The performance of activated carbon as electrode material in supercapacitor devices obtained from walnut shells has been enhanced by incorporating a fine dispersion of ultrasmall MnO clusters synthesized towards a novel colloidal route. The resulting MnO@WAC composite material outperforms the raw carbon in electric conductivity and volumetric capacitance, making it an excellent electrode for practical supercapacitor applications.

Abstract

Activated carbon (AC) materials from renewable sources are widely used in electrochemical applications due to their well-known high surface area. However, their application as electrode material in double-layer electrochemical devices may be limited due to their relatively low electrical conductivity and lightweight. To overcome these limitations, the incorporation of pseudocapacitance metal oxide nanoparticles is an optimum approach. These nanoparticles can provide a second energy storage mechanism to the composite, mitigating the loss of surface area associated with their incorporation. As a result, the composite material is endowed with increased conductivity and higher density, making it more suitable for practical implementation in real devices. In this study, we have incorporated a fine dispersion of 1 % of MnO clusters into a highly porous activated carbon synthesized from walnut shells (WAC). The high-resolution electron microscopy studies, combined with their related analytical techniques, allow us to determine the presence of the cluster within the matrix carbon precisely. The resulting MnO@WAC composite demonstrated significantly improved capacitive behavior compared with the WAC material, with increased volumetric capacitance and higher charge retention at higher current densities. The composite‘s electrochemical performance suggests its potential as a promising electrode material for supercapacitors, addressing drawbacks associated with traditional AC materials.