Carbon framework modification; an interesting strategy to improve the energy storage and dye adsorption

Abstract

Porous carbons find various applications, including as adsorbents for clean water production and as electrode materials in energy storage devices such as supercapacitors. While supercapacitors reach higher power densities than batteries, they are less widely used, as their energy density is lower. We present a low-temperature wet ultrasonochemical synthesis technique to modify the surface of activated carbon with 1 wt% Cu nanoparticles. We analyzed the modified carbon using X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy and confirmed the composite formation by N₂ adsorption–desorption isotherms at 77 K. For comparison, we did the same tests on pristine carbon. We used the modified carbon as an electrode material in a home-built supercapacitor filled with gel polymer electrolyte and as an absorbent of Malachite green dye. In both applications, the modified carbon performed substantially better than its pristine counterpart. The modified-carbon supercapacitor exhibited a single electrode-specific capacitance of approximately 68.9 F g⁻¹. It also demonstrated an energy density of 9.8 W h kg⁻¹ and a power density of 1.4 kW kg⁻¹. These values represent improvements over the pristine-carbon supercapacitor, with increases of 25.7 F g⁻¹ in capacitance, 3.8 W h kg⁻¹ in energy density, and 0.5 kW kg⁻¹ in power density. After 10 000 charging–discharging cycles, the capacitance of the modified-carbon supercapacitor decreased by approximately 10%, indicating good durability of the material. We found that the modified carbon's absorbance capacity for Malachite dye is more than that of the pristine carbon; the adsorption capacity value was ∼153.16 mg g⁻¹ for modified carbon with pseudo-second kinetic order, in accordance with the Redlich–Peterson adsorption model.