Carbon materials have attracted intense interests as electrode materials for electrochemical capacitors, because of their high surface area, electrical conductivity, chemical stability and low cost. Activated carbons produced by different activation processes from various precursors are the most widely used electrodes. Recently, with the rapid growth of nanotechnology, nanostructured electrode materials, such as carbon nanotubes and template-synthesized porous carbons have been developed. Their unique electrical properties and well controlled pore sizes and structures facilitate fast ion and electron transportation. In order to further improve the power and energy densities of the capacitors, carbon-based composites combining electrical double layer capacitors (EDLC)-capacitance and pseudo-capacitance have been explored. They show not only enhanced capacitance, but as well good cyclability. In this review, recent progresses on carbon-based electrode materials are summarized, including activated carbons, carbon nanotubes, and template-synthesized porous carbons, in particular mesoporous carbons. Their advantages and disadvantages as electrochemical capacitors are discussed. At the end of this review, the future trends of electrochemical capacitors with high energy and power are proposed.

Porous carbon materials are of interest in many applications because of their high surface area and physicochemical properties. Conventional syntheses can only produce randomly porous materials, with little control over the pore-size distributions, let alone mesostructures. Recent breakthroughs in the preparation of other porous materials have resulted in the development of methods for the preparation of mesoporous carbon materials with extremely high surface areas and ordered mesostructures, with potential applications as catalysts, separation media, and advanced electronic materials in many scientific disciplines. Current syntheses can be categorized as either hard-template or soft-template methods. Both are examined in this Review along with procedures for surface functionalization of the carbon materials obtained.

By creating nanoscale pores in a layer of graphene, it could be used as an effective separation membrane due to its chemical and mechanical stability, its flexibility and, most importantly, its one-atom thickness. Theoretical studies have indicated that the performance of such membranes should be superior to state-of-the-art polymer-based filtration membranes, and experimental studies have recently begun to explore their potential. Here, we show that single-layer porous graphene can be used as a desalination membrane. Nanometre-sized pores are created in a graphene monolayer using an oxygen plasma etching process, which allows the size of the pores to be tuned. The resulting membranes exhibit a salt rejection rate of nearly 100% and rapid water transport. In particular, water fluxes of up to 10(6) g m(-2) s(-1) at 40 °C were measured using pressure difference as a driving force, while water fluxes measured using osmotic pressure as a driving force did not exceed 70 g m(-2) s(-1) atm(-1).

We show that graphene chemical vapor deposition growth on copper foil using methane as a carbon source is strongly affected by hydrogen, which appears to serve a dual role: an activator of the surface bound carbon that is necessary for monolayer growth and an etching reagent that controls the size and morphology of the graphene domains. The resulting growth rate for a fixed methane partial pressure has a maximum at hydrogen partial pressures 200-400 times that of methane. The morphology and size of the graphene domains, as well as the number of layers, change with hydrogen pressure from irregularly shaped incomplete bilayers to well-defined perfect single layer hexagons. Raman spectra suggest the zigzag termination in the hexagons as more stable than the armchair edges.

Perovskite oxides are attractive candidates as catalysts for the electrolysis of water in alkaline energy storage and conversion systems. However, the rational design of active catalysts has been hampered by the lack of understanding of the mechanism of water electrolysis on perovskite surfaces. Key parameters that have been overlooked include the role of oxygen vacancies, B-O bond covalency, and redox activity of lattice oxygen species. Here we present a series of cobaltite perovskites where the covalency of the Co-O bond and the concentration of oxygen vacancies are controlled through Sr 2 þ substitution into La 1 À x Sr x CoO 3 À d . We attempt to rationalize the high activities of La 1 À x Sr x CoO 3 À d through the electronic structure and participation of lattice oxygen in the mechanism of water electrolysis as revealed through ab initio modelling. Using this approach, we report a material, SrCoO 2.7 , with a high, room temperature-specific activity and mass activity towards alkaline water electrolysis.

We investigate the permeability and selectivity of graphene sheets with designed subnanometer pores using first principles density functional theory calculations. We find high selectivity on the order of 10(8) for H(2)/CH(4) with a high H(2) permeance for a nitrogen-functionalized pore. We find extremely high selectivity on the order of 10(23) for H(2)/CH(4) for an all-hydrogen passivated pore whose small width (at 2.5 A) presents a formidable barrier (1.6 eV) for CH(4) but easily surmountable for H(2) (0.22 eV). These results suggest that these pores are far superior to traditional polymer and silica membranes, where bulk solubility and diffusivity dominate the transport of gas molecules through the material. Recent experimental investigations, using either electron beams or bottom-up synthesis to create pores in graphene, suggest that it may be possible to employ such techniques to engineer variable-sized, graphene nanopores to tune selectivity and molecular diffusivity. Hence, we propose using porous graphene sheets as one-atom-thin, highly efficient, and highly selective membranes for gas separation. Such a pore could have widespread impact on numerous energy and technological applications; including carbon sequestration, fuel cells, and gas sensors.

Filling the pores: A zinc‐based metal–organic framework (MOF) can be transformed reversibly from an open (a) to a dense (b) configuration. The microporous solid is the first example of a MOF that is highly selective in the gas‐chromatographic separation of alkanes.

Elemental carbon materials exhibit unique electronic, mechanical, and chemical properties that make them attractive, for example, for nanoelectronic devices, [1] strengthenhancing materials, [2] separation media, [3][4][5][6] catalyst supports, [7] energy storage/conversion systems, [8] proximal probes, [9] optical components. [10] Well-defined nanoporous carbon materials are essential for a number of these applications. Ordered porous carbon materials have previously been replicated by using colloidal crystals [10] and presynthesized mesoporous silicas as scaffolds.[7] These methodologies are extremely difficult to adapt to the fabrication of large-scale ordered nanoporous films with controlled pore orientations. Although numerous methods (e.g., chemical vapor deposition, [11] ultrasonic deposition, [3a] silica template synthesis, [3b, 7] hydrothermal decomposition of carbide compounds, [12] and polymer coating and pyrolysis [13] ) have been developed for the fabrication of carbon films, no ordered nanoporous carbon films have been obtained with such methods. Accordingly, the large-scale alignment of the carbon nanostructural films is still a big challenge. Herein, we demonstrate a stepwise self-assembly approach to the preparation of large-scale, highly ordered nanoporous carbon films. The carbon precursor molecules are spatially arranged into well-defined nanostructures by the self-assembly of block copolymers (BCPs). A hexagonally packed carbon-channel array whose orientation is normal to the carbon film surface has been successfully synthesized. Large-scale crack-free carbon films of up to 6 cm 2 can be readily fabricated on common substrates such as silica, copper, silicon, and carbon.The self-assembly of BCPs has proven to be a versatile approach to the selective organization and nanoscale regulation of the concentration distribution of target molecular species for the fabrication of nanoporous materials. [14][15][16] The mechanism for such organization involves hydrogen-bonding, [17] ion-pairing, [18] and/or dative interactions [19] between supramolecular assemblies of BCPs and target molecular species. The resulting composites can give rise to various nanostructures according to the structural and phase behaviors of the BCPs. The target molecular species are spatially concentrated in selected microdomains and can eventually serve as nanostructured catalysts, [20] spacers, [21] or precursors [22] for the further fabrication of ordered nanostructures. Highly ordered nanoporous materials, such as polymer, [22] silica, [23,24] and organic-inorganic hybrid materials, [25,26] have been created through polymerization in the presence of the self-assembled BCPs.Although BCPs contain high atomic carbon concentrations, ordered nanoporous carbon films have not been successfully fabricated through the direct pyrolysis of selfassembled BCPs.[27] This inability is attributed to the fact that linearly structured BCP compounds have very poor carbon yields in carbonization reactions. Furthermore, the survival of the nan...