Nanostructured adsorbents carbon nanotubes

Carbon-based adsorbents such as activated carbons, carbon nanotubes, and carbon nanofibres have been the subject of intensive research over the past 15 years. The research on hydrogen storage in carbon materials was dominated by announcements of extraordinary high storage capacities in carbon nanostructures. 

In the Pt-doped hexagonal mesophase formed from CPCI (cetyl pyridinium chloride), platinum ions are adsorbed at the surface of the surfactant cylinders. They are reduced radiolytically into a metal layer as a nanotube of around 10 nm diameter and a few hundred nm long (Fig. 3f). Extraction of all these nanostructures is achieved by dissolution of the soft template using alcohol. This possible easy extraction constitutes a marked advantage over the synthesis in hard templates, such as mesoporous silica or carbon nanotubes, the dissolution of which is more hazardous for the metal nanostructures. 

Carbon nanotube (CNT) is another kind of hard template. After surface modification, GNTs can adsorb OH" or Ce(III, FV) ions at the surface, which result in ID ceria nanostructures after precipitation and calcination to remove the template. 

Comparatively to nanotubes, nanofibers present a nanostructure made of grapheme layer stacking which is favorable to activation. Two activation systems can be used for activated carbon nanofibers physical activation by CO2 or heat, and chemical activation by KOH or RbOH [134,135]. A range of potential adsorbents was thus prepared by varying the temperature and time of activation. The structure of the CNF proved more suitable to activation by KOH than by CO, with the former yielding higher surface area carbons (up to 1000 m g ). 

However, the electrodes which are used in supercapacitors have far more complex topologies than planar surfaces. The nanoporous carbons, such as the nanotubes, " cluster-assembled nanostructured carbons, nano-onions or carbide-derived nanoporous carbons have surfaces which are mostly curved, and can also contain many topological defects. It is important to understand how this impacts the structure of the adsorbed electrolytes and the resulting capacitance of the interface, even in the absence of confinement effects. 

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