3.1. Preparation of Coconut Shell-Derived Activated Carbon

Coconut shells were sourced from a local fruit market near Jiujiang University. Initially, these shells were chopped into small fragments and thoroughly cleaned to remove the residual dust. The fragments were then oven-dried at 60 °C for 48 h, after which they were ground into powder. This obtained coconut shell powder was mixed with KOH in a weight ratio of 1:1, and then activated at 800 °C for 2 h under a nitrogen atmosphere, maintaining a heating rate of 2 °C min⁻¹. The resulting mixture was washed with dilute HCl and deionized water until it reached a pH of 7, and then oven-dried overnight at 60 °C to yield the coconut shell-derived activated carbon (denoted as CSAC). For comparison, the coconut shell-derived carbon (abbreviated as CSC) was also prepared without adding KOH, following the same procedure. Figure 8 provides a schematic diagram depicting the CSAC preparation process and its subsequent application in supercapacitors.

Schematic diagram for preparing CSAC and its application in supercapacitors.