Fallen autumn leaves – The source of highly porous carbon for Zn-ion hybrid supercapacitors

Over the years, many sophisticated synthetic two-dimensional (2D) carbon materials have become increasingly popular for supercapacitors, e.g. zinc-ion hybrid supercapacitors (ZHSC) due to their ordered structure and high energy density. Additionally, ZHSC is a very demanding device, where finding efficient materials is challenging and the energy storage mechanism remains unclear. Biomass-derived carbon materials exhibit many drawbacks due to their impurities and defective structure, low stability and poor capacitance. In this study, a ZHSC was assembled via carbonization and activation of leaves collected from city streets and utilized as a cathode material. The AC650_Zn-foil presented a high specific capacitance of 95 F·g-1 and a high energy density of 86 W·h·kg−1 at 210 W·kg−1. Furthermore, a superior power density of 40,960 W·kg−1 at 33 W·h·g−1 was presented compared to other investigated materials. In addition, we identified the processes that occurred in the following device, which demonstrated a mechanism that determines the migration of Zn ions, as well as the chemical reactions involved in Zn ions.