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    High- Performance Supercapacitor Electrode Based on NiFe Nanowire Networks/PEDOT:PSS
    (Elsevier Ltd, 2020) Ersoy Atalay, Funda; Şener, Melike; Kaya, Harun
    In 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
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    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, Funda
    The 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.
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    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, Sema
    In 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.
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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.