Generation of nitrogen functionalities on activated carbons by amidation reactions and Hofmann rearrangement: Chemical and electrochemical characterization

Abstract

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

Nitrogen doped superporous carbon prepared by a mild method. Enhancement of supercapacitor performance

“…The changes in surface chemistry on the sample KUA-CONH2 have been previously studied [11], and we found that this increase in oxygen was related to the chemical oxidation treatment carried out prior to amidation step. In case of KUA-N, TPD measurements show a relevant decrease in the CO-evolving groups, with a net total decrease (490 µmol /g) that is especially relevant in the region of thermal decomposition of phenol and quinone-like groups.…”

“…In our previous work [11], an approach for the incorporation of amides over activated carbon was satisfactorily developed. Also, other nitrogen functional groups were introduced on the surface of the carbon material via secondary reactions.…”

“…[6,9]. However, these approaches are usually carried out at high temperatures and, in the case of post-treatments, these conditions strongly modify the porosity of the pristine carbon material [10,11]. Also, the control of the nitrogen functionalities that are formed during post-treatments is a challenge.…”

“…In our previous work [11], we proposed the modification of the surface chemistry of a highly porous activated carbon using organic chemistry reactions. Briefly, this treatment consisted in the oxidation of the carbon material in order to introduce oxygen functionalities that, afterwards, were converted into nitrogen functionalities through an amidation treatment.…”

Successful functionalization of superporous zeolite templated carbon using aminobenzene acids and electrochemical methods

“…Electrochemical techniques have been successfully used for the covalent and non-covalent functionalization of different carbon materials with nitrogen functional groups [21], [22] and polymers [23], [24]. The modification of carbon nanotubes using 4-aminobenzoic acid (4-ABA), 4-aminobenzenesulfonic acid (4-ABSA) and 4-aminobenzylphosphonic acid (4-ABPA) in aqueous solution, is an illustrative example of the potential of this method to functionalize with different heteroatoms [8], [25]- [27].…”