Boron and nitrogen co-doped porous carbon for supercapacitors: A comparison between a microwave-assisted and a conventional hydrothermal process

Abstract

Abstract An ultrafast synthesis method is proposed for a boron and nitrogen co-doped porous carbon using biomass material as a precursor through a combination of a microwave-assisted hydrothermal method (MHT) followed by a pyrolysis process. Compared with a conventional hydrothermal carbonization method (HTC), the MHT method exhibits unparalleled advantages, such as a high energy efficiency and a uniform and ultrafast reaction. The pore structure, elemental composition and electrochemical performance of the materials from the two methods were studied and compared. The results showed that when water was used as the solvent, a porous texture with a surface area of 823 m2 g−1 was obtained by the HTC after 24 h; in contrast, a similar surface area of 813 m2 g−1 could be easily obtained in only 20 min with MHT. Furthermore, when boric acid was used as the solvent, MHT-20min-10% presented similar heteroatom (B and N) contents as the HTC sample but with a significantly improved surface area (994 vs. 666 m2 g−1) and specific capacitance (120 vs. 106 F g−1) compared to those of HTC-24h-10%. Therefore, compared with the HTC, MHT is an ultrafast synthesis method and also is the best option to obtain high surface area porous carbon materials doped with B and N heteroatoms with suitable pore size distribution, which are beneficial in electrode materials for supercapacitors.