Ultrahigh surface area carbon nanosheets derived from lotus leaf with super capacities for capacitive deionization and dye adsorption

Abstract

High surface area, suitable pore size distribution and good wettability of carbonaceous materials are crucial for a variety of surface and interfacial interaction-related applications. Herein, hydrophilic porous carbon nanosheet with an ultrahigh surface area (4482 m2 g−1) was prepared using lotus leaf (LL) as the carbon source. It was revealed that the surface area and microporosity are dependent on the reactivity of the precursor, which can be characterized by the sp2 hybridized carbon and oxygen contents. The LL-derived carbon was used as electrodes in supercapacitors, which exhibited specific capacitances of 225F g−1 and 289F g−1 at 0.5 A g−1 in 1 M NaCl and 6 M KOH electrolytes. The resultant carbon also showed excellent capacitive deionization performance, i.e. electrosorption capacities of 13.5 mg g−1 and 65.0 mg g−1 towards NaCl at 1.2 V and 1.6 V, respectively. Furthermore, the nanosheets displayed an extraordinary adsorption capacity of 4181.2 mg g−1 towards methylene blue, which is the highest for all carbonaceous adsorbents reported so far. The excellent performances are associated with the nanosheet morphology which provides short transportation path, the ultrahigh surface area and the excellent wettability.