Mass production of hierarchically porous carbon nanosheets by carbonizing ‘‘real-world” mixed waste plastics toward excellent-performance supercapacitors Yanliang Wen a,b , Krzysztof Kierzek c , Xuecheng Chen a,b,⇑ , Jiang Gong d,⇑ , Jie Liu b , Ran Niu e , Ewa Mijowska a , Tao Tang b,⇑ a Nanomaterials Physicochemistry Department, Faculty of Chemical Technology and Engineering, West Pomeranian University of Technology, Szczecin, Piastów Ave. 42, 71-065 Szczecin, Poland b State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, China c Faculty of Chemistry, Department of Polymer and Carbonaceous Materials, Wroclaw University of Technology, Wroclaw, Poland d Key Laboratory for Material Chemistry of Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China e Department of Physics, Cornell University, Ithaca, NY 14853, USA article info Article history: Received 25 November 2018 Revised 4 March 2019 Accepted 5 March 2019 Keywords: Waste plastic Carbonization Carbon nanosheet Hierarchical pore Supercapacitor abstract Recently, sustainable development and serious energy crisis called for appropriate managements for the large number of municipal and industrial waste plastics as well as the development of low-cost, advanced materials for energy storage. However, the complexity of waste plastics significantly hampers the appli- cation of ever used methods, and little attention is paid to the utilization of waste plastics-derived carbon in energy storage. Herein, porous carbon nanosheets (PCNSs) was produced by catalytic carbonization of ‘‘real-world” mixed waste plastics on organically-modified montmorillonite (OMMT) and the subsequent KOH activation. PCNSs was featured on hierarchically micro-/mesoporous structures with the pore size distribution centered on 0.57, 1.42 and 3.63 nm and partially exfoliated graphitic layers, and showed a high specific surface area of 2198 m 2 g À1 and a large pore volume of 3.026 cm 3 g À1 . Benefiting from these extraordinary properties, PCNSs displayed a superior performance for supercapacitors with high specific capacitances approaching 207 and 120 F g À1 at a current density of 0.2 A g À1 in aqueous and organic elec- trolytes, respectively. Importantly, when the current density increased to 10 A g À1 , the specific capaci- tances remained at 150 F g À1 (72.5%) and 95 F g À1 (79.2%) in aqueous and organic electrolytes, respectively. The outstanding rate capability of PCNSs was in sharp contrast to the performance of tradi- tional activated carbons. This work not only provides a potential way to recycle mixed waste plastics, but also puts forward a facile sustainable approach for the large-scale production of PCNSs as a promising candidate for supercapacitors. Ó 2019 Elsevier Ltd. All rights reserved. 1. Introduction The world production of plastics rapidly increased from 1.7 mil- lion tons in 1950 to 355 million tons in 2016 (PlasticsEurope, 2017). Most plastics are not biodegradable and originate from the unsustainable fossil fuels. The ever-increasing generation of waste plastics has created terrible environmental problems and aggravated the energy crisis. Sustaining development and the growing global demand for energy and materials have promoted to develop low environmental impact technologies for the utiliza- tion of waste plastics (Arena, 2012; Ignatyev et al., 2014; Zhao et al., 2010b) and to explore sustainable approaches for producing materials with high performances in the energy conversion and storage (Chen et al., 2013; Titirici and Antonietti, 2010). Mechani- cal recycling of waste plastics is far from being widely accepted because of the low quality of the recycled plastic mixture. Chemi- cal recycling recovers the petrochemical components of waste plastics to produce monomers, fuels, and other useful chemicals (Keane, 2009; Serrano et al., 2012). The main chemical valorization processes of waste plastics are summarized as four types: steam https://doi.org/10.1016/j.wasman.2019.03.006 0956-053X/Ó 2019 Elsevier Ltd. All rights reserved. ⇑ Corresponding authors at: Key Laboratory for Material Chemistry of Energy Conversion and Storage, Ministry of Education, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, No. 1037, Luoyu Road, Wuhan 430074, PR China (J. Gong). E-mail addresses: xchen@ciac.ac.cn (X. Chen), gongjiang@hust.edu.cn (J. Gong), ttang@ciac.ac.cn (T. Tang). Waste Management 87 (2019) 691–700 Contents lists available at ScienceDirect Waste Management journal homepage: www.elsevier.com/locate/wasman