Synthesis and electrochemical performance of high surface area hierarchical porous carbon with ultrahigh mesoporosity for high-performance supercapacitors

Abstract

Hierarchical porous carbons (HPCs) with both high Brunauer–Emmett–Teller (BET) surface area and high mesoporosity have been synthesized by combination of self-template and one-step carbonization–activation strategy. Ferric citrate (FC) was used as the carbon precursor and self-template source, which not only produced a great number of mesopores with size of 5–20 nm but also brought about high content of graphitic structures by catalytic graphitization. The KOH dosage played a significant role in adjusting the BET surface area and pore size distribution. Importantly, considerable mesopores with width of 2–4 nm were created by KOH, owing to which both high BET surface area and high mesoporosity were achieved. The resultant HPCs exhibited high BET surface area (2055 m2 g−1), large pore volume (2.527 cm3 g−1), and ultrahigh mesoporosity (95.1%). As the electrode material for supercapacitors, the HPC presents a high specific capacitance of 289 F g−1 at 0.2 A g−1 and maintains 205 F g−1 at 30 A g−1 with the capacitance retention of 71% in 6 M KOH electrolyte. Additionally, the HPC-based two-electrode supercapacitor with 1 M Na2SO4 solution as electrolyte delivered a high energy density of 18.24 Wh kg−1 at a power density of 499 W kg−1 and retained 11.63 Wh kg−1 at a power density of 15 kW kg−1. The simple process and excellent performances make HPCs quite promising alternative for application of high-performance supercapacitors in the next generation.