Nitrogen-Doped Porous Carbon Derived from Cellulose Microfibers of Rice Straw for High-Performance Electrodes of Supercapacitors

Biomasses are promising precursors of porous carbons. However, the complexity in composition and microstructure of biomasses might result in poor quality reproducibility of biomass-derived porous carbons. It is essential to develop reliable approaches to prepare biomass-derived porous carbons. In this work, a nitrogen-doped porous carbon derived from cellulose microfibers of rice straw was prepared. The cellulose microfibers were first extracted from rice straw by alkali treatment. Then, a hydrochar was fabricated by hydrothermal treatment of the cellulose microfibers. Nitrogen-doped porous carbon was finally obtained by calcination under high temperature with K2CO3 and CO(NH2)2 as the activating agent and nitrogen dopant, respectively. The prepared carbon material has an ultrahigh specific surface area (∼2800 m2/g) and a moderate nitrogen doping (1.65 atom %). Consequently, rice-straw-derived porous carbon achieves a remarkable specific capacitance (380.1 F/g at 0.5 A/g) and a good rate capability (61.8% capacitance retention at 50 A/g). In addition, the porous carbon exhibits good cycling stability. The loss of capacitance is only 4.6% after 10 000 charge–discharge cycles. This study provides a robust method for the preparation of porous carbons from lignocellulosic biomasses.