Cellulose-based aerogel derived N, B-co-doped porous biochar for high-performance CO₂ capture and supercapacitor

The remarkable characteristics of porous biochar have generated significant interest in various fields, such as CO₂ capture and supercapacitors. The modification of aerogel-derived porous biochar through activation and heteroatomic doping can effectively enhance CO₂ adsorption and improve supercapacitor performance. In this study, a novel N, B-co-doped porous biochar (NBCPB) was synthesized by carbonating and activating the N, B dual-doped cellulose aerogel. N and B atoms were doped in-situ using a modified alkali-urea method. The potassium citrate was served as both an activator and a salt template to facilitate the formation of a well-developed nanostructure. The optimized NBCPB-650-1 (where 650 corresponded to activation temperature and 1 represented mass ratio of potassium citrate activator to carbonized NBCPB-400 precursor) displayed the largest micropore volume of 0.40 cm³·g^-1 and a high specific surface area of 891 m²·g^-1, which contributed to an excellent CO₂ adsorption capacity of 4.19 mmol·g^-1 at 100 kPa and 25 °C, a high CO₂/N₂ selectivity, and exceptional reusability (retained >97.5 % after 10 adsorption-desorption cycles). Additionally, the NBCPB-650-1 electrode also delivered a high capacitance of 220.9 F·g^-1 at 1 A·g^-1. Notably, the symmetrical NBCPB-650-1 supercapacitor exhibited a high energy density of 9 Wh·kg^-1 at the power density of 100 W·kg^-1. This study not only presents the potential application of NBCPB-650-1 material in CO₂ capture and electrochemical energy storage, but also offers a new insight into easy-to-scale production of heteroatomic-modified porous biochar.