Properties of Porous Carbon Derived from Cornstalk Core in High‐Performance Electrochemical Capacitors

Cornstalk core, a renewable by-product of agriculture, has been used as a carbon precursor to prepare high-performance electrode materials used in electrochemical capacitors (ECs). The influences of temperature and the ratio of activator (KOH) to carbon (mKOH/mC) on the structures of porous carbon materials (PCMs) derived from cornstalk core have been investigated systematically. The PCM obtained at optimal conditions (mKOH/mC=6, activated at 800 °C) exhibits a porous structure with a large specific surface area of 2139 m2 g−1 and total pore volume of 1.16 cm3 g−1. Acting as an electrode material, the optimum PCM exhibits excellent capacitive performance with a specific capacitance of 317.0 F g−1 at a scan rate of 1 mV s−1. More promising, a high power density of 28.3 kW kg−1 and energy density of 6.8 Wh kg−1 are achieved in 6 mol L−1 KOH aqueous electrolyte, as well as high-rate capability and excellent cycling stability. The capacitor has a time constant of about 0.3 s, and could retain more than 93 % of its initial capacitance after 10 000 cyclic processes. This work proposes a potential biomass resource to produce effective porous carbons for high-performance ECs.