Regulation of nitrogen species on biomass-based porous activated carbon surfaces by varying nitrogen sources for high-performance supercapacitors

Abstract

Nitrogen-doped porous carbon materials derived from agricultural waste are considered ideal for supercapacitor applications. However, current research is limited to nitrogen doping, with insufficient analysis of the effects of different nitrogen species on capacitor performance. This study compares four different nitrogen sources, revealing that the MN-AC electrode material, prepared using melamine as the nitrogen source, effectively enhances the physicochemical structure and electrochemical performance of the electrode. It exhibits the highest surface nitrogen content (4.54 %) and an optimal mesopore rate (20.6 %), with a significant amount of pyrrole nitrogen (53.19 % of the surface content), which notably improves the material's polarization and wettability, thereby enhancing its electrochemical performance. At a current density of 0.5 A g⁻¹, MN-AC demonstrates a high specific capacitance of 349.3 F g⁻¹. Furthermore, in a 6 M KOH electrolyte, it achieves an energy density of 20.3 Wh kg⁻¹ and a power density of 169 W kg⁻¹. DFT analysis indicates that pyrrole nitrogen increases the material's dipole moment, enhancing the adsorption of electrolyte ions (K⁺).