Nitrogen configuration modulation of porous graphitic carbon nanosheets for superior capacitive energy storage

Carbon nanosheets with layer-stacked porous structures and surface functionalized groups are beneficial for efficient ion storage in supercapacitor electrode materials, but achieving high cost-effectiveness and controllable surface groups remains a significant challenge. Herein, the biomass-derived chitosan and sodium alginate are selected as raw materials for self-assembly reaction with phytic acid as a cross-linking agent. The protonated chitosan and sodium alginate form a cross-linked network structure through hydrogen bonding and electrostatic adsorption, which is subsequently carbonized and activated to synthesize porous graphitic carbon nanosheets (PNPCN-X). PNPCN-X realizes an efficient distribution of porous and graphitic structures. It's noteworthy that phytic acid facilitates the fixation of N atoms, and various N configurations can be adjusted by altering the content of phytic acid. Optimized PNPCN-1.5 exhibits a high content of structurally stable pyridinic-N and graphitic-N configurations, which are confirmed to serve as active sites substantially augmenting the ion adsorption capacity through Density Functional Theory (DFT) calculations. Benefiting from its exceptional physicochemical properties, PNPCN-1.5 achieves 322 F g −1 as electrode materials in the three-electrode system, while the symmetrical supercapacitor assembled with EMIMBF 4 electrolyte attains 56.29 W h kg −1 . Furthermore, various kinetic analyses extensively elucidate its capacitance distribution characteristics and ion diffusion rates.