Various activated carbons (ACs) of different oxygen contents were treated with NH₃ gas at 700°C (7AGs) to introduce nitrogen species on the graphene layers for metal ion removal in aqueous solution. The nitrogen content increased with increasing oxygen content of the precursor. The AC was also outgassed in He flow at 1000°C (OG) to remove surface functional groups, and was compared with 7AGs. The amount of Cu(II) adsorption increased with increasing nitrile, pyridine and secondary or tertiary amine groups, which have a lone electron pair. Equilibrium pH decreased with increase in total nitrogen content. It is known that Cu(II) makes a very stable complex regardless of the ligand species and that the solution pH decreases as the complex stability increases. Therefore free basic nitrogen such as nitrile-N can affect the Cu(II) adsorption property of the ligand. Because positively charged quaternary-N has no lone pair, it adsorbs neither Cu(II) nor the proton. Thus the solution pH was influenced by quaternary-N in addition to free base nitrogen. Adsorption affinities and amounts of Cu(II) adsorbed on 7AGs were greater than those of OG, while amounts of Cu(II) desorbed from 7AGs were smaller than OG. Consequently Cu(II)-N binding was considered to be stronger than the Cu(II)-Cπ interaction.

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Dehalogenation of chlorophenol to give chloride ion had been found to take place in an aqueous solution by contact with high temperature He-treated activated carbons (ACs). In the present study, the influence of the surface chemistry of activated carbon and solution pH was examined to study the dehalogenation mechanism. The dehalogenation reaction was inhibited by electron-withdrawing groups and by nitrogen introduced on the graphite edge on ACs, whereas the reaction took place for ACs that had been outgassed and introduced to electron-donating groups. In addition, the greater the increase in pH, the greater the dehalogenation for the outgassed ACs.

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The physicochemical properties of carbon materials are strongly influenced by the presence of chemical species on the surface. In this study, surface functional groups on cup-stacked-type carbon nanotubes (CSCNTs) were introduced by gas phase, liquid phase, and electrochemical oxidations. Several techniques were used to characterize these materials including nitrogen adsorption, chemical and thermal analyses, FT-IR, XPS, SEM, TEM, and Raman. The results indicated that the amount of surface functional groups on CSCNTs was strongly affected by the oxidation method. In particular, the electrochemical oxidation of CSCNTs was effective and increased the concentration of carboxylic acid.

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Studies on MgO-templated carbons were reviewed, focusing on the importance of the pores, particularly mesopores, in their applications. Mesopores were formed to inherit their size and morphology from MgO particles and so could be controlled by the selection of the MgO precursor. The formation of micropores depended on the carbon precursors and apparently on the carbonization conditions. By selecting the carbon precursor, nitrogen-containing porous carbons were prepared. By adding metal compounds of Sn and Pt, fine particles of the metal could be highly dispersed in the carbon. Using the materials as electrodes in electrochemical capacitors with aqueous and non-aqueous electrolytes, mesopores formed in MgO-templated carbons were confirmed to have an important role in achieving a high rate performance. Through the construction of asymmetric capacitors from mesoporous MgO-templated carbons as one of electrodes, a predominant contribution of the negative electrode to the capacitive performance was shown in a (C₂H₅)₃(CH₃)NBF₄/PC electrolyte. MgO-templated carbon containing fine particles of metallic Sn was used successfully as the anode of lithium ion rechargeable batteries, where the space adjacent to Sn particles in mesopores seemed to absorb a large volume expansion due to alloying of Sn with Li. Mesoporous MgO-templated carbon could adsorb a large amount of gasoline vapor, which was comparable to its mass. The possibility of extending the MgO template process to the production of large amounts of nanoporous carbons was discussed on the basis of its advantages.

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