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Öğe A GREEN APPROACH FOR DYE DECONTAMINATION: ACTIVATED CARBON FROM HEMP WASTE(Editura Acad Romane, 2025) Kaya, HarunIn this research, activated carbon was derived from hemp waste using a chemical activation technique, and methylene blue adsorption was tested. Hemp wastes were first carbonized at 500 degrees C, mixed at a 1:3 biochar/KOH ratio by mass, and activated at 800 degrees C. The equilibrium data's suitability to the Langmuir, Freundlich, and Harkin-Jura isotherms was investigated, and it was identified as compatible with the Langmuir isotherm. The maximum adsorption capacity (qm) was determined as 400.25 mg/g. Adsorption kinetics were analyzed with intraparticle diffusion, pseudo-first and pseudo-second models, and determined to fit the pseudo-second-order kinetic model (R2 = 0.9934). Since this method is inexpensive, it can be used effectively for eliminating methylene blue. From the results of the study, it is concluded that activated carbon from hemp waste is of strategic importance for environmental sustainability and water quality management.Öğe A RESEARCH ON ELECTRODE APPLICATIONS: SYNTHESIS OF NICKEL-DOPED GRAPHENE OXIDE(Munzur University, 2024) Kaya, HarunIn today's technology, carbon-based materials (such as graphene, graphene oxide, carbon nanotubes, etc.) have become one of the most important research areas due to a large number of applications. Graphene oxide (GO) is being investigated in many applications, especially in the energy field. In this study, GO was synthesized by a modified Hummer’s method. After the synthesis of GO, nickel addition to the struc-ture was made by the hydrothermal method. The morphological and structural prop-erties of the synthesized GO were characterized by scanning electron microscope (SEM), X-ray powder diffraction (XRD) and Brunauer–Emmett–Teller (BET). Ac-cording to the BET results, the surface areas of untreated GO and Ni-doped graphene oxide after heat treatment at 360°C (Ni-doped GO 360) were calculated as 3.22 m2 g-1 and 228 m2 g-1, respectively. Electrochemical properties of GO and Ni-doped GO 360 were analyzed using cyclic voltammetry (CV), long term charge/discharge analysis and impedance spectroscopy. At the end of 1000 cycles, it was determined that the Ni-doped GO 360 electrode retained 76% of its initial capacitance.Öğe 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, SeherBiomass-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.Öğe Different Plant Sporopollenin Exine Capsules and Their Multifunctional Usage(American Chemical Society, 2022) Atalay, Funda Ersoy; Culum, Ayşe Asiye; Kaya, Harun; Göktürk, Günay; Yiğit, Emelporopollenin exine capsules (SECs) are highly resistant to heat and various acids and bases. They are also cheap, highly porous, eco-friendly polymer biomaterials with stable microencapsulation capacity. Due to their strong and uniquely shaped exine layers, they can allow growth on metal oxide materials, as a biotemplate for use in different applications. In this study, first, a single SEC extraction method was applied to three different pollens from Pinus, Fraxinus excelsior, and Tilia. Scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, and thermogravimetric/differential thermal analysis (TGA/DTA) measurements both before and after the extraction process were performed to observe changes in surface area, morphology, porous structure, and degradation properties. The protein content and removal were analyzed by elemental and spectrophotometric analyses. Then, SECs were loaded by passive and centrifuge loading for drug delivery, and the loading capacities were analyzed by Fourier transform infrared spectroscopy and spectrophotometry. The method was successful in opening the pores and maintaining the structural integrity of SECs. It was determined that the morphology and porosity affected the encapsulation efficiency. According to the loading capacities, Tilia SECs were the most efficient SECs for both loading methods. In addition, three different SECs were hydrothermally coated with cobalt and then heat-treated to obtain a metal oxide structure. A CO3O4supercapacitor electrode constructed using CO3O4-F. excelsior SEC powder had the best surface area parameters. The electrode showed a maximum specific capacity of 473 F/g for over 3000 continuous cycles of galvanostatic charge-discharge (GCD). © 2022 American Chemical Society. All rights reserved.Öğe Electrode material development from natural specularite ore for supercapacitor applications(Springer Heidelberg, 2025) Kaya, Harun; Korkmaz, Aydan Aksogan; Guler, Seher; Atalay, Funda ErsoyNatural 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.Öğe The formation of RuO2 structures on cladosporium cladosporioides hyphal and an investigation of their properties(Adıyaman Üniversitesi, 2018) Kaya, HarunIn this study, ruthenium oxide (RuO2) was grown on Cladosporium Cladosporioides hyphal using a chemical precipitation method. The morphological characteristics of the material obtained by chemical precipitation method were determined by Scanning Electron Microscope (SEM); its surface area by Brunauer-Emmett-Teller (BET) equipment and its electrochemical properties, such as charging–discharging, cyclic voltammetry (CV) and electrochemical impedance characteristics, using a Gamry 3000 potentiostat system.Öğe High- Performance Supercapacitor Electrode Based on NiFe Nanowire Networks/PEDOT:PSS(Elsevier Ltd, 2020) Ersoy Atalay, Funda; Şener, Melike; Kaya, HarunIn this work, the usage of electrochemically produced NiFe nanowires (NW) as an electrode active material for supercapacitors has been investigated. Different concentrations of NiFe NWs were dispersed on thin conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films by spin coating system. NiFe NW networks/PEDOT:PSS electrode was used as a positive electrode in the three-electrode cell. Electrochemical capacitive performance tests such as; electrochemical impedance spectroscopy, galvanostatic charge-discharge tests (GCD) and cyclic voltammetry (CV) were performed in 1 M Na2SO4 electrolyte. The CV curves of the designed electrodes have been found to be similar to the CV curves of the ideal supercapacitor and they have almost rectangular in shape. The specific capacitance of 2 mg NW mass loading was evaluated 332 F/g at a current density of 2 A/g from GCD measurements with excellent cyclability up to 5000 times. These good electrochemical performances arise from network structure of NiFe NW based electrodeÖğe High-Performance Supercapacitor Electrode Based on NiFe Nanowire Networks/PEDOT:PSS(Elsevier, 2020) Atalay, Funda Ersoy; Sener, Melike; Kaya, HarunIn this work, the usage of electrochemically produced NiFe nanowires (NW) as an electrode active material for supercapacitors has been investigated. Different concentrations of NiFe NWs were dispersed on thin conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) films by spin coating system. NiFe NW networks/PEDOT:PSS electrode was used as a positive electrode in the three-electrode cell. Electrochemical capacitive performance tests such as; electrochemical impedance spectroscopy, galvanostatic charge-discharge tests (GCD) and cyclic voltammetry (CV) were performed in 1 M Na2SO4 electrolyte. The CV curves of the designed electrodes have been found to be similar to the CV curves of the ideal supercapacitor and they have almost rectangular in shape. The specific capacitance of 2 mg NW mass loading was evaluated 332 F/g at a current density of 2 A/g from GCD measurements with excellent cyclability up to 5000 times. These good electrochemical performances arise from network structure of NiFe NW based electrode. (C) 2019 Elsevier Ltd. All rights reserved.Öğe Juglans Sporopollenin for high-performance supercapacitor electrode design(American Chemical Society, 2020) Atalay, Funda Ersoy; Bingöl, Alper; Kaya, Harun; Emre, Yıldız; Baş, Hatice Hande; Culum, Ayşe AsiyeRecently, plant pollen has been used as a source of activated carbon to produce carbon-containing supercapacitor electrodes. However, in this study, pollen was used as a biotemplate with a completely different approach. As a biotemplate, pollen offers a wide range of varieties in terms of exterior, porosity, shape, and size. An electrode formed by the use of metal oxide grown on the pollen exine layer (sporopollenin microcapsules) as the active substance will inevitably exhibit good electrochemical capacitive properties. Juglans male flowers have been distinguished by dissection from anthers. Isolation of pollen grains from anthers was carried out using sieving from suitable sieves (45-200 mu m). Juglans sporopollenin exine microcapsules (SECs) were separated from the intine and protoplasm by acetolysis in combination with reflux. The solution containing SECs, metal ions, and Ni foam was put into a Teflon-lined hydrothermal container, and then, it was reacted at 120 degrees C for 15 h. The resulting precipitate, as well as the Ni foam, was heat-treated at 300 and 360 degrees C for 3 h in air. The raw pollen, chemically treated pollen, and cobalt-coated SEC (CoSEC) and CoSEC/Ni foam were characterized using scanning electron microscopy, Brunauer-Emmett-Teller surface area analysis, thermogravimetric analysis, and X-ray diffraction techniques. Two different types of supercapacitor electrode designs, with the use of exine microcapsules of Juglans sporopollenin, were performed for the first time. The maximum specific capacitance was up to 1691 F g(-1) at 5 A g(-1).Öğe Preparation and characterization of activated carbon from tomato, pepper, and eggplant wastes by two-step KOH activation(Taylor & Francis Inc, 2026) Yavuz, Bahar; Aksogan Korkmaz, Aydan; Kaya, Harun; Guler, Seher; Atalay, Funda ErsoyThis study investigates the morphological, structural, and chemical properties of activated carbons synthesized from common lignocellulosic agricultural wastes such as tomato, pepper, and eggplant residues. A two-step chemical activation method was employed. In the first step, the biomass was carbonized at 500 degrees C for 1 h to produce biochar. In the second step, the activation process was conducted at 800 degrees C for 1 h using different biochar:KOH impregnation ratios (1:1, 1:2, 1:3). The surface area of the resulting porous carbonaceous materials was determined by BET analysis, while their morphological features were examined by Scanning Electron Microscopy (SEM). Structural and chemical properties were characterized using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) techniques. The highest surface area values of activated carbons (2070-2254 m2/g) were obtained with a biochar:KOH weight ratio of 1:3. SEM images revealed the formation of a well-developed porous structure as a result of oxidation-reduction reactions. XRD analysis indicated the presence of graphite-like amorphous structures. FTIR spectra confirmed the presence of various surface functional groups, including C = C, C = O, C-H, C-C, and C-O. These findings demonstrate that widely available and low-cost agricultural wastes can serve as effective, environmentally friendly, and sustainable precursors for the production of activated carbon.Öğe A Rapid Response Humidity Sensor for Monitoring Human Respiration with TiO2-Based Nanotubes as a Sensing Layer(The Minerals, Metals & Materials Society, 2020) Atalay, Selçuk; Erdemoğlu, Sema; Kolat, Veli Serkan; İzgi, Tekin; Akgeyik, Emrah; Çağlar Yılmaz, Hatice; Kaya, Harun; Ersoy Atalay, FundaThe use of TiO2-based samples with nanotube (NT) shape for humidity sensing has been investigated. Sample characterization was carried out using x-ray diffraction analysis, scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy. x-Ray diffraction analysis showed that the nanotubes had TiO2, NaO3, and H2Ti2O5 phases. SEM revealed that the NTs had diameters ranging from 20 nm to 200 nm and very different lengths. TiO2-based nanotubes were coated using the drop-casting method onto a quartz crystal microbalance (QCM). The synthesis of TiO2-based NTs was performed using a hydrothermal process. Humidity sensing measurements showed that the resonant frequency of TiO2-based NTs deposited onto the QCM was very sensitive to humidity changes. It was also shown that the sensor could be used for respiratory monitoring purposes.Öğe Sol–gel synthesis of TiO2 on Co3O4-coated sporopollenin exine microcapsules (SECs) and photocatalytic performance of new semiconductor heterojunction material(Springer, 2022) Çağlar Yılmaz, Hatice; Ersoy Atalay, Funda; Kaya, Harun; Erdemoğlu, SemaIn this study, a new approach was developed to prepare mesoporous hybrid TiO2/Co3O4 coated on Juglans sporopollenin exine microcapsules (SECs). TiO2 was synthesized on Co3O4-coated SECs used as substrate, by sol–gel method. The obtained semiconductor/semiconductor hetero-junction hybrid materials were characterized with X-ray diffractometry (XRD), UV–Vis absorption spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), particle size distribution, specific surface area, and zeta potential measurements. Photocatalytic performances of hybrid materials were tested for Reactive Black 5 dye under both UV and visible light. Equilibrium pH of the solution containing 10 mg/L Reactive Black 5 dye and 0.1% wt/v TiO2/Co3O4 was around 4.7. After irradiation in the solar box, more than 98% of the Reactive Black 5 was photocatalytically degraded within 60 min.Öğe 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 ErsoyThe 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.Öğe Synthesis of NiO/SnO2 nanowires for energy applications(Polska Akademia Nauk, 2020) Kaya, HarunIn this study, SnO2 nanowire arrays with lengths in the micrometres range were successfully synthesised by using polyethylene glycol (PEG) at room temperature. Then Ni was coated onto the SnO2 nanowires by chemical precipitation. These nanowires were heat-treated at 360, 450, 500, and 650 degrees C to form various phases. X-ray powder diffraction studies showed that the heat-treated sample at 500 degrees C has a tetragonal rutile SnO(2 )phase. The Brunauer-Emmett-Teller surface area of the untreated Sn(COO)(2) nanowires was determined as 5.74 m(2)/g. After Ni coating and heat treatment at 360, 450, 500, and 650 degrees C, the surface areas of the NiO/SnO2 nanowires were measured to be 79.75, 33.38, 29.15, and 21.13 m(2)/g, respectively.Öğe Thermokinetic Mapping of Activation Energy Evolution from Biomass to Biochar and Activated Carbon(Taylor & Francis Inc, 2026) Korkmaz, Aydan Aksogan; Kaya, Harun; Ersoy Atalay, FundaIntroduction: 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.
