Preparation of starch-derived porous carbon with improved yield by autogenic pressure carbonization and KOH activation for high-performance supercapacitor

The preparation of carbon materials from biomass for energy storage is a sustainable approach to mitigate the issues of fossil fuel shortage and climate change. Starch is a desirable precursor for the preparation of carbon material due to its high carbon content, renewability, and low cost. However, the pyrolysis of starch produces a high yield of volatile products and low yield of carbon, which hinder its application. In this study, a sustainable method was developed to improve the carbon yield of starch and develop hierarchical porosity. Autogenic pressure carbonization produced additional deposit carbon besides the residual carbon. The carbon yield was improved to 32%, which is about 3 times of that through direct pyrolysis. The subsequent KOH activation developed hierarchical porosity and abundant functional groups. A high specific surface area of 3182 m 2 g −1 with meso-/macropore proportion of 0.33 was achieved. The outstanding properties facilitate the electrochemical performances of carbon hybrids. Applied in supercapacitors, the carbon hybrids exhibited remarkable capacitance (316 F g −1 at 1 A g −1 ), rate performance (86% retention at 20 A g −1 ), and cycling stability (92.5% retention after 10000 times cycles) in the electrolyte of 6 M KOH. Graphical Abstract