N-Doped Mesoporous Carbon Prepared from a Polybenzoxazine Precursor for High Performance Supercapacitors

Supercapacitors store energy either by ion adsorption or fast surface redox reactions. The capacitance produced by the former is known as electrochemical double layer capacitance and the latter is known as pseudo-capacitance. Carbon materials are found to be attractive materials for energy storage, due to their various micro-structures and wide source of availability. Polybenzoxazine (Pbz) is used as a source to produce carbon materials, due to the fact that the obtained carbon will be rich in N and O species for enhanced performance. Moreover, the carbon materials were produced via template-free method. In general, activation temperature plays a main role in altering the porosity of the carbon materials. The main purpose of this study is to find the suitable activation temperature necessary to produce porous carbons with enhanced performance. Considering these points, Pbz is used as a precursor to produce nitrogen-doped porous carbons (NRPCs) without using any template. Three different activation temperatures, namely 700, 800 and 900 °C, are chosen to prepare activated porous carbons; NRPC-700, NRPC-800 and NRPC-900. Hierarchical micro-/ meso-/macropores were developed in the porous carbons with respect to different activation temperatures. PBz source is used to produce carbons containing heteroatoms and an activation process is used to produce carbons with desirable pore structures. The surface morphology, pore structure and binding of heteroatoms to the carbon surface were analyzed in detail. NRPCs produced in this way can be used as supercapacitors. Further, electrodes were developed using these NRPCs and their electrochemical performance including capacitance, specific capacitance, galvanic charge/discharge, impedance, rate capability are analyzed. The obtained results showed that the activation temperature of 900 °C, is suitable to produce NRPC with a specific capacitance of 245 F g^-1 at a current density of 0.5 A g^-1, that are attributed to high surface area, suitable pore structure and presence of heteroatoms.