Pore size expansion of chitosan derived porous carbon for H2SO4 electrolyte based supercapacitor

•The micropores in chitosan-based carbon (PC-C) are available to KOH electrolyte.•PC-C is not suitable for H2SO4 electrolyte due to its small pore size.•Trimesic acid is introduced as a carbon precursor to tune the porous structure.•The modified carbon (PC-CT) shows expanded pore size and mesopres.•Compared with PC-C, PC-CT exhibits high-rate performance in H2SO4 electrolyte. Microporous carbon (PC-C) was prepared using chitosan and ZnCl2 as carbon precursor and activating agent, respectively. Electrochemical measurements and material characterization show that the microporous nature of PC-C limits the ion transfer in H2SO4 electrolyte, resulting in a lower specific capacitance and rate performance in H2SO4 electrolyte compared with KOH electrolyte. Trimesic acid was introduced into the carbon precursor to regulate the porous structure by generating more meso- and macropores, which facilitate the transmission of electrolyte ions with bigger ionic size. In this case, the specific capacitance of the modified carbon can reach up to 180 from 84.6 F g−1 in H2SO4 electrolyte. The assembled supercapacitor cell in H2SO4 electrolyte can deliver an energy density of 4.9 Wh kg−1 at a high-power density of 2500 W kg−1, which is much higher than that (0.4 Wh kg−1) of PC-C. Our study provides a guidance for the preparation and regulation of porous carbon suitable for different aqueous electrolytes.