Facile Synthesis of Hierarchically Porous N/P Codoped Carbon with Simultaneously High-Level Heteroatom-Doping and Moderate Porosity for High-Performance Supercapacitor Electrodes

Multiple heteroatom doping represents an effective strategy for improving the supercapacitive performance of carbon electrodes due to its combined merits of pseudocapacitance and double layer capacitance. However, a green and efficient approach for generating heteroatoms codoped carbons which simultaneously possess high-level heteroatom-doping and moderate porosity remains a big challenge. Here, we put forward a CaCO3-assistant technique for the fabrication of nitrogen/phosphorus codoped hierarchical porous carbons (NPHCs). The as-prepared 1NPHC-850 integrates the structural characteristics of high-level heteroatom-doping (8.72 at. % for N, 4.44 at. % for P, and 10.24 at. % for O), large surface area (up to 414 m2 g–1), and triple micromeso-macro pore structure. It exhibits a high specific capacitance of 212 F g–1 at 0.5 A g–1 and an excellent rate performance with a capacitance ratio of 75% at 20 A g–1. Moreover, the 1NPHC-850-based symmetrical supercapacitor device could achieve a high energy density of 10.61 Wh kg–1 in aqueous electrolyte and an ultralong cycling life (capacitance retention of 86.3% after 10,000 cycles). Our work not only offers a facile strategy to produce advanced multiple heteroatom-doped carbon materials but also provides reference for rational regulation of chemical composition and pore structure in pursuit of better carbon electrodes for supercapacitors.