Enhancement of gelatinization on electrochemical performance of corn starch-based porous carbon as electrode material in supercapacitors

Abstract

Biomass-based porous carbon is extensively utilized as an electrode material for double-layer supercapacitors due to its cost effectiveness and wide availability. However, it is still a challenge to construct reasonable pore structures to prepare biomass porous carbon materials with excellent electrochemical properties. In this work, corn starch was chosen as carbon source to prepare porous carbon materials through gelatinization, pre-carbonization and activation. The impact of gelatinization temperature on the pore structure and electrochemical properties of carbon materials was thoroughly investigated. With the increase of gelatinization temperature, the small mesoporous ratio in the carbon materials firstly increases and then decreases, which is positively correlated to the changes of specific capacitance. Among all samples tested, the corn starch-based porous carbon (SAC-85-R6A7) prepared by gelatinizing at 85 °C followed by pre-carbonizing at 600 °C and activating at 700 °C exhibits exceptional electrochemical characteristics with a specific capacitance up to 386.43 F g−1 at 0.5 A g−1 and a retention rate of 75.81 % even at 20 A g−1. Due to its wide voltage window range from 0 to 1.1 V, the two-electrode device for SAC-85-R6A7//SAC-85-R6A7 shows an outstanding energy density of 12.94 Wh kg−1 at a power density of 277.33 W kg−1 and still retains an energy density value as substantial as 10.75 Wh kg−1 even though at 6.45 kW kg−1, and presents a capacity retention of 95.33 % after 10,000 cycles at 5 A g−1, the coulomb efficiency close to 100 %. The change of gelatinization temperature optimizes the pore size structure of the carbon material, further promotes the rapid penetration of electrolyte ions, and improves the electrochemical performance.