Green nanotechnology is now emerging to address society's global sustainability issues by recycling numerous industrial and bio-wastes to produce functional carbonaceous nanomaterials like biochar, 2D graphene, graphene oxide, carbon nanotube (CNT), activated carbon (AC), etc. In this study, we have synthesized AC via the hydrothermal decomposition approach of the walnut shell under high temperature and pressure in a hydrothermal autoclave at temperature ranges from 200 to 250 ℃. The synthesized AC has a high specific surface area of 408.8 m2/g. It has an excellent specific capacitance of 204F/g at 1 A/g of current density with good cyclability up to 10,000 cycles.
