Hierarchical porous carbon derived from coal-based carbon foam for high-performance supercapacitors

Hierarchical porous carbon (HPC) from bituminous coal was designed and synthesized through pyrolysis foaming and KOH activation. The obtained HPC (NCF-KOH) were characterized by a high specific surface area (S_BET) of 3472.41 m²/g, appropriate mesopores with V_mes/V_total of 57%, and a proper amount of surface oxygen content (10.03%). This NCF-KOH exhibited a high specific capacitance of 487 F/g at 1.0 A/g and a rate capability of 400 F/g at 50 A/g based on the three-electrode configuration. As an electrode for a symmetric capacitor, a specific capacitance of 299 F/g at 0.5 A/g was exhibited, and the specific capacitance retained 96% of the initial capacity at 5 A/g after 10,000 cycles. Furthermore, under the power density of 249.6 W/kg in 6 mol/L KOH, a high energy density of 10.34 Wh/kg was obtained. The excellent charge storage capability benefited from its interconnected hierarchical pore structure with high accessible surface area and the suitable amount of oxygen-containing functional groups. Thus, an effective strategy to synthesize HPC for high-performance supercapacitors serves as a promising way of converting coal into advanced carbon materials.     

Mesopore-dominant porous carbon derived from bio-tars as an electrode material for high-performance supercapacitors

For the first time, toxic bio-tars collected from the gasification of pine sawdust are used as the precursor for activated carbons. Various types of activation agents including KOH, K₂CO₃, H₃PO₄ and ZnCl₂ were screened for obtaining superior activated carbons. When KOH was used as an activation agent, the obtained activated carbons exhibited high specific surface area and large mesopore volume. The activated carbons were further employed to be the electrode material of supercapacitors, and its specific capacitance reached up to 260 F g^?1 at 0.25 A g^?1 current density. Also, it showed an excellent rate performance from preserving a relatively high specific capacitance of 151 F g^?1 at 50 A g^?1. The assembled device also exhibited the good electrochemical stability with the capacity retention of 90% after 5000 cycles. Furthermore, the maximum energy density of the activated carbons in organic electrolyte reached 17.8 Wh kg^?1.     

Recent advances in carbon nanostructures prepared from carbon dioxide for high-performance supercapacitors

The burgeoning global economy during the past decades gives rise to the continuous increase in fossil fuels consumption and rapid growth of CO₂ emission,which demands an urgent exploration into green and sustainable devices for energy storage and power management.Supercapacitors based on activated carbon electrodes are promising systems for highly efficient energy harvesting and power supply,but their promotion is hindered by the moderate energy density compared with batteries.Therefore,scalable conversion of CO₂ into novel carbon nanostructures offers a powerful alternative to tackle both issues:mitigating the greenhouse effect caused by redundant atmospheric CO₂ and providing carbon materials with enhanced electrochemical performances.In this tutorial review,the techniques,opportunities and barriers in the design and fabrication of advanced carbon materials using CO₂ as feedstock as well as their impact on the energy-storage performances of supercapacitors are critically examined.In particular,the chemical aspects of various Cv2 conversion reactions are highlighted to establish a detailed understanding for the science and technology involved in the microstructural evolution,surface engineering and porosity control of CO₂-converted carbon nanostructures.Finally,the prospects and challenges associated with the industrialization of CO₂ conversion and their practical application in supercapacitors are also discussed.     

Lignin-derived hierarchical porous carbon for high-performance supercapacitors

Journal of Solid State Electrochemistry - Lignin as the second most abundant natural polymer was applied to prepare a hierarchical porous carbon (HPC) for supercapacitors (SCs). Direct activation...     

Reed straw derived active carbon/graphene hybrids as sustainable high-performance electrodes for advanced supercapacitors

Reed straw-derived active carbon@graphene (AC@GR) hybrids were prepared by one-step carbonization/activation process using a mixture of reed straw and graphene oxide (GO) as raw materials and ZnCl₂ as activation agent. The as-prepared hybrids exhibit high specific surface area in a range of 1971–2497 m² g^?1, abundant porosity, as well as excellent energy storage capability. The symmetric C//C supercapacitor using the hybrid obtained at 700 °C as electrodes demonstrates superior cycling durability, ca. 90 % retention after 6000 cycles at 2 A g^?1, and a high energy density of 6.12 Wh kg^?1 at a power density of up to 4660 W kg^?1 in 6 M KOH aqueous electrolyte. The excellent capacitive performance is attributed to the synergistic effect of AC and GR.     

Thiourea aldehyde resin-based carbon/graphene composites for high-performance supercapacitors

Thiourea aldehyde resin-based heteroatom doping carbon and graphene composites (RHDC/GN) were prepared by an in situ polymerization and carbonization. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images showed that thiourea aldehyde resin deposited on lamellar GO flakes during the polymerization and RHDC/GN composites had a hierarchical structure. The specific capacitance of the RHDC/GN composites was high up to 355 F g^?1, much higher than that of the pure thiourea aldehyde resin-based heteroatom doping carbon (RHDC) with specific capacitance of 135 F g^?1 at a current density of 1.0 A g^?1 in 6-M KOH electrolyte. And the hetroatoms in RHDC/GN composites increase the specific capacitance, and GN enhances the conductivity of the electrodes which is beneficial to improving electrochemical cycling stability of the electrode significantly. The specific capacitance retains 90.97% after 5000 charge-discharge processes at 10 A g^?1, which provides potential as supercapacitors.     

Pomegranate rind-derived activated carbon as electrode material for high-performance supercapacitors

In this paper, activated carbon materials were synthesized from pomegranate rind through carbonization and alkaline activation processes. The effects of pyrolytic temperature on the textual properties and electrochemical performance were investigated. The surface area of the activated carbon can reach at least 2200 m² g^?1 at different pyrolytic temperatures. It was found that, at the range of 600–900 °C, decreasing the carbonization temperature leads to the increase of t-plot micropore area, t-plot micropore volume, and capacitance. Further decreasing the carbonization temperature to 500 °C also leads to the increase of t-plot micropore area and t-plot micropore volume, but the capacitance is slightly poorer. The activated carbon carbonized at 600 °C and activated at 800 °C possesses very high specific area (2931 m² g^?1) and exhibits very high capacitance (～268 F g^?1 at 0.1 A g^?1 and ～242 F g^?1 at 1 A g^?1). There is no capacitance fading after 2000th cycle.     

N,P dual-doped hollow carbon spheres for high-performance supercapacitors

Journal of Solid State Electrochemistry - A series of nitrogen (N) and phosphorus (P) dual-doped hollow carbon spheres (NPHCSs) with different contents of N and P were synthesized by Stöber...     

Activated carbon derived from tree bark biomass with promising material properties for supercapacitors

Journal of Solid State Electrochemistry - Activated carbon from tree bark (ACB) has been synthesized by a facile and environmentally friendly activation and carbonization process at different...     

Resorcinol-formaldehyde carbon spheres/polyaniline composite with excellent electrochemical performance for supercapacitors

Well-dispersed resorcinol-formaldehyde-based carbon spheres (RFCs) have been prepared by the polycondensation of resorcinol and formaldehyde with ammonia as catalyst and subsequent carbonization of the obtained polymer. In situ polymerization of the aniline occurred in the suspension of the RFC, and RFC was surrounded by the polyaniline (PANI) wires. The PANI and RFC hybrid network (PRFC) formed gradually. In a three-electrode mode, the specific capacitance (C _sp) of PRFC reaches 315 F g^?1 at a current density of 1 A g^?1 in 2 M H₂SO₄, much higher than that of pure PANI (225 F g^?1) and RFC (121.7 F g^?1). Furthermore, the C _sp of PRFC retains 80.0 % after 1000 charge-discharge processes at a current density of 5 Ag^?1. The enhanced electrochemical performance of the PRFC came from its homogeneous three-dimensional hierarchical network structure, good electric conductivity of the PANI around the RFC, and the synergistic effect between the RFC and PANI.     

A renewable bamboo carbon/polyaniline composite for a high-performance supercapacitor electrode material

A high-performance conducting polymer-activated carbon composite electrode material was prepared by potentiostatic deposition of aniline on a hierarchically porous carbon, which was carbonized from the natural bamboo. The obtained composite combined the contribution of the unique properties of the activated carbon and pseudocapacitance of the deposited polyaniline layer. This active material possessed excellent rate capability and good cycle performance, over 92% of the original capacitance is retained after 1,000 cycles. The energy density of the composite can reach 47.5 W h kg⁻¹ calculated only by active mass. It can be a good candidate for high-performance supercapacitor.     

A facile synthesis of hierarchical porous carbon derived from renewable lignin for high-performance supercapacitor

In this work, we proposed a facile one-pot pyrolysis method to conveniently manufacture lignin-derived carbon materials with graded porous construction for use in supercapacitors. The renewable lignin was selected as precursor, while the potassium citrate was used as a pore-forming agent. The properties of the prepared lignin-derived carbon (LAC) and the performance for supercapacitor application were thoroughly evaluated. The LAC at optimal preparation conditions shows a layered porous structure with a large specific surface area of 3174 cm² g⁻¹ and pore volume of 2.796 cm³ g⁻¹, where the specific capacitance reach to 241 F g⁻¹ at 1 A g⁻¹ scan rate in 6 M KOH electrolyte solution. At the same time, the specific capacitance remains at 220 F g⁻¹ even at an excessive scan velocity of 20 A g⁻¹, while the capacitance retention is still close to 91.3%. The capacitance retention rate is stable above 95% after 10,000 charge/discharge cycles, which shows the desired long-time stability. All these results demonstrate the outstanding properties of the new prepared LAC material and the considerable application potential in the field of electrical energy storage.     

Graphene oxide doped polyaniline for supercapacitors

A novel high-performance electrode material based on fibrillar polyaniline (PANI) doped with graphene oxide sheets was synthesized via in situ polymerization of monomer in the presence of graphene oxide, with a high conductivity of 10 S cm^?1 at 22 °C for the obtained nanocomposite with a mass ratio of aniline/graphite oxide, 100:1. Its high specific capacitance of 531 F/g was obtained in the potential range from 0 to 0.45 V at 200 mA/g by charge–discharge analysis compared to 216 F/g of individual PANI. The doping and the ratio of graphene oxide have a pronounced effect on the electrochemical capacitance performance of the nanocomposites.     

Phenylenediamine-formaldehyde chemistry derived N-doped hollow carbon spheres for high-energy-density supercapacitors

Porous carbon spheres represent an ideal family of electrode materials forsupercapacitors because of the high surface area,ideal conductivity,negligible aggregation,and ability to achieve space efficient packing.However,the development of new synthetic methods towards porous carbon spheres still remains a great challenge.Herein,N-doped hollow carbon spheres with an ultrahigh surface area of2044 m²/g have been designed based on the phenylenediamine-formaldehyde chemistry.When applied in symmetric supercapacitors with ionic electrolyte(EMIBF_4),the obtained N-doped hollow carbon spheres demonstrate a high capacitance of 234 F/g,affording an ultrahigh energy density of 114.8 Wh/kg.Excellent cycling stability has also been achieved.The impressive capacitive performances make the phenylenediamine-formaldehyde resin derived N-doped carbon a promising candidate electrode material for supercapacitors.     

Promising activated carbons derived from cabbage leaves and their application in high-performance supercapacitors electrodes

In this paper, cabbage leaves (CLs) were used to synthesize porous activated carbon by the carbonization and activation processes. The material for CLs were carbonized at 600 °C and activated at 800 °C with the KOH/C-600 mass ratio 4 (denoted as AC-800) show typical amorphous character and display porous structures with high specific surface areas 3102 m²/g via XRD and BET measurements. As the electro-active material, AC-800 electrode exhibit ideal capacitive behaviors in aqueous electrolytes and the maximal specific capacitance is as high as 336 F/g at the current density of 1 A/g. Furthermore, AC-800 electrode shows excellent electrochemical cycle stability with ～95 % initial capacitance being retained after 2000 cycles. The desirable capacitive performances enable the CLs to act as a new biomass source of carbonaceous materials for high-performance supercapacitors and low-cost electrical energy storage devices.     

Porous carbon synthesized by direct carbonization of potassium biphthalate for high-performance supercapacitors

Porous carbons have been synthesized by a direct carbonization of potassium biphthalate without an activation process. The experimental results demonstrate that the carbonization temperature plays a crucial role in determining the surface area and pore structure as well as the correlative capacitive performance. The carbon-700/800/900 samples display surface areas of 672, 1,023, and 1,380 m² g^?1 and total pore volumes of 0.38, 0.56, and 0.78 cm³ g^?1, respectively. The specific capacitances of the carbon-700/800/900 samples are 300.4, 272.3, and 243.4 F g^?1, respectively, at a current density of 0.5 A g^?1. More importantly, the carbon-900 sample possesses the highest capacitance retention (~98.4 %) even undergoing charge–discharge 10,000 times. The potassium biphthalate used as a carbon source is inexpensive and commercially available, making it promising for the large-scale production of porous carbons as an excellent electrode material for supercapacitors.     

Biomass-derived porous carbon electrode modified with nanostructured nickel-cobalt hydroxide for high-performance supercapacitors

Journal of Solid State Electrochemistry - Apple-derived porous carbon (denoted as APC) is successfully prepared and analyzed as a potential carbon material by hydrothermal carbonization and...     

Interlaced polyaniline/carbon nanotube nanocomposite co-electrodeposited on TiO<Subscript>2</Subscript> nanotubes/Ti for high-performance supercapacitors

A series of PANI-CNTs/TiO₂ nanotubes/Ti electrodes were fabricated via pulse current co-electrodeposition of polyaniline and functionalized carbon nanotubes onto TiO₂ nanotubes/Ti electrodes. FT-IR spectrometry, X-ray photoelectron spectroscopy, and scanning electron microscopy were applied in order to characterize the modified TiO₂ nanotubes/Ti electrodes. The morphology studies showed that the PANI-CNTs/TiO₂ nanotubes/Ti nanocomposite electrode has many interlaced PANI-CNTs nanorods on the surface of TiO₂ nanotubes. The electrochemical measurements of the modified electrodes confirmed that the CNTs in the composite can significantly improve the capacitive behavior as well which have been compared with that of PANI/TiO₂ nanotubes/Ti electrodes. The modified electrode exhibited much higher specific capacitance (190 mF cm^?2 with 90% retention after 1000 cycles) compared to the PANI/TiO₂ nanotubes/Ti (70 mF cm^?2 with 77% retention after 1000 cycles) at a current density of 0.85 mA cm^?2, indicating its great potential for supercapacitor applications.

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Graphical abstract Interlaced polyaniline/carbon nanotube nanocomposite electrodeposited on TiO₂ nanotubes/Ti