Please cite this article as: Mostazo-López, M.J., Ruiz-Rosas, R., Morallón, E., Cazorla-Amorós, D., Generation of nitrogen functionalities on activated carbons by amidation reactions and Hofmann rearrangement: chemical and electrochemical characterization, Carbon (2015), doi: http://dx.
AbstractNitrogen functionalization of a highly microporous activated carbon (BET surface area higher than 3000 m 2 /g) has been achieved using the following sequence of treatments: (i) chemical oxidation using concentrated nitric acid, (ii) amidation by acyl chloride substitution with NH 4 NO 3 and (iii) amination by Hoffman rearrangement. This reaction pathway yielded amide and amine functional groups, and a total nitrogen content higher than 3 at%. It is achieved producing only a small decrease (20%) of the starting microporosity, being most of it related to the initial wet oxidation of the activated carbon. Remarkably, nitrogen aromatic rings were also formed as a consequence of secondary cyclation reactions. The controlled step-by-step modification of the surface chemistry allowed to assess the influence of individual nitrogen surface groups in the electrochemical performance in 1M H 2 SO 4 of the carbon materials. The largest gravimetric capacitance was registered for the pristine activated carbon due to its largest apparent surface area. The nitrogen-containing activated carbons showed the highest surface capacitances. Interestingly, the amidated activated carbon showed the superior capacitance retention due to the presence of functional groups (such as lactams, imides and pyrroles) that enhance electrical conductivity through their electron-donating properties, showing a capacitance of 83 F/g at 50 A/g. 399.8 ± 0.2 Amide, Lactam, Amine, Imide 1.89 50 398.8 ± 0.2 Pyridine, Imine 1.17 31 KUA-NH 2 400.5 ± 0.2 Pyrrole, Pyridone 0.72 27 399.6 ± 0.2 Amide, Lactam, Amine, Imide 1.25 48 398.5 ± 0.2 Pyridine, Imine 0.65 25 KUA-CONH 2 after TPD 398.4 ± 0.2 Pyridine 0.55 49 400.6 ± 0.2 Pyrrole, Pyridone 0.57 51 KUA-NH 2 after TPD 398.3 ± 0.2 Pyridine 0.42 31 400.2 ± 0.2 Pyrrole, Pyridone 0.92 69