N-Doped rGO-Like Carbon Prepared from Coconut Shell: Structure and Specific Capacitance

An rGO−like carbon compound has been synthesized from biomass, i.e., old coconut shell, by a carbonization process followed by heating at 400°C for 5 h. The nitrogen doping was achieved by adding the urea (CH₄N₂O) and stirring at 70°C for 14 h. The morphology and structure of the rGO-like carbon were investigated by electron microscopies and Raman spectroscopy. The presence of C-N functional groups was analyzed by Fourier trans-form infrared and synchrotron X-ray photoemission spectroscopy, while the particle and the specific capacitance were measured by particle sizer and cyclic voltammetry. The highest specific capacitance of 72.78 F/g is achieved by the sample with 20% urea, having the smallest particles size and the largest surface area. The corresponding sample has shown to be constituted by the appropriate amount of C–N pyrrolic and pyridinic defects.