Activated Carbons and Their Evaluation in Electric Double Layer Capacitors.

This review presents a summary of the manufacturing of activated carbons (ACs) as electrode materials for electric double layer capacitors. Commonly used techniques of open and closed porosity determination (gas adsorption, immersion calorimetry, X-ray and neutrons scattering) were briefly described. AC production methods (laboratory and industrial) were detailed presented with the stress on advantages and drawbacks of each ones in the field of electrode materials of supercapacitor. We discussed all general parameters of the activation process and their influence on the production efficiency and the porous structure of ACs. We showed that porosity development of ACs is not the only factor influencing capacity properties. The role of pore size distribution, raw material origin, final carbon structure ordering, particles morphology and purity must be also taken into account. The impact of surface chemistry of AC was considered not only in the context of pseudocapacity but also other important factors, such as inter-particle conductivity, maximal operating voltage window and long-term stability.

Well-Designed Porous Graphene Flakes for Lithium-Ion Batteries with Outstanding Rate Performance.

Porous graphene flakes (PGFs) with controllable pore sizes are selectively prepared through self-assembly of Fe3O4 nanoparticles on organic modified montmorillonite combined with carbonization and subsequent annealing treatment. The resulting PGFs with a thickness of 5 nm have a specific surface area of 337 m2/g, pore volume of 0.66 cm3/g, and mean pore diameter of 15 nm. Due to their unique porous flake structures, PGFs show an impressive rate performance in lithium-ion batteries, especially at high current densities (238 mA h/g at 10 C) as well as long-term stability in comparison to the commercial graphite (55 mA h/g at 10 C). Therefore, PGFs with their key structural properties serve as ideal candidates as electrode components in lithium-ion batteries and show great potential application in other energy storage fields.

Mass production of hierarchically porous carbon nanosheets by carbonizing "real-world" mixed waste plastics toward excellent-performance supercapacitors.

Recently, sustainable development and serious energy crisis called for appropriate managements for the large number of municipal and industrial waste plastics as well as the development of low-cost, advanced materials for energy storage. However, the complexity of waste plastics significantly hampers the application of ever used methods, and little attention is paid to the utilization of waste plastics-derived carbon in energy storage. Herein, porous carbon nanosheets (PCNSs) was produced by catalytic carbonization of "real-world" mixed waste plastics on organically-modified montmorillonite (OMMT) and the subsequent KOH activation. PCNSs was featured on hierarchically micro-/mesoporous structures with the pore size distribution centered on 0.57, 1.42 and 3.63 nm and partially exfoliated graphitic layers, and showed a high specific surface area of 2198 m2 g-1 and a large pore volume of 3.026 cm3 g-1. Benefiting from these extraordinary properties, PCNSs displayed a superior performance for supercapacitors with high specific capacitances approaching 207 and 120 F g-1 at a current density of 0.2 A g-1 in aqueous and organic electrolytes, respectively. Importantly, when the current density increased to 10 A g-1, the specific capacitances remained at 150 F g-1 (72.5%) and 95 F g-1 (79.2%) in aqueous and organic electrolytes, respectively. The outstanding rate capability of PCNSs was in sharp contrast to the performance of traditional activated carbons. This work not only provides a potential way to recycle mixed waste plastics, but also puts forward a facile sustainable approach for the large-scale production of PCNSs as a promising candidate for supercapacitors.

Electrochemical characteristics of discrete, uniform, and monodispersed hollow mesoporous carbon spheres in double-layered supercapacitors.

Core-shell-structured mesoporous silica spheres were prepared by using n-octadecyltrimethoxysilane (C18TMS) as the surfactant. Hollow mesoporous carbon spheres with controllable diameters were fabricated from core-shell-structured mesoporous silica sphere templates by chemical vapor deposition (CVD). By controlling the thickness of the silica shell, hollow carbon spheres (HCSs) with different diameters can be obtained. The use of ethylene as the carbon precursor in the CVD process produces the materials in a single step without the need to remove the surfactant. The mechanism of formation and the role played by the surfactant, C18TMS, are investigated. The materials have large potential in double-layer supercapacitors, and their electrochemical properties were determined. HCSs with thicker mesoporous shells possess a larger surface area, which in turn increases their electrochemical capacitance. The samples prepared at a lower temperature also exhibit increased capacitance as a result of the Brunauer-Emmett-Teller (BET) area and larger pore size.

Nanoconfinement induced formation of core/shell structured mesoporous carbon spheres coated with solid carbon shell.

A novel method for the fabrication of core/shell structured mesoporous carbon spheres with solid shell using a template method has been presented. The unique molecular nanostructures are characterized by XRD, TEM, TGA, and nitrogen adsorption/desorption measurement. The formation mechanism of the mesostructured carbon spheres with a carbon shell is proposed according to the experimental results. Nanoconfinement effect, occurring in the core/shell structured template, is believed to play a key role in mediating the formation of these hierarchical carbon mesostructures, with SnO2 as a template and C2H4 as a carbon source of a mesoporous carbon core. This synthesis method is simple, straightforward, and suitable for the preparation of various nanostructures that are unique scaffolds in catalytic and electrochemical applications.

Template method synthesis of mesoporous carbon spheres and its applications as supercapacitors.

Mesoporous carbon spheres (MCS) have been fabricated from structured mesoporous silica sphere using chemical vapor deposition (CVD) with ethylene as a carbon feedstock. The mesoporous carbon spheres have a high specific surface area of 666.8 m2/g and good electrochemical properties. The mechanism of formation mesoporous carbon spheres (carbon spheres) is investigated. The important thing is a surfactant hexadecyl trimethyl ammonium bromide (CTAB), which accelerates the process of carbon deposition. An additional advantage of this surfactant is an increase the yield of product. These mesoporous carbon spheres, which have good electrochemical properties is suitable for supercapacitors.