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- ArticleYalnız künye2024Development of a novel hydrothermal process for surface modification of galvanized steel, characterization, and photocatalytic application
Zorlu, Rabia; Özdokur, K. Volkan; Acımert, Özlem Baran; Demir, Zeynep; Çağlar, Bülent; Çırak, Çağrı; Koçak, Süleyman
In this study, the hydrothermal surface modification of galvanized steel was performed on the substrate without any precursor ion for the first time to achieve a photocatalytic activity under UV light irradiation. The structural, morphological and optical properties of the modified and bare samples were examined by XRD, SEM-EDX, XPS, FTIR, UV-DRS and PL analyses. Electrochemical and wettability properties were determined with potentiostat and contact angle goniometry, respectively. The photocatalytic performances of surface modified galvanized steel samples were also investigated and comparatively evaluated by photo-degradation of quinoline yellow dye under UV light irradiation. Upon the doping silver ions into the structure, the photocatalytic degradation efficiency of fabricated composite material was determined as 100 % after the periods of 65 min. To the best of our knowledge this study is the first study dealing with photodegradation of quinolone yellow by using modified galvanized samples. The modified galvanized steel samples exhibited 96.1 % of its initial activity after 5 cycles. The surface modification by hydrothermal treatment improved the electrochemical properties of galvanized steel.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2022Gold-Nanoparticles-Decorated ZrO2-CuO Nanocomposites: Synthesis, Characterization and A Novel Platform for Electrocatalytic Formaldehyde Oxidation
Özdokur, Kemal Volkan; Koçak, Çağrı Ceylan; Eden, Çiğdem; Demir, Zeynep; Çirak, Çağrı; Yavuz, Emre; Çağlar, Bülent
In this study, gold nanoparticles decorated copper oxide- zirconium oxide mixture has been deposited on glassy carbon electrode surface by simple electrochemical technique. The obtained composite surface has been investigated by electrochemical impedance spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy in detail. The results of SEM images, XPS and XRD data indicated the surface of ZrO2-CuO composite was successfully decorated with Au nanoparticles. The resulting ZrO2-CuO/Au nanocomposite contained about 1.48 % Au nanoparticles with 70 nm average diameter. Then, the catalytic performance of ZrO2-CuO/Au nanocomposites was investigated by using formaldehyde oxidation. The comparative studies have been revealed that the ZrO2-CuO/Au nanocomposites exhibited a better current density towards formaldehyde oxidation than that of bare, ZrO2-CuO, and Au modified electrodes in alkaline media. According to the best of our knowledge, this is the first study dealing with the usage of ZrO2-CuO/Au nanocomposites in formaldehyde oxidation. As the electrochemically fabricated, stable ZrO2-CuO/Au surface improved catalytic activity towards formaldehyde oxidation, this material is a promising candidate for application in fuel cells and removal of formaldehyde from aqueous solutions.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2020Graphene/polyaniline nanocomposite as platinum-free counter electrode material for dye-sensitized solar cell: its fabrication and photovoltaic performance
Bayram, Ozkan; Igman, Erdal; Guney, Harun; Demir, Zeynep; Yurtcan, Mustafa Tolga; Cirak, Cagri; Hasar, Ugur Cem; Simsek, Onder
In this study, it was aimed to produce graphene/polyaniline nanocomposite thin films as counter electrode materials by PECVD system and to determine the photovoltaic performances of these counter electrodes in dye-sensitized solar cells (DSSCs). Graphene/polyaniline counter electrode (GPCE) material was produced in two different steps. Firstly, a single-layer and multilayer graphene thin films were produced on the fluorine-doped tinoxide (FTO) substrates. Then, polyaniline (PANI) thin films were grown on each graphene thin films using plasma polymerization technique, and eventually the production of the graphene/PANI nanocomposite was completed. The fabricated graphene/PANI nanocomposites were used in place of platinum (Pt)-counter electrode which is widely used in DSSCs and the photovoltaic performance of these counter electrodes was investigated. The DSSCs consisted of titanium dioxide (TiO2) nanotube photoanode, N719 dye, iodolyte liquid electrolyte, and graphene/PANI nanocomposite counter electrode. I–V measurements were carried out in order to calculated photoconversion efficiency (PCE) and it was found that the these efficiency of GPCEs changed between 0.56 and 1.36% according to the number of graphene layers. The photovoltaic performance of DSSC, consisting of TiO2 nanotube photoanode and Pt-counter electrode was 1.1%.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2020The enhanced light harvesting performance of dye-sensitized solar cells based on ZnO nanorod-TiO2 nanotube hybrid photoanodes
Bozkurt Çırak, Burcu; Eden, Çiğdem; Erdoğan, Yaşar; Demir, Zeynep; Özdokur, K. Volkan; Caglar, Bulent; Morkoç Karadeniz, Sibel; Kılınç, Tuba; Ercan Ekinci, Ali; Çırak, Çağrı
In this study, TiO2/ZnO hybrid nanocomposites (TZ) were fabricated by two step synthesis route for potential applications as photoanode in dye sensitized solar cells (DSSC). Titania nanotubes were grown on titanium sheets by electrochemical oxidation. ZnO nanorods were decorated with hydrothermal method by equimolar (0.1 M) precursors on TiO2 nanotubes. Hydrothermal temperatures values were changed to find the optimal ZnO decoration density to increase photo conversion efficiency. The characterization of the photoanodes was made using FE-SEM, XRD and XPS techniques. The results show that hydrothermal reaction temperature can dramatically enhance the light harvesting performance of TZ photoanodes. The photo conversation efficiency of DSSC by TZ photoanode was reached 1.67 % for hydrothermal temperature of 130 °C which is twofold higher than that of DSSC by TiO2 nanotubes (0.81 %). The improvement in photo conversation conversion efficiency can be assigned to synergetic effect in TZ photoanode, lower recombination rate and charge transfer resistance.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Facile synthesis of hybrid ZnO nanostructures by combined electrodeposition and chemical bath deposition for improved performance of dye-sensitized solar cell
Boda, Muzaffar Ahmad; Bozkurt Çırak, Burcu; Demir, Zeynep; Çırak, Çağrı
Herein, equimolar hexamethylenetetramine (HMT) were used to couple chemical bath deposition (CBD) and electrode deposition (ED) techniques to decorate electrodeposited one-dimensional (1-D) ZnO nano-rods with wurtzite nano-spindles in the attempt of increasing surface area to fabricate efficient and cost-effective dye sensitized solar cell (DSSC) photo-anode. The resulting hybrid photo-anode offers an enhancement of 43% in photocurrent density than bare ZnO nano-rods. The corresponding augmentation in photocurrent response is attributed to comparative increase in crystallinity and considerable decrease in charge transfer resistance across the interface as being analyzed by X-ray diffraction and electrochemical impedance spectroscopy (EIS), respectively.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Synthesis of TiO 2 nanotube/ZnO nanorod hybrid nanocomposite photoanodes for dye-sensitized solar cells
Çırak, Burcu Bozkurt; Demir, Zeynep; Eden, Çiğdem; Erdoğan, Yaşar; Caglar, Bulent; Karadeniz, Sibel Morkoç; Kılınç, Tuba; Ekinci, Ali Ercan; Çırak, Çağrı
TiO 2 nanotube/ZnO nanorod hybrid nanocomposite (ZTN) photoanodes were synthesized, characterized and assembled as dye-sensitized solar cells (DSSCs) at optimum conditions for improving photovoltaic efficiency. The self-organized and high ordered TiO 2 nanotube arrays were growth on titanium foil by anodic oxidation as a substrate for ZnO decoration by hydrothermal method. Zinc nitrate hexahydrate and hexamethylenetetramine precursor concentrations were varied to designate the optimum ZnO decoration density for enhanced photoconversion efficiency. XRD, FESEM and XPS results showed that the crystal structure, morphology, elemental composition and density of ZnO nanorods on the surface of TiO 2 nanotubes are very sensitive to ZnO precursor concentrations. It is found that, the highest overall efficiency of DSSC based on ZTN photoanode was measured 1.8% for precursor concentration of 60 mM which was more than double compared to DSSC based on bare-TiO 2 nanotubes (0.8%). The improvement of DSSC efficiency originates from suppressing the recombination rate and decreasing the charge transfer resistance due to synergetic effect between TiO 2 nanotubes and ZnO nanorods.
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