Noncorrosive and Nonpolluting Synthesis of Biomass-Derived Nanosheets with B, N Codoping

The green synthesis of biomass multifunction carbon is a major research direction within the carbon field. In this work, double-ion codoped two-dimensional (2D) carbon nanosheets, derived from biomass by recyclable boric acid templates, are prepared as supercapacitor electrode materials. Here, biomacromolecules from pomacea canaliculata egg (an exotic invasive species in China) self-assemble uniformly on the surface of H3BO3 plates by hydrogen bonding, thus forming a precursor with a sandwich structure. Subsequently, gas from the H3BO3 pyrolysis further inflates the resultant carbon material to 2D-shaped ultrathin nanosheets and also to acquire the carbon material (NBC) after simple water-washing. NBC has the following advantages: (1) N, B codoping changes the electron distribution of the carbon lattice, enhancing the electrochemical activity and conductivity; (2) abundant and uniformly distributed active sites are produced on the carbon nanosheet surface due to the full contact between boric acid (as both the template and doping source) and the biomass precursor; (3) the reagent used in this work (H3BO3) can be recycled and used repeatedly without pollution to the environment, achieving the closed-loop usage of chemical reagents. Compared with the traditional alkaline activation method, this work has a better prospect in view of material stability, preparation difficulty, and environmental protection. In terms of performance, the NBC//NBC delivers an energy density of 8.2 Wh kg–1 and a maximum power density of 2500 W kg–1. Besides, NBC//NBC preserves about 92.3% high specific capacitance after 104 cycles, meaning its splendid stability.