Asymmetric Supercapacitor Based on Porous N-doped Carbon Derived from Pomelo Peel and NiO Arrays

A three dimensional (3D) porous framework-like N-doped carbon (PFNC) with a high specific surface area was successfully fabricated through ammonia doping and graphitization based on pomelo peel. The obtained PFNC exhibits an enhanced specific capacitance (260 F g(-1) at 1 A g(-1)) and superior cycling performance (capacitance retention of 84.2% after 10000 cycles at 10 A g(-1)) on account of numerous voids and pores which supply sufficient pathways for ion diffusion during cycling. Furthermore, a fabricated asymmetric PFNC//PFN device based on PFNC and porous flake-like NiO (PFN) arrays achieves a specific capacitance of 88.8 F g(-1) at 0.4 A g(-1) and an energy density of 27.75 Wh kg(-1) at a power density of 300 W kg(-1) and still retains 44 F g(-1) at 10 A g(-1) and 13.75 Wh kg(-1) at power density of 7500 W kg(-1). It is important that the device is able to supply two light-emitting diodes for 25 min, which demonstrates great application potential.

2D quasi-ordered nitrogen-enriched porous carbon nanohybrids for high energy density supercapacitors

Two-dimensional (2D) quasi-ordered nitrogen-enriched porous carbon (QNPC) nanohybrids, with the characteristics of an ultrathin graphite nanosheet framework and thick quasi-ordered nitrogen-doped carbon cladding with a porous texture, have been synthesized via an in situ polymerization assembly method. In the synthesis, the expandable graphite (EG) is enlarged by an intermittent microwave method, and then aniline monomers are intercalated into the interlayers of the expanded EG with the assistance of a vacuum. Subsequently, the intercalated aniline monomers could assemble on the interlayer surface of the expanded EG, accompanied by the in situ polymerization from aniline monomers to polyaniline. Meanwhile, the expanded EG could be exfoliated to graphite nanosheets. By subsequent pyrolysis and activation processes, the QNPC nanohybrids could be prepared. As supercapacitor electrodes, a typical QNPC12-700 sample derived from the precursor containing an EG content of 12%, with a high level of nitrogen doping of 5.22 at%, offers a high specific capacitance of 305.7 F g(-1) (1 A g(-1)), excellent rate-capability and long-term stability. Notably, an extremely high energy density of 95.7 Wh kg(-1) at a power density of 449.7 W kg(-1) in an ionic liquid electrolyte can be achieved. The unique structural features and moderate heteroatom doping of the QNPC nanohybrids combines electrochemical double layer and faradaic capacitance contributions, which make these nanohybrids ideal candidates as electrode materials for high-performance energy storage devices.

GO-induced assembly of gelatin toward stacked layer-like porous carbon for advanced supercapacitors

Layer-like nanocarbons with high surface area and good conductivity are promising materials for supercapacitors due to their good ability for effective charge-transfer and mass-transfer. In this paper, stacked layer-like porous carbon containing RGO (reduced graphene oxides) (LPCG) was constructed via the GO-induced assembly of gelatin followed by carbonization and activation processes. Under suitable conditions, LPCG-based materials with a thickness of about 100 nm and a high specific surface area (up to 1476 m(2) g(-1)) could be obtained. In the materials, the closed combination of RGO and porous carbon can be observed, which is favourable for the development of the synergistic effects of both components. The presence of GO can not only enhance the conductivity of LPCG-based materials, but also is essential for the formation of a thin carbon sheet with a stacked structure. Otherwise, the plate-like, non-stacked carbon with a thickness of about 500 nm could be formed in the absence of RGO. The porous structure along with the presence of RGO allows rapid charge-transfer and easy access and diffusion of electrolyte ions. As a result, the materials exhibited a high discharge specific capacitance (455 F g(-1) at 0.5 A g(-1), 366 F g(-1) at 1 A g(-1)), good rate capability (221 F g(-1) at density 30 A g(-1)) and good cycling stability. In aqueous electrolytes, the energy density could be up to 9.32 W h kg(-1) at a relatively low power density of 500 W kg(-1) with a good cycling stability (>96% over 5000 cycles). It was found that (1) the rational combination of RGO and porous carbon is essential for enhancing the capacitance performance and improving the cycling stability and (2) the high conductivity is favorable for improving the rate performance of the materials. The LPCG-based materials have extensive potential for practical applications in energy storage and conversion devices.

A Self-Quenching-Resistant Carbon-Dot Powder with Tunable Solid-State Fluorescence and Construction of Dual-Fluorescence Morphologies for White Light-Emission

Self-quenching in the aggregation state is overcome, and tunable solid-state photoluminescence of carbon-dot powder is achieved. Furthermore, based on the controllable optical property in organic solvents, a novel concept, i.e., constructing dual-fluorescence morphologies from single luminescent species, is presented to realize white-light emission.

Constructing nitrogen-doped nanoporous carbon/graphene networks as promising electrode materials for supercapacitive energy storage

Nitrogen-doped nanoporous carbon/graphene networks have been constructed and show a larger specific capacitance than that of NPCs and rGO.

Preparation and characterization of a luminescent carbon dots grafted CaSiO3:Eu3+ phosphor for ratiometric fluorescent oxygen sensing

In this work, we present a rapid, selective and highly sensitive sensor for the detection of oxygen based on ratiometric fluorescentcarbon dots (CDs) grafted CaSiO₃:Eu³⁺.

Porous carbon derived from sorghum stalk for symmetric supercapacitors

Sorghum stalk based porous carbons (SSCs) have been synthesized through a simple carbonization method at 800 °C used sorghum stalk as carbon precursor and ZnCl₂ as activating agent.

Is the conductive agent useful in electrodes of graphitized activated carbon?

Partly graphitized AC materials are porous structures with high energy density and power density compared to commercial AC in the absence of conductive agent. Energy and power densities of 48.6 W h kg⁻¹ and 3600 W kg⁻¹ can be maintained at the potential window of 1.5 V.

Nitrogen-Doped Porous Carbons As Electrode Materials for High-Performance Supercapacitor and Dye-Sensitized Solar Cell

Activated N-doped porous carbons (a-NCs) were synthesized by pyrolysis and alkali activation of graphene incorporated melamine formaldehyde resin (MF). The moderate N doping levels, mesopores rich porous texture, and incorporation of graphene enable the applications of a-NCs in surface and conductivity dependent electrode materials for supercapacitor and dye-sensitized solar cell (DSSC). Under optimal activation temperature of 700 °C, the afforded sample, labeled as a-NC700, possesses a specific surface area of 1302 m2 g(-1), a N fraction of 4.5%, and a modest graphitization. When used as a supercapacitor electrode, a-NC700 offers a high specific capacitance of 296 F g(-1) at a current density of 1 A g(-1), an acceptable rate capability, and a high cycling stability in 1 M H2SO4 electrolyte. As a result, a-NC700 supercapacitor delivers energy densities of 5.0-3.5 Wh kg(-1) under power densities of 83-1609 W kg(-1). Moreover, a-NC700 also demonstrates high electrocatalytic activity for I3- reduction. When employed as a counter electrode (CE) of DSSC, a power conversion efficiency (PCE) of 6.9% is achieved, which is comparable to that of the Pt CE based counterpart (7.1%). The excellent capacitive and photovoltaic performances highlight the potential of a-NCs in sustainable energy devices.

Protic-salt-derived nitrogen/sulfur-codoped mesoporous carbon for the oxygen reduction reaction and supercapacitors

Nitrogen/sulfur-co-doped mesoporous carbon (Phen-HS) was obtained through direct carbonization of a single protic salt, that is, 1,10-phenanthrolinium dibisulfate ([Phen][2 HSO4 ]), in the presence of a colloidal silica template without the use of additional acid or metal catalysts for prepolymerization prior to carbonization. Phen-HS was prepared in a relatively high yield (30.0 %) and has a large surface area (1161 m(2)  g(-1) ), large pore volume (2.490 cm(3)  g(-1) ), large mesopores (≈12 nm), narrow pore-size distribution (7-16 nm), and high nitrogen (7.5 at %) and sulfur (1.3 at %) contents. The surface area/pore-size distribution is much higher/narrower than that of most reported carbon materials obtained from traditional precursors by using the same template. Phen-HS was directly used as an electrocatalyst for the oxygen reduction reaction (ORR) and as an electrode material for supercapacitors. As an efficient metal-free catalyst, Phen-HS exhibited good electrocatalytic activity toward the ORR in a 0.1 M KOH aqueous solution, which is comparable to the activity of a commercial Pt/C catalyst. Electrochemical measurements for Phen-HS used in a double-layer capacitor showed high specific capacitances of 160 and 140 F g(-1) in 1 M H2 SO4 and 6 M KOH, respectively, with good rate capabilities and high cycling stabilities.

Hierarchical porous carbon materials with high capacitance derived from Schiff-base networks

A type of hierarchical porous carbon material was prepared using a Schiff-base network as the precursor and ZnCl2 as the activation agent, and their electrochemical performances were investigated in acid and alkaline aqueous solutions, respectively. The as-prepared materials have high surface areas, appropriate distributions of hierarchical pore sizes, and various forms of nitrogen/oxygen derivatives. These structural advantages guarantee the outstanding performances of such carbon materials as electrodes for supercapacitors, which include high specific capacitances, fast current responses, and high cycling stabilities.

Hierarchical microporous/mesoporous carbon nanosheets for high-performance supercapacitors

A straightforward one-pot approach for the synthesis of highly porous carbon nanosheets with an excellent performance as supercapacitor electrodes is presented. The procedure is based on the carbonization of an organic salt (i.e., sodium gluconate) at a temperature in the range of 700-900 °C. The carbon nanosheets have a large aspect ratio (length/thickness ≈ 10(2)-10(3)), a thickness within the range of 40-200 nm, high BET surface areas (SBET) of up to 1390 m(2) g(-1), and a porosity with a hierarchical organization in the micropore-mesopore range. Importantly, via an additional activation step, the textural properties can be substantially enhanced (SBET up to 1890 m(2) g(-1)). Both the nanosheet morphology (short diffusional paths) and the hierarchical microporous/mesoporous pore structure allow the rapid transport of ions throughout the carbonaceous matrix, leading to excellent electrochemical performance. Thus, the hierarchical nanosheets exhibit specific capacitances of up to 140 F g(-1) at an ultrahigh discharge current of 150 A g(-1) in 1 M H2SO4 and 100 F g(-1) at 120 A g(-1) in 1 M TEABF4/AN. The maximum specific power recorded in an aqueous electrolyte is ∼ 20-30 kW kg(-1) and ∼ 90-110 kW kg(-1) in an organic electrolyte. These promising power characteristics are accompanied by excellent cycling stability.

Nitrogen-doped graphene aerogels as efficient supercapacitor electrodes and gas adsorbents

Nitrogen-doped graphene has been demonstrated to be an excellent multifunctional material due to its intriguing features such as outstanding electrocatalytic activity, high electrical conductivity, and good chemical stability as well as wettability. However, synthesizing the nitrogen-doped graphene with a high nitrogen content and large specific surface area is still a challenge. In this study, we prepared a nitrogen-doped graphene aerogel (NGA) with high porosity by means of a simple hydrothermal reaction, in which graphene oxide and ammonia are adopted as carbon and nitrogen source, respectively. The microstructure, morphology, porous properties, and chemical composition of NGA were well-disclosed by a variety of characterization methods, such as scanning electron microscopy, nitrogen adsorption-desorption measurements, X-ray photoelectron spectroscopy, and Raman spectroscopy. The as-made NGA displays a large Brunauer-Emmett-Teller specific surface area (830 m(2) g(-1)), high nitrogen content (8.4 atom %), and excellent electrical conductivity and wettability. On the basis of these features, the as-made NGA shows superior capacitive behavior (223 F g(-1) at 0.2 A g(-1)) and long-term cycling performance in 1.0 mol L(-1) H2SO4 electrolyte. Furthermore, the NGA also possesses a high carbon dioxide uptake capacity at 1.0 bar and 273 K (11.3 wt %).

Electrochemical energy storage and adsorptive dye removal of Platanus fruit-derived porous carbon

Activated Platanus fruit carbon (a-PFC) was synthesized by pyrolytic carbonization and alkali activation treatment of an easily available biomass, Platanus fruit (PF).

White clover based nitrogen-doped porous carbon for a high energy density supercapacitor electrode

We employed the biomaterial white clover as a carbon precursor and ZnCl₂ as an activating agent to prepare white clover carbons (WCCs).

Polyacrylamide-derived carbon materials: outstanding enhancement of supercapacitor capacitance simply by introducing redox additive of p-aminobenzenesulfonate into KOH electrolyte

A simple but efficient redox additive of sodium p-aminobenzenesulfonate has been incorporated into KOH electrolyte, which can largely elevate the capacitances of carbon-based supercapacitors.

Polybenzoxazine-based nitrogen-containing porous carbons for high-performance supercapacitor electrodes and carbon dioxide capture

Nitrogen-containing porous carbons were synthesized from a novel polybenzoxazine for high-performance supercapacitor electrode and carbon dioxide capture.

Needle-like MnO2/activated carbon nanocomposites derived from human hair as versatile electrode materials for supercapacitors

Efficient needle-like MnO₂/activated carbon nanocomposites have been prepared and demonstrated as versatile electrode materials for supercapacitors.

Fluorescent carbon quantum dots, capacitance and catalysis active porous carbon microspheres from beer

Fluorescent nitrogen containing carbon quantum dots (NCQDs) and porous carbon microspheres (PCMs) were simultaneously synthesized by a facile hydrothermal method using beer as precursor.

Facile synthesis of nitrogen-doped unzipped carbon nanotubes and their electrochemical properties

N-UCNTs with a high nitrogen level, large surface areas and good crystallinity are synthesized by pyrolysis of an O-UCNTs/melamine composite.

A honeycomb-like porous carbon derived from pomelo peel for use in high-performance supercapacitors

A cost-effective approach to obtain electrode materials with excellent electrochemical performance is critical to the development of supercapacitors (SCs). Here we report the preparation of a three-dimensional (3D) honeycomb-like porous carbon (HLPC) by the simple carbonization of pomelo peel followed by KOH activation. Structural characterization indicates that the as-prepared HLPC with a high specific surface area (SSA) up to 2725 m(2) g(-1) is made up of interconnected microporous carbon walls. Chemical analysis shows that the HLPC is doped with nitrogen and also has oxygen-containing groups. Electrochemical measurements show that the HLPC not only exhibits a high specific capacitance of 342 F g(-1) and 171 F cm(-3) at 0.2 A g(-1) but also shows considerable rate capability with a retention of 62% at 20 A g(-1) as well as good cycling performance with 98% retention over 1000 cycles at 10 A g(-1) in 6 M KOH. Furthermore, an as-fabricated HLPC-based symmetric SC device delivers a maximum energy density of ∼9.4 Wh kg(-1) in the KOH electrolyte. Moreover, the outstanding cycling stability (only 2% capacitance decay over 1000 cycles at 5 A g(-1)) of the SC device makes it promising for use in a high-performance electrochemical energy system.

Nitrogen-doped aligned carbon nanotube/graphene sandwiches: facile catalytic growth on bifunctional natural catalysts and their applications as scaffolds for high-rate lithium-sulfur batteries

Nitrogen-doped aligned CNT/graphene sandwiches are rationally designed and in-situ fabricated by a facile catalytic growth on bifunctional natural catalysts that exhibit high-rate performances as scaffolds for lithium-sulfur batteries, with a high initial capacity of 1152 mA h g(-1) at 1.0 C. A remarkable capacity of 770 mA h g(-1) can be achieved at 5.0 C. Such a design strategy for materials opens up new perspectives to novel advanced functional composites, especially interface-modified hierarchical nanocarbons for broad applications.