On the origin of the high capacitance of nitrogen-containing carbon nanotubes in acidic and alkaline electrolytes

Abstract

The preparation of nitrogenated carbon nanotubes (N-CNT) using pyridine as a carbon precursor resulted in an eight-times increase in gravimetric capacitance.

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

“…As can be seen, KUA-CONH2 Table 1) this difference cannot be explained by diffusional problems along the porosity. Then, the improvement found for KUA-N should be related to the generation of electron-donor nitrogen functionalities [8] or to the decrease of detrimental electron-withdrawing oxygen groups improving the conductivity of the material. This positive effect of the conversion of oxygen groups into nitrogen functionalities is not observed in KUA-CONH 2 due to the previous generation of a large amount of carboxylic acids during the oxidation treatment with nitric acid.…”

“…Likewise, the presence of nitrogen on the surface of activated carbons improves the performance of activated carbon as electrodes of supercapacitors by increasing the wettability of the surface, the electrochemical stability, the conductivity or the contribution of pseudocapacitive processes [5][6][7][8]. Inversely to the ubiquity of surface oxygen groups, nitrogen functionalities are not as easily introduced in the structure of carbon materials, and the development of new procedures for obtaining nitrogencontaining porous carbons has therefore attracted a great interest.…”

“…The modification protocol allowed the incorporation of different nitrogen functionalities. Interestingly, this method also leads to the formation of pyridines, pyridones and pyrroles, which have a positive impact in the electrochemical behavior of carbon materials [6,8], but are only introduced using high temperature treatments. However, the oxidation treatment carried out during the first step of the functionalization protocol produced a remarkable decrease of the microporosity along with the generation of non-desirable functional groups (CO 2 -evolving groups) from the point of view of the capacitor performance.…”

Electrochemical behaviour of activated carbons obtained via hydrothermal carbonization

“…It was pointed out that pyridinic nitrogen and pyrrolic nitrogen were the most effective in a double layer formation while quaternary-N and pyridinic-N-oxides improved the capacitance due to their positive charge [43]. Moreover, the nitrogen groups showed an enhancement in the capacitance in neutral and basic electrolytes [15,26,44].…”

“…Moreover, it was demonstrated that this high nitrogen amount prevails even after the chemical activation. It is known that nitrogen groups change the electrochemical properties, such as electron-donor character, conductivity and capacitance behavior [9,[24][25][26]. The improvement of these electrochemical properties together with the control of the porous texture, would give suitable carbon materials to enhance the capacitors performance.…”