Preparation of High-Performance Porous Carbon Materials by Citric Acid-Assisted Hydrothermal Carbonization of Bamboo and Their Application in Electrode Materials

Renewable energy needs an environmentally friendly and efficient energy storage device. In this work, porous carbon materials with different properties are prepared by citric acid (CA)-assisted hydrothermal carbonization of bamboo and KOH activation. The effects of the ratio of the added CA on the structure of hydrochar and the porous carbon product are studied systematically. It is found that the added CA can improve the carbonization degree of the hydrochar, content of oxygencontaining functional groups, and specific surface area of the final product. The highest specific surface area (3132 m2 g-1) is achieved when 4 g of CA is added (C-HBC-4), which is significantly improved compared to the conventional hydrothermal process. In a three-electrode system, the specific capacitance of C-HBC-4 can reach 435.5 F g-1 at 0.5 A g-1, which is higher than most other bamboo-derived porous carbon materials previously reported. After 30,000 charge and discharge cycles under a current density of 10 A g-1, a retention rate of 97% is achieved. The results in this work show a green and viable path for the preparation of high-performance electrode materials for supercapacitors from biomass.