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    Comparative activation of pine pollen-derived carbon with KOH and CuCl2 for high-performance supercapacitor electrodes
    (Springer Heidelberg, 2025) Atalay, Funda Ersoy; Kaya, Harun; Korkmaz, Aydan Aksogan; Gokturk, Gunay; Guler, Seher
    Biomass-derived porous carbons have emerged as promising candidates for high-performance supercapacitor electrodes owing to their low cost, sustainability, and tunable physicochemical properties. In this work, pine pollen, an abundant and underutilized natural precursor, was converted into porous carbon via hydrothermal carbonization followed by chemical activation using KOH and CuCl2. A systematic comparison of these activation agents was conducted to elucidate their effects on structural, morphological, and electrochemical characteristics. KOH activation produced carbon with a high specific surface area of 2030.32 m2/g and a specific capacitance of 230 F/g at 5 A/g, while CuCl2 activation yielded carbon with a surface area of 736.8 m2/g and a capacitance of 176 F/g. After 5000 charge-discharge cycles, capacitance retention was 76% for the KOH-activated electrode and 93% for the CuCl2-activated counterpart. This study provides the first comprehensive insight into the role of activation chemistry in tailoring pine pollen-derived carbon for supercapacitor applications, demonstrating the potential of pine pollen as a sustainable and low-cost resource for advanced energy storage systems.
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    Electrode material development from natural specularite ore for supercapacitor applications
    (Springer Heidelberg, 2025) Kaya, Harun; Korkmaz, Aydan Aksogan; Guler, Seher; Atalay, Funda Ersoy
    Natural specularite ore was investigated as a sustainable and low-cost raw material for supercapacitor electrodes. This study provides new insight by demonstrating the direct conversion of an abundant iron ore into a functional nanostructured electrode (nano sp/NF) through a combined process of planetary ball milling, ultrasonic exfoliation in N, N-dimethylformamide, and hydrothermal treatment. The fabricated electrode exhibited a specific capacitance of 425 F/g at 20 A/g together with remarkable cycling stability over 10,000 charge-discharge cycles. These superior performances are associated with the enlarged surface area and porous architecture, which facilitate rapid ion transport and efficient Faradaic reactions. Overall, the findings highlight the originality of employing natural ores through environmentally friendly and scalable processing routes, offering a promising pathway toward next-generation energy storage electrodes.
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    Evaluation of optimum carbonization conditions of the blended domestic polymeric waste, biomass and lignite in the presence of catalyst by Taguchi and ANOVA optimization analysis
    (Elsevier, 2022) Basar, Canan Akmil; Korkmaz, Aydan Aksogan; Onal, Yunus; Utku, Tugba
    In this work, the effects of blending mass ratio, pyrolysis temperature, pyrolysis time, heating rate, and amount of catalyst on the pyrolysis of the blended lignite (EL), pistachio shell (PS) and domestic wastes (DW) were investigated. The influence of experimental parameters on the char, liquid and gas efficiency was statistically evaluated by the Taguchi method and ANOVA analysis. The optimum experimental conditions is a1b1c2d1e3, a3b1c1d1e2, a2b3c2d3e2 for liquid efficiency, char efficiency and gas efficiency respectively. The amount of catalyst was found to be the most effective parameter for solid efficiency and the mass ratio for both liquid and gas efficiency. The char, liquid and gas efficiencys estimated by the Taguchi method under optimum experimental conditions are 39.58%, 18.5% and 47.04%, respectively. The char efficiency of 42.54%, liquid efficiency of 19.78% and gas efficiency of 49.83% were determined under optimum experimental conditions obtained by the Taguchi method. Analysis of Variance (ANOVA) was also used to determine the mean response magnitudes of each controllable process parameter. ANOVA analysis results support the results found by the Taguchi method. In the carbonization process, FTIR, XRD and SEM analyzes were performed to determine the structural change of the solid product depending on the temperature.
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    Implementation of Taguchi method, ANOVA and regression analyses to enhance char yield by carbonization in lignite-biomass blended
    (Taylor & Francis Inc, 2024) Korkmaz, Aydan Aksogan; Toptas, Yeliz
    Energy is a basic need for modern societies. Renewable energy refers to producing and using energy without harming the environment and without consuming resources. The transition to renewable and sustainable energy can provide many environmental, economic and social benefits. Academic research plays an important role in achieving this transition. Sustainable energy is critical to protecting the environment, promoting economic development and supporting social improvements. The transition to sustainable energy is a necessity for the future of humanity. For this purpose, in this study, lignite and biomass (apricot kernel shell) carbonization experiments were carried out under different conditions. Mixing ratio (Lignite/Biomass (w/w 1:1, 1:2, 1:3)), temperature (400 degrees C, 500 degrees C, 600 degrees C) and heating rate (10 degrees C/min, 30 degrees C/min, 50 degrees C/min) were determined as variable parameters. Taguchi's experimental design was used to optimize the parameters. The orthogonal array design plan was determined as L9 according to the available variables (33 x 33). Since the study aimed to obtain clean solid fuel, char yields were taken into account from the results. Signal-to-noise (S/N) ratios were calculated based on the larger the better condition. As a result of the carbonization experiments performed under Taguchi optimization conditions, it was determined that the S/N ratio was 31.73 and the char yield was 40.19%. Since the estimated char yield with the Taguchi method was 38.85%, it was concluded that the optimization was achieved with 96.67% accuracy. The test parameters satisfying these conditions were determined as 1:1 lignite/biomass mixing ratio, 400 degrees C temperature and 30 degrees C/min heating rate. As a result of the ANOVA analysis, it was seen that the heating rate did not have a significant effect on these parameters. In contrast, the temperature and mixing ratio were important variables. Also, regression analysis (linear and quadratic) was used in this study to calculate the equations for the prediction of char yield. It was concluded that the linear regression model was more successful in estimating the char yield.
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    Interpretation of combustion properties of raw-pyrolyzed lignite with kinetic data
    (Taylor & Francis Inc, 2023) Korkmaz, Aydan Aksogan; Akbulut, Yeliz
    This study investigated the pyrolysis properties and kinetic behavior of Ermenek (Konya, Turkey) lignite. For this purpose, lignite was carbonized at 500 degrees C and different heating rates (5, 10, 15, and 20 degrees C/min). Proximate, elemental, XRF, and TGA-DTA lignite and chars were performed. Thermal analyses were performed at a heating rate of 10 degrees C/min from room temperature to 1000 degrees C and an inert (N-2) gas flow of 50 ml/min. Peak temperatures and mass losses were determined from the data obtained from the experiments. By examining the thermogram curves, three different temperature regions depended on moisture loss, the release of volatile matter, and fixed carbon combustion. In addition, from these data, kinetic calculations were performed using Arrhenius and Coats-Redfern approaches, and the apparent activation energies were calculated for each region. The activation energy values calculated according to the Coats-Redfern kinetic model are significantly lower than those calculated according to the Arrhenius kinetic model. The highest activation energies calculated were: for Region 1 and Region 2 at 5 degrees C/min heating rate and for Region 3 at 10 degrees C/min heating rate.
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    Structural and electrochemical evaluation of ball-milled natural specularite ore for supercapacitor applications
    (Elsevier Science Sa, 2026) Korkmaz, Aydan Aksogan; Kaya, Harun; Guler, Seher; Atalay, Funda Ersoy
    The widespread availability, high theoretical specific capacitance, and low cost of transition metal oxides, such as iron, make them promising candidates for electrode materials in energy storage applications. Among these nanostructured iron oxides, hematite is a highly preferred material for supercapacitor anodes due to its low cost, non-toxicity, high abundance, and the availability of various oxidation states. This study investigates the unique characteristics of natural (raw) specularite ore, also known as mica hematite, as a supercapacitor electrode material. We employed manual grinding and ball milling methods to reduce the particle size of specularite ore. The sample's morphological, chemical, and structural characteristics were analyzed using XRF, DTA/TGA, XRD, BET, and SEM/EDX, revealing its distinct properties that set it apart from other materials. The electrochemical properties of the specularite ore, ground to the nanoscale using a ball mill, were rigorously evaluated through cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. The results showed that the specularite electrode exhibited pseudo-capacitive characteristics, with a specific capacitance of 80.6 F g-1 and a stable initial capacitance of 50 F g-1 after 1000 cycles. These findings have significant implications for the practical use of specularite in energy storage applications.
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    Sustainable approach to dye adsorption: hemp-based activated carbon as an effective adsorbent
    (Taylor & Francis Ltd, 2024) Toptas, Yeliz; Yavuz, Bahar; Korkmaz, Aydan Aksogan; Onal, Yunus
    In industry, the use of dyes that threaten human health is increasing day by day. RB 19 (Reactive Blue 19, Remazol brilliant blue R), one of the most common dyes that adversely affect natural life, is the subject of this article. In this article, the waste parts of the hemp plant (root, stem and other) were evaluated for use in scientific studies. Hemp wastes were carbonised at 500 degrees C at a heating rate of 10 degrees C/min for 1 hour in the N2 atmosphere. Chemical activation was then carried out with 1:4 potassium hydroxide (KOH) at 800 degrees C under the same conditions. Activated carbon (AC) used as an adsorbent was characterised by elemental analysis (73.3% C, 0.3% H, 0.46% N, 0.02% S and 25.92% O), XRD, SEM, BET and FT-IR analysis. Activated carbon (AC) with 850 mu m size, 1858.70 m2/g surface area was obtained by chemical activation of carbonised hemp waste with KOH. SEM images showed that the activated carbon is structurally similar to a honeycomb. Kinetic parameters were analysed with six different equations (Intra Particle Diffusion, Pseudo First, Pseudo Second, Elovich, Avrami, Bangham) and adsorption mechanism with eight different equations (Henry, Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Koble-Corrigan, Flory-Huggins, Harkin-Jura). According to the calculated diffusion coefficient (19.299), it is concluded that diffusion is externally controlled. The Intra-Particle Diffusion constant (75.34) indicated that the outer adsorption layer of activated carbon was thick. When the correlation coefficients of the equations were examined according to the kinetic analysis results, the highest correlation coefficient was observed in the Pseudo-First kinetic model for all temperatures. However, it was determined that it also fits the Bangham and Avrami models. Since Bangham and Avrami models have high regression coefficients (0.96-0.99), it can be said that adsorption also fits these models. Also, the negative Gibbs Free Energy values indicate that adsorption can occur spontaneously and is thermodynamically favourable.
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    Thermokinetic Mapping of Activation Energy Evolution from Biomass to Biochar and Activated Carbon
    (Taylor & Francis Inc, 2026) Korkmaz, Aydan Aksogan; Kaya, Harun; Ersoy Atalay, Funda
    Introduction: Understanding the thermokinetic evolution of biomass-derived carbons is critical for optimizing their structural stability and functional performance in advanced applications. Agricultural residues, such as pepper, tomato, and eggplant waste, offer sustainable carbon precursors; however, the evolution of activation energy during their transformation into biochar and activated carbon remains poorly understood. Methodology: Raw biomass, derived biochars, and KOH-activated carbons were systematically investigated using thermogravimetric analysis under controlled heating conditions. Kinetic parameters were determined by combining the Arrhenius, Coats - Redfern, and isoconversional Kissinger - Akahira - Sunose/Ozawa - Flynn - Wall models to track changes in activation energy throughout the conversion pathway. Results and Discussion: The materials exhibited multistage thermal degradation behavior, with significant mass losses associated with hemicellulose and cellulose decomposition between 200 and 400 degrees C. Progressive shifts of Tmax toward higher temperatures and increased residual mass from biomass to activated carbon indicated enhanced carbon consolidation and thermal stability. Activation energy increased systematically from raw biomass (-66 to 55kJ mol-1) to biochar (63-93kJ mol-1), reaching up to 118kJ mol-1 for activated carbons, reflecting a transition to carbon lattice - controlled kinetics. Conclusion and Recommendations: This study elucidates the structure - reactivity transformation from biomass to engineered carbons driven by aromatization and stabilization. The presented thermokinetic mapping provides a rational framework for designing biomass-derived carbons tailored for adsorption, catalysis, and energy storage applications.