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.