B,N-Codoped Porous C with Controllable N Species as an Electrode Material for Supercapacitors

Manufacturing heteroatom-doped porous C with controllable N species is an important issue for supercapacitors. Herein, we report a low-cost and simplified strategy for synthesizing B,N-codoped porous C (BNPC) by a freeze-drying chitosan–boric acid aerogel beads and subsequent carbonization treatment. The BNPC samples were studied using various characterization technologies. The introduction of boric acid to chitosan successfully induced the formation of B,N-codoped C with a well-developed 3D interconnected porous structure. The B doping had a significant impact on the distribution of N species in the samples. Moreover, the good wettability of the sample resulting from B doping is favorable for electrolyte diffusion and ion transport. As a consequence, the optimal BNPC sample showed an excellent specific capacitance of 240 F g–1 at 0.5 A g–1 and an outstanding capacitance retention of 95.1% after 10000 cycles at 5 A g–1. An assembled symmetrical supercapacitor displayed an energy density of 11.4 Wh kg–1 at a power density of 250 W kg–1. The proposed work provides a simple and effective method to obtain B,N-codoped C-based materials with high electrochemical performance.