Design and theoretical study of carbon-based supercapacitors especially exhibiting superior rate capability by the synergistic effect of nitrogen and phosphor dopants

Abstract Carbonaceous materials have long been a key component of supercapacitor energy storage systems, and exploring heteroatom doping and its role is currently the focus of carbon-based electrode development. Here, a method of in-situ doping a phosphorus atom into a nitrogen-containing hierarchical porous carbon nanosheet is proposed, which is realized by a self-synthesis and template-assisted assembly process. Phosphorus-doping improves the wettability of the carbon material and produces defects that expose more active sites, which facilitates charge transfer of the electrode material as a whole and at the interface. Density functional theory calculations proves that P-doping improves the affinity and ionic adsorption of the carbon surface, thereby increasing the specific capacitance (242 F g−1) and rate capability (70.8%). The synergistic effect of N/P co-doping provides rapid interfacial ion adsorption reactions that further improve electrochemical performance, including power density (15 kW kg−1) and high energy density (34.4 Wh kg−1) and ultra-high cycle stability (91.4%). This work opens up insights into the production of N/P co-doped carbon materials for supercapacitor applications.