Sustainable conversion of biomass waste into CdO@S-Doped carbon for high-performance energy storage

Abstract

In this study, a high-performance and sustainable electrode material was developed from acacia tree bark through a dual-doping strategy involving cadmium oxide (CdO) and sulfur to enhance supercapacitive performance. The biomass precursor was first activated with potassium hydroxide to produce porous activated carbon (ABAC), followed by hydrothermal sulfur doping using sulfuric acid to obtain S-doped ABAC with an enlarged surface area and optimized pore architecture. Subsequently, CdO nanoparticles were uniformly anchored onto the sulfur-doped carbon framework, forming CdO@S-doped ABAC with superior electrical conductivity and abundant redox-active sites. Structural and surface analyses, including XRD, FTIR, SEM, TEM, BET, and XPS, confirmed the successful incorporation of CdO and sulfur species, resulting in a hierarchically porous structure with enhanced surface functionalities. Electrochemical characterization via cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy revealed a substantial improvement in capacitive behavior. Specifically, S-doped ABAC and CdO@S-doped ABAC exhibited approximately fourfold and fivefold higher specific capacitance, respectively, compared to pristine ABAC. Moreover, the CdO@S-doped ABAC electrode retained 93.6 % of its initial capacitance after prolonged cycling, demonstrating outstanding electrochemical stability. The remarkable enhancement in energy storage performance is attributed to the synergistic interaction between CdO nanoparticles and sulfur dopants, which facilitates efficient charge transport and faradaic activity. These findings highlight the potential of biomass-derived, co-doped carbon materials as environmentally friendly and efficient electrodes for next-generation supercapacitors.