Preparation of porous nitrogen-doped activated carbon derived from rice straw for high-performance supercapacitor application

Abstract

Environmental-friendly and low-cost biomass-derived materials have been attracted many attentions to produce porous activated carbon (AC) with high surface area for supercapacitor (SC) application. In this study, rice straw (RS), an agricultural waste, is used to prepare ACs with a two-step process of carbonization and KOH activation. As-produced AC has a high specific surface area (SSA) of 2651 m2g-1 with hierarchical pore structure. In order to enhance the performance of SC, nitrogen-doping strategy is carried out to increase nitrogen functional groups in the AC using melamine as a precursor. The SSA of the nitrogen-doped AC is 2537 m2g-1 and the capacitance of 324 F/g is achieved using nitrogen-doped AC at a current density of 0.5 Ag-1 in 6 M KOH aqueous electrolyte. The capacitance retention is 95% after 10,000 charge and discharge cycles at a current density of 5.0 Ag-1. In addition, ionic liquid is employed as the electrolyte for the supercapacitor. The energy density of 48.9 Wh/kg at a power density of 750 W/kg can be achieved using EMI-TFSI electrolyte. We think that the proposed method can be used for a variety of biomass for preparation of ACs with high specific surface area and nitrogen functional groups for the energy storage applications.