In this work, N, S co-doped pomelo peel derived carbon is successfully prepared by a simple one-step method. The derived carbon exhibits high specific capacitance (317 F g(-1)) and excellent rate capability (69.7% of capacitance retention at 15 A g(-1)), owing to its large S-BET, high heteroatom doping rate and suitable graphitization degree (these characteristics are derived from the synergistic activation and reduction of thiourea dopant). The one-step method is applied to the other two biomasses (bamboo fiber and sugarcane bagasse). The derived carbons of the other two biomasses still show outstanding electrochemical performance due to their similar microstructure and chemical composition to pomelo peel derived carbon, which suggests the universality of the one-step method. The series of carbon materials are applied to symmetric supercapacitors, all of which show high energy density (30.6-24.6 Wh kg(-1)), indicating the potential application of such carbon materials in energy storage. (C) 2019 Elsevier Ltd. All rights reserved.