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

Abstract

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.