Hierarchical Micro-/Mesoporous Carbon Derived from Rice Husk by Hydrothermal Pre-Treatment for High Performance Supercapacitor

The exploration of highly abundant and available biomass wastes as sustainable precursors through a scalable and cost-effective synthesis strategy is extremely important for novel materials development in energy storage and conversion technologies. Herein, we have successfully fabricated hierarchical micro-/mesoporous carbons (HMMC) from low-cost and eco-friendly agricultural residues via an easy method. The highly hierarchical porous carbons were obtained from rice husk via NaOH-assisted hydrothermal pre-treatment followed by carbonization/activation process. The NaOH-assisted hydrothermal treatment removed ash content and facilitated the development of pores, especially the mesopores, resulting in hierarchical porous carbons with high specific surface area, large pore volume and high ratio (49.3%) of mesopores. These hierarchically structural advantages guarantee the excellent performances of the resultant porous carbons as electrodes for supercapacitors. The rice husk-derived HMMC electrode exhibit a maximum capacitance of 302.2 F g(-1) at a current density of 1 A g(-1 )in a three-electrode system with 6 M KOH as electrolyte, which is significantly better than 193.7 F g(-1) at 1 A g(-1) obtained on rice husk-derived microporous carbons via direct carbonization and activation. Moreover, the NaOH-assisted HMMC electrodes also show good cycle stability. These results demonstrated that NaOH-assisted hydrothermal pre-treatment is a facile and effective way to produce hierarchical porous carbons from natural biomass wastes with improved electrochemical performances for supercapacitors. (C) 2018 The Electrochemical Society.