycles), operating in the voltage range of 0–1.8 V in 0.5 mol L−1 Na2SO4 aqueous electrolyte.