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    Binary nanocomposites of reduced graphene oxide and cobalt (II, III) oxide for supercapacitor devices
    (Taylor & Francis Ltd, 2022) Ates, Murat; Yoruk, Ozan; Bayrak, Yuksel
    In this study, a simple and one-step cost-effective preparation of rGO/Co3O4 nanocomposite was given out in different monomer concentrations of [rGO]o/[Co3O4]o= 1:1; 1:2; 1:5 and 1:10. The electroactive materials were characterized by many techniques, such as FTIR-ATR, XPS, TGA-DTA, Raman, BET surface analysis, GCD, SEM-EDX, XRD, TEM, CV, and EIS analysis. A symmetric supercapacitor applying rGO/Co3O4 nanocomposite as positive and negative electrodes was taken in the potential window between 0.0 and 0.8 V as the highest specific capacitance of Csp= 115.35 Fxg-1 at 2 mVxs-1 for [rGO]o/[Co3O4]o= 1:2. Furthermore, the highest energy (E) and power densities (P) were obtained as E= 20.16 Whxkg-1 at 40 mA and P= 26.140 kWxkg-1 at 10 mA for [rGO]o/[Co3O4]o= 1:2 by GCD method, respectively. As a result, rGO/Co3O4 nanocomposite at different monomer concentrations showed an easy synthesis, a sustainable approach, and a high electrochemical performances for energy storage devices.
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    Design and assembly of supercapacitor based on reduced graphene oxide/TiO2/polyaniline ternary nanocomposite and its application in electrical circuit
    (Springer, 2022) Yoruk, Ozan; Bayrak, Yuksel; Ates, Murat
    Supercapacitor devices are used as energy storage technology for electrical circuits. Graphene, metal oxide, and conducting polymers are used as electroactive materials to enhance energy, power density, and cycle life. The present study uses TiO2 and rGO materials, which are added to polyaniline (PANI). The nanocomposite structure can be observed using different initial feed ratios of rGO, TiO2, and aniline monomer as [rGO](o)/[TiO2](o)/[ANI](o) =1:5:1, 1:5:2, 1:5:3, 1:5:4, and 1:5:5. Fourier transform infrared-attenuation-transmission reflectance, scanning electron microscopy-energy-dispersive X-ray analysis, Brunauer-Emmett-Teller surface area, thermal-gravimetric analysis (TGA-DTA), X-ray diffraction (XRD), Raman spectroscopy, X-ray photon spectroscopy, and transmission electron microscopy analysis are conducted. Electrochemical performances of a ternary nanocomposite material are carried out by cyclic voltammetry, galvanostatic charge-discharge measurements, and electrochemical impedance spectroscopy (EIS). According to results, rGO/TiO2/PANI nanocomposite shows much better performance than its individual components in terms of specific capacitance, energy density, power density, and cycle life. The highest specific capacitance is obtained as C-sp = 692.87 F/g at 2 mV/s for [rGO](o)/[TiO2](o)/[ANI](o) =1:5:4. A new real circuit model of LRS (CR1)(QR(2)) is adopted to our device, which supplies enough energy to the light LED lamp (1.8 V) for 3 min. As a result, rGO/TiO2/PANI nanocomposite may be used as a promote candidate for energy storage systems. [GRAPHICS] .
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    Practical Synthesis of Pioglitazone: Ligand Substitution Reaction With Oxido Vanadium(IV) and Biological Activity
    (Taylor & Francis Inc, 2013) Altun, Ozlen; Kucuktepe, Caner; Yoruk, Ozan; Feyizoglu, Adilhan
    The authors performed two types of experiments: the reduction of 5-{4-[2-(5-ethyl-2-pyridyl)etoxy]benzilidine}-24- thiazolidinedione to pioglitazone (5-{4-[2-(5-ethyl-2-pyridyl) etoxy]benzil}-24-thiazolidinedione) with magnesium/methanol and the synthesis of an oxidovanadium(IV) complex of pioglitazone in methanol under refluxing conditions. The structures of pioglitazone and its oxidovanadium(IV) complex were analyzed by using physicochemical and spectroscopic techniques. Comparisons of the spectral measurements of pioglitazone with those of its oxidovanadium(IV) ion complex are useful in determining the atoms of the ligand that are coordinated to the metal ion. In addition, antibacterial and antifungal activities of the complex were studied and the complex is screened against bacteria and fungi.
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    Reduced graphene oxide/Titanium oxide nanocomposite synthesis via microwave-assisted method and supercapacitor behaviors
    (Elsevier Science Sa, 2017) Ates, Murat; Bayrak, Yuksel; Yoruk, Ozan; Caliskan, Sinan
    In this paper, graphene oxide (GO) was firstly synthesized by modification of Hummers method from the literature. Secondly, reduced graphene oxide (rGO)/Titanium oxide (TiO2) nanocomposites were synthesized with different wt/wt % of GO/TiO2 (1:1; 1:2; 1:5 and 1:10) by microwave-assisted method. By treating GO and GO/TiO2 nanocomposites in a microwave oven, reduced graphene oxide (rGO) and rGO/TiO2 materials could be obtained within power of 180 Win 10 min. The weight ratio of rGO and TiO2 was used to obtain the optimum conditions for nanocomposite materials. The rGO/TiO2 nanocomposite active materials were characterized by cyclic voltammetry (CV), Fourier-transform infrared - Attenuated total reflectance (FTIR-ATR), scanning electron microscopy-energy dispersion X-ray (SEM-EDX), thermogravimetry (TGA), differential thermal analyzer (DTA) and electrochemical impedance spectroscopy (EIS) analysis. Thirdly, supercapacitors were fabricated as a symmetric device with two electrode configuration. The device performances were tested by CV, galvanostatic constant current (CC), and EIS measurements. TGA analysis indicated that the thermal stability of the nanocomposites improved from rGO (40% at 892.8 degrees C) to nanocomposite as the initial feed ratio of [GO](o)/[TiO2](o) = 1/10 as (94% at 949.3 degrees C) increased. The result show that the as-prepared symmetrical rGO/TiO2 nanocomposite on the two-electrode system displays very high specific capacitance of 524.02 F/g at 2 mV/s for [GO](o)/[TiO2](o) = 1/5 with a high energy density of E = 50.07 Wh/kg at 2 mV/s for [GO](o)/[TiO2](o) = 1/1 and high power density of P = 58.6 kW/kg at a the scan rate 1000 mV/s for [GO](o)/[TiO2](o) = 1/1. Additionally, the symmetric electrode shows good cycling stability with a retention value of 6.6% for [GO](o)/[TiO2](o) = 1/1 after 1000 cycles. These good results suggest us that rGO/TiO2 nanocomposite which is obtained by microwave-assisted method has a great potential as an electrode material for supercapacitor applications. The equivalent circuit model of R-s(C-dl(RctW)) was used to explain parameters of solution resistance, double layer capacitance (Cdl), charge transfer resistance (R-ct), Warburg impedance (W). Theoretical and experimental values support with each other. (C) 2017 Elsevier B.V. All rights reserved.
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    Reliability of electrode materials for supercapacitors and batteries in energy storage applications: a review
    (Springer Heidelberg, 2022) Ates, Murat; Chebil, Achref; Yoruk, Ozan; Dridi, Cherif; Turkyilmaz, Murat
    Supercapacitors and batteries are among the most promising electrochemical energy storage technologies available today. Indeed, high demands in energy storage devices require cost-effective fabrication and robust electroactive materials. In this review, we summarized recent progress and challenges made in the development of mostly nanostructured materials as well as fabrication routes for energy storage devices. Indeed, we systematically sorted out the design principles of electrode materials such as lithium-ion, lead-acid, lithium-sulfur, nickel-cadmium, nickel-metal hydride, and sodium-ion for rechargeable batteries electrode and supercapacitors (SCs) electrode materials following by systematic discussions on electric double-layer capacitors, pseudocapacitors, and hybrid SCs behavior.
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    rGO/CuO/PEDOT nanocomposite formation, its characterisation and electrochemical performances for supercapacitors
    (Taylor & Francis Ltd, 2019) Ates, Murat; Garip, Alpay; Yoruk, Ozan; Bayrak, Yuksel; Kuzgun, Ozge; Yildirim, Murat
    Supercapacitor properties of rGO, CuO, PEDOT and rGO/CuO at [rGO](o)/[CuO](o) = 1:1; 1:1.5; 1:2 and rGO/CuO/PEDOT nanocomposite at [rGO](o)/[CuO](o)/[EDOT](o) = 1:1:1; 1:1:3; 1:1:5 were investigated using chemical reduction of GO and in-situ polymerisation process. SEM-EDX, HRTEM, BET surface area analysis confirm the nanocomposite formations. Nanocomposite materials are also analysed through FTIR-ATR, Raman, TGA-DTA, GCD, CV and EIS. The highest specific capacitance of C-sp = 156.7 F/g at 2 mV/s is determined as rGO/CuO/PEDOT at [rGO](o)/[CuO](o)/[EDOT](o) = 1:1:5. In addition, two-electrode supercapacitor device for rGO/CuO/PEDOT at [rGO](o)/[CuO](o)/[EDOT](o) = 1:1:5 are found to provide a maximum specific energy (E = 14.15 Wh/kg at 20 mA) and specific power (P = 24730 W/kg at 50 mA), electrical serial resistance (ESR = 13.33 omega) with good capacity retention after 3000 cycles. An equivalent circuit model of LR1(CR2)(QR3) is proposed to interpret the EIS data. The supercapacitor performance of the rGO/CuO/PEDOT nanocomposite electrode indicates the synergistic effect of hybrid supercapacitors.
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    Supercapacitor performances of RuO2/MWCNT, RuO2/Fullerene nanocomposites
    (Wiley, 2019) Ates, Murat; Kuzgun, Ozge; Yildirim, Murat; Yoruk, Ozan; Bayrak, Yuksel
    In this study, RuO2/Fullerene and RuO2/MWCNT nanocomposites were synthesized to use as an electroactive materials in symmetric supercapacitor device performances. The materials were examined via Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), thermo-gravimetric analysis (TGA-DTA), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS). The RuO2/MWCNT and RuO2/Fullerene nanocomposite electrodes show good electrochemical performances. For instance, the highest specific capacitance of RuO2/Fullerene and RuO2/MWCNT electrodes reaches C-sp = 3895.11 and 1662.19F/g at 1mV/s within the potential range of 0.8 V in 1 M H2SO4 solution. RuO2/MWCNT and RuO2/Fullerene nanocomposites have good cycle stability similar to 100% specific capacitance at [RuO2](o)/[MWCNT](o) = 1:1; 2:1 and [RuO2](o)/[Fullerene](o) = 2:1, respectively. The different equivalent circuit models of LR(1)Q(C1R2) and LR1(Q(1)R(2))(Q(2)R(3)) were used to interpret EIS data.
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    Symmetric supercapacitor device applications of rGO / Co3O4 / polypyrrole nanocomposites
    (Springer Heidelberg, 2022) Ates, Murat; Yoruk, Ozan; Bayrak, Yuksel
    Symmetric supercapacitor electrode design and synthesis of micro-nano structured metal oxide (Co3O4) and polypyrrole with reduced graphene oxide (rGO) have played an important role in supercapacitor investigations. The characterizations of rGO/Co3O4/PPy nanocomposites were given by FTIR-ATR, SEM-EDX, TGA-DTA, BET surface, and porous analysis and Four-point probe analysis. The symmetric rGO/Co3O4/PPy supercapacitor devices were presented in different initial feed ratios of [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:1; 1:5:2; 1:5:5 and 1:5:10 for 2 M and 6 M KOH solutions. The highest specific capacitances, energy and power densities of C-sp = 896 F x g(-1), E = 31.75 Wh x kg(-1) and P = 11,705 W x kg(-1) for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:10 in 2 M KOH solution and C-sp = 1370 F x g(-1) for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:5 and E = 31.43 Wh x kg(-1) and P = 11,600 W x kg(-1) for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:1 in 6 M KOH solution. The lowest capacitance retention was obtained as 3.69% in 2 M KOH solution for [rGO](o)/[Co3O4](o)/[Py](o) = 1:5:1 after 1000 cycle charge/discharge performances by CV method. Symmetric supercapacitor of rGO/Co3O4/PPy should open up new opportunities for the next-generation high-performance supercapacitors.
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    Synthesis of rGO/TiO2/PEDOT nanocomposites, supercapacitor device performances and equivalent electrical circuit models
    (Springer, 2019) Ates, Murat; Bayrak, Yuksel; Ozkan, Haydar; Yoruk, Ozan; Yildirim, Murat; Kuzgun, Ozge
    A new nanocomposite electrode incorporating poly(3,4-ethylenedioxythiophene) (PEDOT) within the nanocomposite film of the reduced graphene oxide / Titanium dioxide (TiO2) was synthesized to be used in supercapacitor devices. We used constant EDOT monomer for in-situ polymerization and different initial monomer concentration ratio of [rGO](o)/[TiO2](o)=1/1, 1/2 and 1/5. The obtained nanocomposites were examined by FTIR-ATR, UV-vis, SEM-EDX, TGA-DTA, BET surface areas and pore distribution, XRD, TEM, AFM, CV, GCD and EIS analyses. The results showed that graphene oxide was successfully reduced to rGO by means of the microwave-assisted method. It was confirmed by the increases in the specific capacitance of (C-sp=652F/g) at 1mV/s for the rGO/TiO2/PEDOT nanocomposite at [rGO](o)/[TiO2](o)=1/5. This was related to the pore size (similar to 33.50nm) of the material for rGO/TiO2/PEDOT at [rGO](o)/[TiO2](o)=1/5 obtained from BET analysis. The other C-sp values were 475.33F/g for [rGO](o)/[TiO2](o)=1/2, 114.09F/g for rGO/PEDOT and 48.02F/g for [rGO](o)/[TiO2](o)=1/1. Equivalent circuit model of R-ct(CdlRct) was analyzed via ZSimpWin and TINA programmes. A facile and inexpensive approach for a ternary nanocomposite synthesis of rGO/TiO2/PEDOT was presented for future supercapacitor applications.