Preoxidation Assisted Alkali Activation Constructs Polyacrylonitrile-Based Porous Carbon for Supercapacitors

The porous structural tailoring of polyacrylonitrile-based carbon materials is the key to maximize capacitive performance. Herein, hierarchical porous carbons (HPC) with high specific surface area and controllable porosity are synthesized by preoxidation assisted alkali activation strategy using polyacrylonitrile as the precursor. The results show that high preoxidation temperature is beneficial to increase the specific surface area and pore volume of HPC. The optimized HPC-300 has a high BET specific surface area of 3161 m² g^-1, a micropore volume of 1.45 cm³ g^-1, and an A_D/A_G of 3.56. Electrochemical test shows that the specific capacitances of HPC-300 in 6 M KOH electrolyte at 1 A g^-1 and 10 A g^-1 are 314.1 F g^-1 and 213.0 F g^-1, respectively, with a capacitance retention of 67.8 %. The assembled supercapacitors based on HPC-300 deliver an energy density of 11.7 Wh kg^-1 at a power density of 250.0 W kg^-1 in KOH electrolyte and 21.1 Wh kg^-1 at 450.0 W kg^-1 in Na₂SO₄ electrolyte and possess a capacitance retention of 98.1 % over 20,000 charge-discharge cycles. This preoxidation coupled activation method provides a potential strategy for the preparation of PAN-based porous carbon with high specific surface area and capacitance.