Molten-salt-templated fabrication of N, S co-doped hierarchically porous carbons for high-performance supercapacitors

Heteroatom-doped porous carbons with hierarchical structures have been regarded as promising electrode materials for high-performance supercapacitors. Herein N, S co-doped hierarchically porous carbon (NSHPC) was synthesized by a molten-salt templated method using eutectic KCl/LiCl as the template, chitosan as the carbon/nitrogen source, and K2SO4 as the sulfur source, respectively. The as-prepared NSHPC exhibits a large specific surface area of 994.2 m2 g−1 with hierarchical pores of 1.6, 2.5, and 3.7 nm in diameter, as well as high heteroatom content with 4.5% of N and 10.2% of S elements. Consequently, the NSHPC electrode delivers high specific capacitances of 277 F g−1 at a scan rate of 25 mV s−1, and 195 F g−1 at a current density of 10 A g−1, and also retains a 48.9% retention when the current density is increased to 50 A g−1. Moreover, the electrode also remains 87.4% of initial capacitance after submitting 5000 charge/discharge cycles at 10 A g−1.