Enhanced supercapacitor and capacitive deionization boosted by constructing inherent N and P external defects in porous carbon framework with a hierarchical porosity

Heteroatom-doped porous carbon frameworks have attracted extensive attention as high-performance electrodes for capacitive applications. While their further development is still restricted by the inevitable concurrent dopant leaching effect and structural collapse during the high-temperature pyrolysis process . Therefore, developing a straightforward method for the synthesis of carbons simultaneously with plentiful multiple external defects and rational porous structure to satisfy high-performance capacitive applications is still a tremendous challenge. Herein, an emerging plerogyra sinuosa-like hierarchically porous carbon with plentiful N/P external defects is firstly prepared via an effective and in-site carbonization process, which shows great promise for supercapacitor and capacitive deionization applications. Due to the efficient N and P synergistic effects and 3D connected framework with prolific meso-microporous structure, the optimized carbon exhibits a large specific capacitance of 337 F g −1 at a current density of 1 A g −1 and maintains 239 F g −1 at 100 A g −1 in 6.0 M KOH electrolyte. For capacitive deionization tests, the carbon shows an excellent salt adsorption capacity of 19.3 mg g −1 in NaCl solution with a concentration of 500 mg L −1 at an applied voltage of 1.2 V. While from the kinetics analysis and density functional theory, we find that the coupling of multiple external defects has a positive influence on the distribution of electron density and surface condition, which is greatly beneficial to pseudocapacitance, quantum capacitance and the electrolyte-adsorption capacity. This work provides a new route for the preparation of emerging heteroatom-doped hierarchically porous carbon frameworks for further advanced applications such as water treatment, electrocatalysis , as well as energy storage.