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We report the optimized electrochemical performance of a hybrid supercapacitor constructed with cokes‐derived activated carbon (CAC) and Li4Ti5O12/carbon nanotube (LTO/CNT), which has improved capacitance and rate capability. The improved capacitance of the CAC is attributed to additional shallow intercalation due to the remaining graphitic structure with ion adsorption via optimized surface area and pore structure. The graphitic structure is partially maintained via adjusted KOH activation conditions. The improved rate capability of LTO/CNT is affected by the increase in electronic conductivity, which entails the formation of an electron pathway via a 3D CNT network, whereas nanosized LTO arrangements are embedded in the CNT structure. The maximum energy and power densities of the hybrid supercapacitor are 69.1 Wh kg−1 and 16.5 W kg−1, respectively, whereas the cycle‐life performance is 88 % after 8000 cycles. This hybrid supercapacitor can allow for the expansion of the application of supercapacitors. [ABSTRACT FROM AUTHOR]

In this study, activated carbon was prepared from lignocellulosic biomass and its electrochemical properties were analyzed and compared. The highest total specific net energy efficiency was 1.12 kW/kg when the mixed softwood (MSW) was ground, while the value was as low as 0.54 kW/kg for logging residue (LOR). The lignin content ranged from 27.38 to 33.43% depending on the biomass type, and the value was the highest for LOR. The activated carbon was prepared by carbonization and activation with KOH. A partially graphitic structure was observed in the MSW by high-resolution transmission electron microscope, X-ray diffractometer, and X-ray photoelectron spectroscopy analyses. The activated carbon prepared from MSW and mixed hardwood showed higher specific surface areas (> 1832 m2/g) and micropore volume (> 0.69 cm3/g) than commercial activated carbon (1729 m2/g and 0.64 cm3/g). The gravimetric specific capacitance (17.1 F/cc) and the specific capacitance retention ratio of cycling stability (91.1%) properties were excellent in MSW. However, lignin content was not proportional to the improvement in electrochemical properties. [ABSTRACT FROM AUTHOR]

To synthesize nitrogen‐remained activated carbon (AC) following KOH activation, nitrile‐functionalized ionic liquid (IL) that immobilizes nitrogen atoms in the form of aromatic amines, such as graphitic, pyridinic, or pyrrolic nitrogen, was synthesized and used as a carbon precursor. Aromatic amines are more robust in adverse conditions than aliphatic amines. The nitrogen‐doped (N‐doped) AC was prepared by activating the carbon derived from the nitrile‐functionalized IL that acts as both a carbon precursor and a nitrogen‐doping source. The N‐doped AC had an optimized doped nitrogen and porous structure, and was prepared by controlling the activation conditions. The nitrogen residue in the N‐doped AC after KOH activation enhanced electrochemical properties of the N‐doped AC. Thus, it is important to use a carbon precursor that includes immobilized nitrogen to effectively prepare the AC after the KOH activation. [ABSTRACT FROM AUTHOR]

We report the fabrication of high-performance CNT-AC supercapacitor electrodes. CNTs are also added in the electrode preparation in this work because of high microporosity of activated carbon. The bigger ions can hardly be diffused and adsorbed onto the smaller micropores of activated carbon. The mesoporous nature of CNTs can enhance the ion adsorption through its unique and well-defined hollow core. The as prepared CNT-AC was then used as additive material to study the electrochemical properties of activated carbon based electric double layered supercapacitors (EDLCs). The physiochemical properties of CNT-AC were studied using scanning electron microscopy (SEM), Raman spectroscopic techniques, and transmission electron microscopy (TEM). Coin-type EDLC cells with two symmetrical carbon electrodes were using the synthesized carbon materials for the decrease of resistance. The electrochemical performance of the carbon electrodes was measured by galvanostatic charge/discharge and cyclic voltammetry methods. [ABSTRACT FROM AUTHOR]

We report a microwave-assisted solvothermal process for the preparation of magnetite (Fe3O4, ca. 5 nm)-anchored reduced graphene oxide (rGO). It has been examined as a prospective conversion-type negative electrode for multiple energy storage applications, such as Li-ion batteries (LIBs) and Li-ion capacitors (LICs). A LiFePO4/Fe3O4-rGO cell is constructed and capable of delivering an energy density of approximately 139 Wh kg−1 with a notable cyclability (ca. 76 %) after 500 cycles. Prior to the fabrication of a LIB, the Fe3O4-rGO is electrochemically pretreated to eliminate the irreversible capacity loss. In addition to the LIB, a high-energy LIC is also fabricated by using the pre-lithiated Fe3O4-rGO composite as the anode and commercial activated carbon as the cathode. This LIC registered a maximum energy density of approximately 114 Wh kg−1 with good cyclability. For both the LIB and LIC, the mass loading between the electrodes was adjusted based on the performance with metallic Li. The improved electrochemical performance of Fe3O4-rGO over existing materials is a promising development in the quest for novel, fast, low cost, and efficient energy storage systems without compromising the eco-friendliness [ABSTRACT FROM AUTHOR]

Cover Feature: Electrochemical Effect of Cokes-Derived Activated Carbon with Partially Graphitic Structure for Hybrid Supercapacitors (ChemElectroChem 19/2021) Hybrid supercapacitors, asymmetric supercapacitors, activated carbon, activated carbon, partially graphitic structure, Li4Ti5O12/CNT, carbon composites Keywords: hybrid supercapacitors; asymmetric supercapacitors; activated carbon; partially graphitic structure; Li4Ti5O12/CNT; carbon composites EN hybrid supercapacitors asymmetric supercapacitors activated carbon partially graphitic structure Li4Ti5O12/CNT carbon composites 3585 3585 1 10/19/21 20211001 NES 211001 B The Cover Feature b shows a strategy for optimizing the electrochemical performance of hybrid supercapacitors consisting of the cokes-derived activated carbon (CAC) and LTO/CNT electrodes. [Extracted from the article]

Carbon materials have gained considerable attention in recent years due to their superior properties. Activated carbon has been used in supercapacitors due to its density and rapid adsorption capability. The sp2–sp3 hybrid porous carbon materials are synthesized using herringbone-type carbon nanofibers (CNFs) and carbonized spherical phenol resins, with KOH as the activating agent. The morphology of the hybrid porous carbon facilitates the formation of ribbon-like nanosheets from highly activated CNFs wrapped around spherical resin-based activated carbon. The etching and separation of the CNFs produce a thin ribbon-like nanosheet structure; these CNFs simultaneously form new bonds with activated carbon, forming the sp2–sp3 hybrid porous structure. The relatively poor electrical conductivity of amorphous carbon is improved by the 3D conductive network that interconnects the CNF and amorphous carbon without requiring additional conductive material. The composite electrode has high electron conductivity and a large surface area with a specific capacitance of 120 F g−1. Thus, the strategy substantially simplifies the hybrid materials of sp2-hybridized CNFs and sp3-hybridized amorphous spherical carbon and significantly improves the comprehensive electrochemical performance of supercapacitors. The developed synthesis strategy provides important insights into the design and fabrication of carbon nanostructures that can be potentially applied as electrode materials for supercapacitors. [ABSTRACT FROM AUTHOR]

Effective pore formation in petroleum pitch (PP) is challenging because of its transformation into a stable graphitic structure at high temperatures, which is typical of soft carbon materials. This study introduces a hybrid physical activation (HPAC) process that uses steam and CO 2 as simpler alternatives. The effect of HPAC on the pore structure formation of PP was investigated, and the effects of the activator ratio and temperature on pore formation were analyzed, focusing on the specific surface area, degree of graphitization, and pore structure changes. The activated carbon achieved a maximum specific surface area of 2506 m2 g−1 through the synergistic effect of HPAC. Moreover, the milling process was crucial for the effective stabilization of PP, and controlling the ratio of steam to CO 2 optimized the pore formation. This study demonstrates that the HPAC method provides a valuable strategy for producing activated carbon from PP, and its application to various pitch materials, such as coal and wood tars, is expected to overcome the environmental pollution problems of chemical activation and the pore formation limitations of physical activation. [Display omitted] • High value-added activated carbon is manufactured from waste petroleum pitch. • Hybrid physical activation (HPAC) using steam and CO 2 was performed. • The synergistic effect of HPAC results in a specific surface area of 2506 m2 g−1. • Finding the optimal ratio of steam and CO 2 is essential to maximize pore formation. • HPAC overcomes limitations of traditional method and reduces environmental risks. [ABSTRACT FROM AUTHOR]

[Display omitted] • Partially graphitic activated carbon is manufactured from petroleum pitch. • Activated carbon achieves high gravimetric and volumetric capacitance. • Trade-off relationship between volumetric and gravimetric capacitance is addressed. • Partially graphitic structure of activated carbon generates additional capacitance. • New direction for electrode materials in supercapacitors is indicated. The volumetric and gravimetric capacitance of supercapacitors are primarily influenced by the specific surface area and porosity required for the formation of electric double layers in the electrode material, and these capacitance are known to have a trade-off relationship. To address this issue, additional capacitance enhancement mechanisms are needed not only at the electrode material surface but also within the limited mass and volume, which can be achieved through structural improvements of the material. In this study, we produce partially graphitic activated carbon with low specific surface area but nano-sized crystalline regions from petroleum pitch, a soft carbon precursor. This approach allows for improvements in gravimetric capacitance. The resulting activated carbon with a specific surface area of 1122 m2 g−1 exhibits volumetric specific capacitance of 27.9 F cc−1 and gravimetric specific capacitance of 38 F g−1 in an organic electrolyte, indicating a new direction for electrode materials in supercapacitors. [ABSTRACT FROM AUTHOR]

Schematic illustration of working mechanism of SGAC-based MFCs. • Highly porous activated carbon bioanode derived from low-cost silver-grass biomass. • Hierarchically porous architecture with co-existence of micro-, meso- and macropores. • Unprecedented surface area of 3027 m2 g−1 and pore volume of 1.3186 cm3 g−1. • Delivered maximum power of 963 mW cm−2 in MFC using E. coli as biocatalyst. • Superior biocompatibility and excellent extracellular electron transfer. In this study, highly biocompatible three-dimensional hierarchically porous activated carbon from the low-cost silver grass (Miscanthus sacchariflorus) has been fabricated through a facile carbonization approach and tested it as bioanode in microbial fuel cell (MFC) using Escherichia coli as biocatalyst. This silver grass-derived activated carbon (SGAC) exhibited an unprecedented specific surface area of 3027 m2 g−1 with the coexistence of several micro-, meso-, and macropores. The synergistic effect from pore structure (macropores — hosting E. coli to form biofilm and facilitates internal mass transfer; mesopores — favors fast electron transfer; and micropores — promotes nutrient transport to the biofilm) with very high surface area facilitates excellent extracellular electron transfer (EET) between the anode and biofilm which resulted in higher power output of 963 mW cm−2. Based on superior biocompatibility, low cost, environment-friendliness, and facile fabrication, the proposed SGAC bioanode could have a great potential for high-performance and cost-effective sustainable MFCs. [ABSTRACT FROM AUTHOR]

We propose a facile route to fabricate carbon nanotube-activated carbon composite electrodes for supercapacitor applications. The crux of our approach lies in the use of softened pitch that becomes viscous at 110 °C and combines effortlessly with multi-walled carbon nanotubes, allowing a one-pot chemical activation at 900 °C. Meso/macroscale pores created by a bundle of the nanotubes can be infiltrated effectively by the softened pitch, increasing the apparent tap density with microporosity. This composite electrode leverages the high electron conductivity of percolated multi-walled carbon nanotubes and the large surface area of activated carbon, leading to high gravimetric (11.9 Wh/kg) and volumetric energy densities (10.4 Wh/L) at 1 mA/cm2. Our method substantially simplifies the preparation of carbon nanotube-activated carbon composite materials and can be an excellent strategy to obtain practical energy storage properties at a reduced processing cost. Image 1 [ABSTRACT FROM AUTHOR]

[Display omitted] • Partially graphitic activated carbon is manufactured from petroleum pitch. • Activated carbon achieves high gravimetric and volumetric capacitance. • Trade-off relationship between volumetric and gravimetric capacitance is addressed. • Partially graphitic structure of activated carbon generates additional capacitance. Petroleum pitch (PP) is a by-product generated during the petroleum refining process, characterized by its high carbon content, tunable structure, and cost-effectiveness. These attributes have spurred extensive research into its potential as a carbon material. In this study, we prepared both untreated PP and oxidative stabilized PP (sPP) to explore the influence of pitch structural modifications on physical and electrochemical properties following carbonization and activation. Stabilizing the pitch above its softening point introduced oxygen functional groups on the surface, reaching levels of up to 19.6 at.%. These structural changes concurrently reduced aromaticity while increasing the coking value. Two types of activated carbons suitable for supercapacitors were derived from these distinct pitches, and their energy storage capacities were correlated with precursor pitch structural properties. The sPP-derived activated carbon exhibited a remarkable gravimetric specific capacitance of 39.6 F g−1, owing to its high specific surface area of 2508 m2 g−1. Conversely, PP-derived activated carbon exhibited a relatively lower specific surface area of 1122 m2 g−1. However, it demonstrated an increased electrode density and shallow ion intercalation within its graphitic structure, resulting in a notable volumetric capacitance of 26.0 F cc−1. This research not only sheds light on the electrochemical effects of pitch stabilization but also provides a foundation for the development of high-performance activated carbon materials through tailored modifications to the PP structure. [ABSTRACT FROM AUTHOR]

Porous graphitic activated carbon made from biodegradable starch-based packing peanuts contain metallic impurities, such as sodium and potassium impurities. The metallic impurities are not only eliminated in the activation process and revelation. These carbon sheets appear to form an ultrathin graphitic layer on the surface of the disordered carbon framework of the packed peanut-derived activated carbon. The shell-like graphitic structure can be explained by potassium penetration into the carbon structure during chemical activation and subsequent catalytic graphitization by the metallic impurities. These graphitic structures produce high-power density properties. As sodium impurities are present in the depth of the PP-C, it is possible to synergize the effects of potassium. The combination of these structural properties enables the carbon sheets to provide a harmonious electrochemical environment for the full realization of fast ion transport and high capacitance. Image 1 • The shell-like graphitic structure was derived from biodegradable starch-based packing peanuts. • These carbon sheets seem to form an ultrathin graphitic layer on the surface of the disordered carbon framework. • The shell-like graphitic structure is capable of creating a structure that combines the high surface area of micro/mesopores. • The shell-like graphitic structure exhibited excellent electrochemical performance. • These results should encourage the establishment of a new economic platform for advanced porous graphitic carbon. [ABSTRACT FROM AUTHOR]

We provide a method for obtaining graphitic porous carbon, with commercially viable specific capacitance and high specific surface area, from pitch pine ( Pinus rigida ) biomass. Chemically treated biomass was used to prepare porous carbon with a partially graphitic structure and high surface area via KOH activation. Biomass immersed in NH 4 OH solution was structurally separated due to swelling phenomena. It allowed for the separation of representative components comprising biomass; cellulose and hemicellulose contribute to its porous structure, while lignin contributes to the partially graphitic structure after activation. The partially graphitic porous carbon simultaneously provides electron pathway and energy storage capabilities. The biomass-derived partially graphitic porous carbon exhibited a high specific capacitance (150 F g −1 ) and high rate capability (91% at 50 mA cm −2 ), both ideal qualities for ultracapacitor materials. Effective utilization of abandoned biomass is beneficial in terms of economic, environmental, and energy saving concerns. Thus, abandoned biomass-derived partially graphitic porous carbon obtained from structurally separated components with different properties from one biomass represents a promising solution for obtaining energy efficient materials for storage devices. [ABSTRACT FROM AUTHOR]

We used multi-structured activated carbon electrodes to fabricate hybrid supercapacitors (HSCs) showing excellent electrochemical performance. As the active material, the activated carbon coupled with Li 4 Ti 5 O 12 showed a partially graphitized as well as a porous structure, and thus provided two different capacitive mechanisms: electric double layer capacitance and shallow intercalation. HSCs produced with this unique structure show excellent specific capacitances of 77 F g − 1 and 62 F cm − 3 . Partially graphitic activated carbon has great potential for HSC applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] Fluorinated activated carbon (AC) is prepared by hydrofluoric acid treatment. [•] The bonding between fluorine and carbon increases its electrical conductivity. [•] Due to this ionic bonding, fluorinated AC shows an enhanced specific capacitance. [Copyright &y& Elsevier]

Lignin is an organic polymer that is a key structural material in most plant support tissues. However, only 2% of lignin produced worldwide is commercially utilized; while the remainder is burned as fuel. It has been proven that a high carbon content and extensively bridged polymer structure are useful in creating high-value products. Herein, larch and the lignin obtained using the Klason and organosolv methods were converted into activated carbon samples for use as supercapacitors. This lignin showed higher values in carbonization yield. All other activated samples exhibited similar physical and electrochemical properties, pore structures, and surface areas. Transmission electron microscopy revealed that all samples had partially graphitic structures, which provide electron pathways and energy storage capabilities. Lignin-derived activated carbon shows the highest gravimetric specific capacitance (131 F g−1, at 1 mA cm−2), specific capacitance retention ratios of cycling stability (99% at 10 mA cm−2 for 10,000 cycles), and rate capability (91% at 30 mA cm−2). These results suggest high yield, good cycling stability, high capacitance, and eco-friendly material for supercapacitor electrodes. [Display omitted] • Lignin derived from raw and treated larch have similar physical and electrochemical properties. • Raw larch and its extracted lignins exhibit partially graphitized structures after chemical activation. • Both raw larch and its extracted lignins show high retention rates of specific capacitance. [ABSTRACT FROM AUTHOR]