Browsing by Author "Genel, Lyas"

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Green Synthesis of Hierarchical Nitrogen-Doped Porous Activated Carbon Material Based on Biomass Waste for High-Performance Energy Storage as Supercapacitor
(Pergamon-elsevier Science Ltd, 2025) Genel, Lyas; Yardim, Yavuz; Saka, Cafer
Superior electrochemical capacitance properties can be achieved with biomass-based carbon materials synthesized with appropriate activation methods. In this study, chestnut shells were employed as a biomass-derived carbon precursor for the development of high-performance electrode materials for electrochemical energy storage applications. The chestnut shells were first pyrolyzed through chemical activation with sodium hydroxide to produce N-doped NaOH-CS. Then, the surface properties were further improved by nitrogen (N) atom doping to the AC sample using ammonia. Due to the favorable pore structure, specific surface area, and N content, the N-doped NaOH-CS supercapacitor material exhibits excellent capacitive performance of 625 F/g at 1 A/g, representing a 500 % increase compared to the NaOH-CS material. Different analytical methods are used for the characterisation of the materials. Experimental results confirm that the N-doped NaOH-CS supercapacitor material shows a stability of 84.6 % over 5000 consecutive cycles. At a current density of 1 A/g, the NaOH-CSGCE//AC material delivers an energy density of 21.2 Wh/kg with a power density of 558 W/kg. When the current density increases to 8 A/g, it maintains a comparable energy density of 22.0 Wh/kg while achieving a significantly higher power density of 4400 W/kg. These findings demonstrate the suitability of biomass waste obtained from chestnut shells for high-performance electrode materials.
Sustainable Conversion of Biomass Waste Into CdO@S-Doped Carbon for High-Performance Energy Storage
(Pergamon-Elsevier Science Ltd, 2026) Saka, Cafer; Yardim, Yavuz; Genel, Lyas
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.