Molten salt and air induced nitrogen-containing graphitic hierarchical porous biocarbon nanosheets derived from kitchen waste hydrolysis residue for energy storage

Abstract

Herein, the feasibility to fabricate nitrogen-containing biocarbon material from kitchen waste hydrolysis residue by a molten salt-air -assisted synthetic strategy is investigated. Hierarchical porosity and graphitic carbon nanosheet structure are found for the developed biocarbon. The porosity is mainly induced by O2 and the specific surface area of biocarbon (fabricated in air) reaches 818.65 m2 g−1, much higher than that of O2-free sample (11.84 m2 g−1). Meanwhile, the heteroatom (e.g. N) is also retained and introduced into carbon structure even in air atmosphere. It is also suggested that O2 may accelerate a destructive effect on the order of graphitic structure, while the molten salts of NaCl and KCl play the roles of graphitization catalyst and sealing agent, promoting the graphitization of biocarbon. When the developed biocarbon is applied as electrode material, the as-assembled symmetric supercapacitor exhibits a high energy density of 11.7 Wh kg−1 in 1 M Na2SO4. Forthermore, the applicability of current strategy for industrial biocarbon fabrication is verified by salt recycling test and ten times scale-up trail experiment, which shows great potential for green and large-scale production of advanced carbon materials from biomass precursors, for exmple, kitchen waste hydrolysis residue.