Heteroatom-Enriched\nCarbon Particles Derived from\nMultifunctional Polybenzoxazine Particles for High-Performance Supercapacitors

The rational molecular engineering of a heteroatom-enriched\npolymer\nprecursor to achieve inherently doped carbon material is of crucial\nimportance for advanced applications. In the present work, the molecular-design\nflexibility of polybenzoxazine is utilized to fabricate a N, O-codoped\ncarbon framework using a facile template-free extended sol–gel\nmethod using phloroglucinol, polyethylenimine, and formaldehyde as\nmultifunctional precursors. The uniform spherical morphology of the\npolymeric particles was attained by the careful tuning of the reactant\nstoichiometric ratio, precursor concentration, and solvent ratio in\nthe reaction medium to control the kinetics of particle formation.\nThe corresponding heteroatom-doped carbon spheres with 28% nitrogen\nand 20.5% oxygen determined using CHNS analysis were attained by subjecting\nthe polybenzoxazine particles to moderate carbonization conditions,\nresulting in the formation of a partial graphitic structure. The carbon\nstructure with a moderate BET surface area of 221 m<sup>2</sup> g<sup>–1</sup> and high heteroatom content makes it a potential\ncandidate for electrochemical energy storage. The electrochemical\nperformance as a supercapacitor was evaluated using a three-electrode\nsystem where the doped carbon displayed an excellent specific capacitance\nof 728 F g<sup>–1</sup> at 10 A g<sup>–1</sup> current\ndensity in 0.1 M H<sub>2</sub>SO<sub>4</sub> electrolyte, resulting\nin a high energy density of 56 W h kg<sup>–1</sup> and power\ndensity of 14246 W kg<sup>–1</sup>. The electrochemical performance\nwas further evaluated by using a flexible all-solid-state symmetric\ntwo-electrode system to simulate real-time analysis. The active material\ndisplayed an appreciable specific capacitance of 50.3 F g<sup>–1</sup> at 0.2 A g<sup>–1</sup>. In addition, capacitance retention\nof ∼86% after 2500 cycles in the asymmetric two-electrode configuration\nalso confirmed the reversible nature of the device, with negligible\nchanges in the resistance values obtained before and after the cyclic\ntests. The as-synthesized multifunctional precursor-based polybenzoxazine\nparticles for fabrication of N, O-codoped carbon framework presents\nitself as a promising active material for fabrication of supercapacitor\nelectrodes.