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In this study, a facile pyrolysis process is utilized to convert a mantis shrimp shell into a 3D bicontinuous porous, highly wrinkled, nitrogen-doped, graphene-like ultrathin carbon sheet (3D BWGC). The 3D BWGC achieves a high surface area of 2300 m2 g−1 and a pore volume of up to 1.63 cm3 g−1. The specific capacitance of the 3D BWGC in 0.5 M H2SO4 electrolyte is 370.9 F g−1 at a current density of 1 A g−1 and an operating voltage window of 1.1 V. By introducing Fe2+, the operating voltage window of 3D BWGC symmetric supercapacitors can reach 1.8 V in a neutral electrolyte, and a specific capacitance of 317.2 F g−1 can be obtained at a current density of 0.5 A g−1. Remarkably, the fabricated symmetric supercapacitors using 2 M MgSO4 + 0.05 M FeSO4 electrolyte demonstrated an energy density as high as 17.7 W h kg−1 at a power density of 180 W kg−1. The assembled supercapacitors exhibit good cycling performance, maintaining an initial capacitance of 87.2% over 30 000 cycles. These excellent performances indicate the promising prospects of 3D BWGC in high-performance electrochemical energy storage. [ABSTRACT FROM AUTHOR]

Direct carbonization of nitrogen-containing precursors combined with activation is an effective way to prepare nitrogen-doped hierarchical porous carbon. The most common activation agents being used such as KOH and NaOH may cause serious corrosion to the manufacturing equipment. To resolve this problem, a facile approach has been developed to prepare phenolic resin-derived nitrogen-doped hierarchical porous carbon using sodium acetate as the activation agent and hexamethylenetetramine as the nitrogen source. Acting as an in situ activation agent, sodium acetate is less corrosive. The results show that the sample obtained at 900°C (PHS-900) reaches a maximum specific surface area (SBET) of 1591 m2 g−1. Benefiting from the optimum balance between high nitrogen content (5.41 at.%) and relatively large surface area (827 m2 g−1), the optimal sample PHS-700 exhibits a high specific capacitance of 352 F g−1 when it is used as an electrode in 7 M KOH aqueous electrolyte with a three-electrode system. Furthermore, it also shows excellent long-term stability in a two-electrode cell (95.3% retention after 10 000 cycles). The good electrochemical performance of the samples and the low corrosion, template-free preparation make it a promising strategy to fabricate nitrogen-doped hierarchical porous carbon for supercapacitor electrode materials. [ABSTRACT FROM AUTHOR]

A series of nitrogen-doped (N-doped) polymeric resin-derived porous carbons (NPCs) have been fabricated by a direct carbonization of the mixture of polymeric resin and potassium acetate. The polymeric resin serves as carbon and nitrogen precursor and potassium acetate as activation agent. The prepared carbons have a high specific surface area of 1946 m 2  g −1 and high N content of approximately 6.37 at%. The NPC-700 sample exhibits a highest specific capacitance of 312 F g −1 at 0.5 A g −1 in a three-electrode system in 7 M KOH. When tested with a two-electrode system, the optimal sample NPC-800 shows a good rate performance (capacitance retention of 73% in the range of 0.05 A g −1 to 20 A g −1 ) and high cycling stability (96.5% retention after 5000 cycles at 2 A g −1 ). The easy preparation and superior electrochemical performances render the NPCs a promising alternative electrode material for supercapacitor. [ABSTRACT FROM AUTHOR]

Nitrogen-containing carbon sphere with hierarchical porous structure is obtained through a facile thermostabilization and carbonization method of biomass-derivative sodium lignosulfonate. The synthesis route we proposed is cost-effective and environment-friendly without additional nitrogen precursor, activation or templating agent. The as-prepared carbon spheres exhibit high specific surface area of 1255–1939 m 2  g −1 and moderate surface nitrogen content of 1.14–1.66 at.%. When assembling into supercapacitors with 7 M KOH aqueous solution as electrolyte, the carbon sphere shows superior gravimetric specific capacitance up to 276 F g −1  at 0.1 A g −1 , high gravimetric energy density of 7.8 Wh kg −1 and power density of 6.2 kW kg −1 , together with unprecedented cycling stability (99.5% capacitance retention after 10000 cycles). Notably, in 1 M SBPBF 4 /PC organic electrolyte, the carbon sphere based supercapacitor presents impressive gravimetric energy density of 34.3 Wh kg −1 and power density of 9.4 kW kg −1 . These outstanding electrochemical performances suggest that the as-prepared porous carbon spheres should be a promising candidate for the field of energy storage. [ABSTRACT FROM AUTHOR]

Nitrogen-doped hierarchical porous carbon materials were simply prepared from phenolic formaldehyde resin using sodium citrate as activation agent and hexamethylenetetramine as nitrogen source. The hierarchical porous structure of the obtained carbon samples is helpful for ion transport and greatly promote the capacitance properties of the carbon materials. The physical and chemical properties tests show that the as-prepared materials have characteristics of amorphous carbons. The low-temperature N2 sorption experiment shows that the maximum BET specific area of the as-prepared samples can be up to 1256 m2 g−1, with an ideal hierarchical porous structure comprised of a large number of micropores and a certain amount of mesopores and macropores. X-ray photoelectron spectroscopy demonstrates the NHPCs have high doping (1.56–6.19 wt%) and oxygen content (6.43–11.88 at.%). Benefitting from both the high specific surface area and distinct hierarchical porous structure, the obtained samples exhibit excellent electrochemical performances when used as electrode materials. The optimal sample exhibits a high specific capacitance (CSP) of 261 F g−1 at a 0.05 A g−1, with a good rate capability of 71% (185 F g−1 at 20 A g−1). The carbon material also shows an excellent long cycle stability (98% capacitance retention after 5000 cycles). All results indicate that the work sheds light on the technological innovation in carbon materials for energy storage. [ABSTRACT FROM AUTHOR]

We developed a one-pot strategy to fabricate activated carbons by using water soluble phenol-formaldehyde resin as precursor and Na 2 CO 3 as activating agent. The prepared carbon materials have a typical hierarchical pore texture and a large specific surface area (SSA) of 1357 m 2 g −1 . When used as electrode materials for supercapacitors, the material shows a high specific capacitance of 226 F g −1 at 0.05 A g −1, good rate capability of 62.4% in the range of 0.05–20 A g −1 and outstanding cycling stability (only 2.5% loss in specific capacitance after 5000 cycles). These results suggest a low-cost and environmentally friendly design of electrode materials for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Interconnected hierarchical porous carbon was successfully prepared by direct carbonization of industrial waste sodium lignosulfonate without additional templating and activation agents. The as-prepared carbon sample shows a moderate specific surface area of 903 m2 g−1 and high contents of 8.11 at% oxygen and 1.76 at% nitrogen, which could improve the electrolyte-affinitive surface area in an aqueous electrolyte. When used as electrode materials for symmetric supercapacitors in 7 M KOH electrolytes, the as-synthesized carbon sample exhibits a significantly high gravimetric capacitance of 247 F g−1, a volumetric capacitance of 240 F cm−3, and an areal capacitance of 27.4 μF cm−2 at a current density of 0.05 A g−1. Moreover, a superior energy density of 8.4 W h L−1 (at 13.9 W L−1) and a power density of 5573.1 W L−1 (at 3.5 W h L−1), as well as a remarkable cycling stability after 20 000 cycles at two different current densities were achieved for the assembled supercapacitors. [ABSTRACT FROM AUTHOR]

A novel strategy for the synthesis of hierarchical porous carbons (HPCs) from resol by potassium acetate activation for advanced supercapacitor electrodes was reported. The resultant HPCs with a high specific surface area up to 1201 m 2 g −1 as a supercapacitor electrode exhibits a high specific capacitance of 226 F g −1 at 0.05 A g −1 . Besides, the electrode shows high rate capability with 62.4% retention from 0.05 to 20 A g −1 . Moreover, it demonstrates good cyclic stability, showing a high capacitance retention of 97.1% over 5000 charge-discharge cycles at 2.0 A g −1 . The facile, efficient and template-free synthesis strategy for novel 3D-HPCs may promote commercial application of HPCs in the fields of supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: Porous carbons are derived by carbonizing coal tar pitch with one dimension non-silica template (needle-like nano-sized MgO). The samples are characterized by nitrogen adsorption at 77K and XRD analysis. The electrochemical performances for supercapacitor are evaluated in a 6M KOH aqueous solution. The results show that the as-prepared porous carbons possess abundant mesopores of 3.7–6.5nm. With air stabilization process, the samples possess more micropores, contributing nearly 50% of surface areas. The porous carbon with large template content through air stabilization possess a high surface area of 864m2 g−1. For supercapacitors electrode material, the porous carbon shows a high capacity and excellent power performance, retaining 100Fg−1 even at a current density of 30Ag−1. [Copyright &y& Elsevier]

Abstract: Mesoporous carbons are prepared from a mixture of the soluble starch with needle-like nano-sized Mg(OH)2 particles. The samples structures are characterized by TEM, nitrogen adsorption at 77K and XRD. The electrochemical performance for electrochemical capacitors is evaluated in a 6M KOH aqueous solution. The resultant carbons show a disordered pore structure with interweaving straight nano-tunnels that resembled the shape of the template, and possess a high surface area more than 1000m2 g−1 and a large pore volume. The special one dimensional morphology of templates cause a graphitization effect on the carbon in partial region, different from catalytic graphitization mechanism of transition metal particles. Due to those characteristics, the samples exhibit good electrochemical performances used for electrochemical capacitors electrode, especially excellent power capability. The sample carbonized at 950°C for 6h retain a capacitance of 126Fg−1 even at a high current density of 40Ag−1. [Copyright &y& Elsevier]

Abstract: Porous carbon was prepared from deoiled asphalt by conventional NaOH activation process and by the combination of nano-sized MgO template method and NaOH activation process. The electrochemical properties used as supercapacitors electrode material were evaluated in 7M KOH aqueous solution. Porous carbon sample obtained by NaOH activation possessed more micropores and higher specific surface area, resulting in a higher specific capacitance of 235Fg−1 at low charge–discharge current of 50mAg−1. For the combination method, the resultant carbons possessed higher capacitance and good capacitance maintaining at high current, with a capacitance of nearly twice as that of the former at current density of 10Ag−1, due to their abundant mesopores. [Copyright &y& Elsevier]

Abstract: This paper introduces a silicon three-dimensional (3D) micro supercapacitor, featured by using self-supporting nano porous composite materials and interdigital electrodes with high-aspect-ratio. A way to prepare self-supporting materials has been developed, and composites that contain an activated carbon as the active component have been studied and designed to meet the requirements for adequate specific capacitance, good conductivity and strong structure. By combining the designed composite with microfabrication techniques, a micro supercapacitor with high-aspect-ratio interdigital electrodes has been achieved. Electrochemical characterization results of the prototype with NaNO3 electrolyte demonstrate that the 3D supercapacitor exhibits an outstanding overall performance. A large capacitance of 90.7mFcm−2 and a fast power of 51.5mWcm−2 are calculated. Robust stability and high charge/discharge efficiency are also observed. Moreover, this study provides a scalable device built by compatible fabrication method, which is applicable to the integration of high-performance supercapacitors on chip. [Copyright &y& Elsevier]

Graphene is considered as a promising electrode material for supercapacitors due to its large specific surface area, excellent electrical conductivity and so on. In this paper, few-layer graphene is prepared by self-propagating combustion reaction between CO and metal magnesium, using powder MgO as deposition template. Graphene with a high specific surface area of up to 928 m2 g−1 replicates the morphological feature of powder MgO. Raman spectroscopy analysis demonstrates that the graphene layer decreases when the dosage of MgO template is increased. The specific capacitance of as-prepared sample exhibits the highest specific capacitance of 222 F g−1 at the current density of 1 A g−1 in EMI [TFSI] electrolyte. The sample demonstrates a "double high" performance with high specific energy density and high specific power density. A high energy density of 76.3 Wh kg−1 can be achieved at a specific power density of 1.75 kW kg−1, and it can still remain 48.6 Wh kg−1 when the specific power density reaches a high level of 35 kW kg−1. • Self-propagating combustion reaction synthesis graphene. • Synthesis graphene from CO and Mg. • Synthesized graphene has good structural properties. • Excellent capacitive performances in the electrolyte of EMI [TFSI]. [ABSTRACT FROM AUTHOR]

Abstract: This paper demonstrates an asymmetric micro supercapacitor with superior overall performance that combines the advantages of both MnO2 positive electrode and carbon negative electrode for energy storage on a chip. Nano-structured MnO2 with rough surface is synthesized as active material for micro electrode. A self-supporting composite containing MnO2 and another containing nanoporous activated carbon (AC) are separated in an interdigital structure by using micro-electro-mechanical systems (MEMS) fabrication technologies. Measurements of the prototype show that the asymmetric micro supercapacitor has well-performed capacitive behavior, and its working voltage range is extended from 1 V to 1.5 V in aqueous electrolyte due to the MnO2–AC configuration. Calculations prove that it stores much higher energy densities than symmetric ones using either MnO2 or AC. Moreover, this work provides an attractive approach to achieve various asymmetric micro energy storage systems on chips. [Copyright &y& Elsevier]

Abstract: A series of polyaniline/carbon nanotube array (PANI/CNTA) composite electrodes are prepared by electrodeposition of PANI onto CNTA electrodes by 100–500 cyclic voltammetry (CV) cycles, with the aim to investigate the influence of microstructure on the capacitive performance of PANI/CNTA composites. The morphology of PANI/CNTA composites varies remarkably with the CV cycles of electrodeposition. The optimum condition is obtained for the PANI/CNTA composite prepared by 100 CV cycles, corresponding to the highest specific capacitance, best rate performance, and longest cycle life, which are much better than that of activated carbon fiber cloth, the PANI electrodeposited on stainless steel substrate, and CNTA electrode. The forming process of the microstructure and its influence on the capacitive performance of PANI/CNTA composites are presented in this paper. [Copyright &y& Elsevier]