Abstract:
In this study, we report the fabrication and performance evaluation of an eco-friendly, low-
cost supercapacitor in which coconut shell charcoal serves as the active carbon material
blended with cement to create the electrode. Coconut shell charcoal is readily available,
renewable, and microporous, and was produced via controlled low-oxygen combustion. This
carbon–cement supercapacitor material could revolutionize multifunctional infrastructure
such as residential energy storage, self-charging roads, remote/off-grid shelters, wind
turbines, and tidal power systems. The finely milled activated charcoal was mixed with
ordinary Portland cement at various weight ratios. The carbon black (CB) was prepared from
cleaned coconut shells that were crushed and sieved to a 0.1 mm particle size prior to
carbonization at 550 °C inside a box furnace. Then, CB was chemically activated with
potassium hydroxide (KOH) in a 1:2 weight ratio of CB: KOH. CB ratio used as 12, 14, 16%
and 18% cast into thin electrodes (~2 mm thick), followed by standard curing and drying.
Electrochemical testing was conducted in a symmetric cell using aqueous electrolytes of 1
M KCl. Cyclic voltammetry exhibited quasi-rectangular profiles indicative of electric
double-layer capacitance behaviour, and increasing the ratio of CB in cement-based
supercapacitors enhances their electrochemical performance. As the CB content rises, the
areal capacitance improves, attributed to the increased surface area and conductivity
provided by the carbon network. The specific capacitance varied from 42 to 191.7 μF/g, and
the areal capacitance 1.52 to 6.65 μF/cm2, obtained in the electrode sample containing 12 to
18% content of CB. These findings illustrate how agricultural waste (burnt coconut shell)
can be upcycled into a functional carbon-cement electrode, potentially enabling scalable,
structurally embedded energy storage solutions for infrastructure.
