Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Tunable porous structure of carbon nanosheets derived from puffed rice for high energy density supercapacitors Jianhua Hou a,b,* , Kun Jiang b , Muhammad Tahir c,d , Xiaoge Wu a , Faryal Idrees c,e , Ming Shen b , Chuanbao Cao c,** a Jiangsu Key Laboratory of Environmental Material and Engineering, School of Environmental Science and Engineering, Yangzhou University, Yangzhou, 225000, PR China b School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou, 225000, PR China c School of Material Science and Engineering, Beijing Institute of Technology, Beijing, PR China d Department of Physics, The University of Lahore, Lahore, Pakistan e Institut für Technische Chemie, Post-Doc Fellow, Gottfried Wilhelm Leibniz Universitat Hannover, Callinstr. 3, 30167 Hannover, Germany HIGHLIGHTS • Rice derived, tunable micro/meso- pores structures of carbon nanosheets. • Honeycomb-like architecture is in- duced by ‘puffing effect’. • The “puffing effect” avoiding organic solution usage, leading to green route. • Ultrahigh S BET of 3326 m 2 g -1 with optimized mesopores. • Highest supercapacitors performance of 104 Wh kg -1 or 53 Wh L -1 . GRAPHICAL ABSTRACT ARTICLE INFO Keywords: Porous carbon Biomass Nanosheets Sub-nanopores Mesopores Supercapacitors ABSTRACT The development of green and clean synthetic techniques to overcome energy requirements have motivated the researchers for the utilization of sustainable biomass. Driven by this desire we choose rice as starting materials source. After the explosion effect, the precursor is converted into puffed rice with a honeycomb-like structures composed of thin sheets. These honeycomb-like macrostructures, effectively prevent the cross-linking tendency towards the adjacent nanosheets during activation process. Furthermore, tuneable micro/mesoporous structures with ultrahigh specific surface areas (S BET ) are successfully designed by KOH activation. The highest S BET of 3326 m 2 g -1 with optimized proportion of small-mesopores is achieved at 850 °C. The rice-derived porous N- doped carbon nanosheets (NCS-850) are used as the active electrode materials for supercapacitors. It exhibites high specific capacitance specifically of 218 F g -1 at 80 A g -1 in 6 M KOH and a high-energy density of 104 Wh kg -1 (53 Wh L -1 ) in the ionic liquid electrolytes. These are the highest values among the reported biomass-derived carbon materials for the best of our knowledge. The present work demonstrates that the combination of “puffing effect” and common chemical activation can turn natural products such as rice into functional products with prospective applications in high-performance energy storage devices. http://dx.doi.org/10.1016/j.jpowsour.2017.10.045 Received 27 July 2017; Received in revised form 16 September 2017; Accepted 15 October 2017 * Corresponding author. Jiangsu Key Laboratory of Environmental Material and Engineering, School of Environmental Science and Engineering, Yangzhou University, Yangzhou, 225000, PR China. ** Corresponding author. E-mail addresses: jhhou@yzu.edu.cn (J. Hou), cbcao@bit.edu.cn (C. Cao). Journal of Power Sources 371 (2017) 148–155 0378-7753/ © 2017 Elsevier B.V. All rights reserved. MARK