Nanocomposites and nanomaterials
Nitrogen-doped carbon for supercapacitors: synthesis, properties and applications
Maksymych V.1, Calus D.2, Borysiuk A.1, Chabecki P.2, Ivashchyshyn F.1,2
1 Department of Applied Physics and Nanomaterials Science, Lviv Polytechnic National University, S. Bandera st. 12, 79013 Lviv, Ukraine
E-mail: vitalii.m.maksymych@lpnu.ua
2 Faculty of Electrical Engineering, Czestochowa University of Technology,
J.H. Dąbrowskiego st., 69, 42-201 Częstochowa, Poland

The key to success in increasing the specific capacity of nanoporous carbons, which are used for the manufacture of supercapacitor electrodes, is to ensure the combination of optimal porous structure with the appropriate electronic structure of the material. This would ensure the release of the Helmholtz capacitance by the capacitance of the space charge region in the solid. Therefore, the aim of this work was to obtain nitrogen-doped environmentally safe nanoporous carbon material.
Nitrogen-containing carbon material was obtained by direct pyrolysis method. Glucose was used as a carbon source, sodium bicarbonate as an activator (porogen) and urea as a nitrogen source for carbon doping. 
The resulting carbon material is characterized by high homogeneity as evidenced by the images taken on the Phenom ProX scanning electron microscope. The nitrogen content of the EDS analysis system ranged from 2.88% to 25.17 wt.%. According to the results of nitrogen adsorption-desorption received the maximum pore distribution in the radius corresponds to 1.42 nm, and the total surface area reaches 1247 m2/g. The results of X-ray low-angle scattering confirm the obtained result of porometry, which indicates the openness of the pores and their availability to the electrolyte. Unexpectedly, in the process of studying the carbon material, its magnetization was revealed. The method of vibration magnetometry established that the specific saturation magnetization of carbon material in the magnetic field strength of 800 kA/m is σs = 1.4 А∙m2∙kg-1, and the coercive force Hc = 10 kA/m. The method of impedance spectroscopy confirmed the relatively high electrical conductivity of carbon material. It was found that in a symmetrical supercapacitor with 30% water solution KOH electrolyte, the specific capacity of the obtained carbon material reaches 180 F/g, which is 80% higher compared to the existing on the market materials.