Pore structure regulation of hierarchical porous agaric-derived carbon via boric acid activation for supercapacitors

The development of sustainable carbon materials from biomass for electric double-layer supercapacitors is a promising solution to alleviate energy and environmental pressures. The electrochemical performance of biomass-derived carbon materials is greatly affected by their hierarchical porous structure. In general, the pore structure of biomass-derived carbon activated using chemical method is dominated by micropores with few mesopores. This hinders the transmission of electrolyte ions, thus limiting the electrochemical properties. Here we have designed a green unique boric acid-assisted method to synthesize hierarchical porous agaric-derived carbon. Benefiting from the unique hygroscopic recovery characteristics of agaric, boric acid can enter the interior of the agaric and act as a novel activator to effectively adjust the pore structure of porous carbon. During the carbonization process, the melted boron oxide with high viscosity and excellent wetting properties adheres to the agaric matrix as a template, which plays a key factor for increasing the mesopores (<4 nm) and promoting ions transport. The synthesized porous carbon has a high specific surface area (2279.5 cm2 g−1), more reasonable hierarchical porous structure, abundant nitrogen atom doping (4.69 at.%) and high capacitance (502 F g−1 @ 0.5 A g−1). The symmetric supercapacitor tested in 1 M Na2SO4 electrolyte has excellent performances. This optimization strategy provides a new idea to design more reasonable hierarchical porous biomass-derived carbon materials.