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SARIOĞLU, CEVAT

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Author: UĞUZ NELİ, ÖZLEM × End date: 2023 ×

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    Photoelectrochemical performance of thermally sulfurized CdxZn1-xS photoanode: Enhancement with reduced graphene oxide support
    (PERGAMON-ELSEVIER SCIENCE LTD, 2020) ÖZKAYA, ALİ RIZA; Ayaz, RanaMuhammad Zunain; Akyuz, Duygu; Uguz, Ozlem; Tansik, Irem; Sarioglu, Cevat; Karaca, Fatma; Ozkaya, Ali Riza; Koca, Atif
    In this study, photoelectrochemical performance of reduced graphene oxide (RGO)-CdxZn1-xS compos-ites, which were synthesized through a novel two-steps thermal sulfurization process by using elemental sulfur, was reported. This is the first time that the two-step thermal sulfurization process with elemental sulfur for the preparation of photoanode based on RGO-CdxZn1-xS. The electrodes exhibited high photostability and photocurrent response in the presence of visible light. The presence of RGO in CdxZn1-xS as electron collector and transporter increased the photocurrents approximately 40%. Among the RGOCdxZn1-xS composites, RGO-CdS photoanode yielded an extremely high photocurrent density of 6.5 mAcm(-2) with the rate of hydrogen production rate of 551.1mmolh(-1)cm(-2). This value of photocurrent density is almost 89% of its theoretical value. This is the maximum attained photocurrent density with superior stability in comparison with related literature. (c) 2020 Elsevier Ltd. All rights reserved.
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    Metal chalcogenide based photocatalysts decorated with heteroatom doped reduced graphene oxide for photocatalytic and photoelectrochemical hydrogen production
    (PERGAMON-ELSEVIER SCIENCE LTD, 2019) ÖZKAYA, ALİ RIZA; Akyuz, Duygu; Ayaz, Rana Muhammad Zunain; Yilmaz, Seda; Uguz, Ozlem; Sarioglu, Cevat; Karaca, Fatma; Ozkaya, Ali Riza; Koca, Atif
    Heteroatom (N, B and P) doped reduced graphene oxide (RGO)-metal chalcogenide nanocomposites (RGO-Cd0.60Zn0.40S) were prepared by the solvothermal method, and then they were characterized with X-ray diffraction, Raman spectroscopy, transmission electron microscopy, high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, UV-Vis diffuse reflectance spectroscopy and photoluminescence techniques. Doping of RGO with heteroatoms of N, B and P increased charge-transfer capability of nanocomposites and thus, improved both photocatalytic and photoelectrochemical hydrogen production activities of them. N-doped RGO-Cd0.60Zn0.40S photocatalyst exhibited the highest photocatalytic hydrogen production rate (1114 mu molh(-1) g(-1)) in photocatalytic (PC) system amongst other and it was 1.5 times higher than that of RGO-Cd0.60Zn0.40S photocatalyst. Having a current density of 0.92 mAcm(-2), photoelectrochemical hydrogen production activity of N-RGO-Cd0.60Zn0.40S electrode was found to be 3 times higher than RGO-Cd0.60Zn0.40S photoelectrode without any applied bias potential under visible light irradiation in photoelectrochemical system. In general, these results clearly showed that heteroatom doping of RGO led to promising materials for renewable hydrogen production in the photocatalytic and photoelectrochemical systems. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    Solar-hydrogen production with reduced graphene oxide supported CdxZn1-xS photocatalysts
    (PERGAMON-ELSEVIER SCIENCE LTD, 2020) ÖZKAYA, ALİ RIZA; Tanisik, Irem; Uguz, Ozlem; Akyuz, Duygu; Ayaz, Rana Muhammad Zunain; Sarioglu, Cevat; Karaca, Fatma; Ozkaya, Ali Riza; Koca, Atif
    Reduced graphene oxide (RGO)/CdxZn(1-x)S composites were firstly synthesized by thermal sulfurization method in one pot with elemental sulfur as sulfur source. By using one pot synthesis, CdxZn(1-x)S particles were decorated on the RGO sheets during sulfurization of Cd2+ and Zn2+ precursors. This synthesis method eased the control of the particle sizes of CdxZn(1-x)S by providing homogenous decoration of RGO with CdxZn(1-x)S particles and increased the strength between RGO sheet and CdxZn(1-x)S particles, which enhanced charge carrier mobility rate. Here, RGO in the composite structure supplied high electron conductivity, high adsorption capacity and extended light absorption ability. Thus, prepared RGO/CdxZn(1-x)S composites enhanced the photocatalytic activity. The crystal systems, lattice parameters, band gaps and surface morphologies of all photocatalysts are characterized to determine the factors that affected the photocatalytic activities of the composites. After that, the photocatalytic activities of prepared photocatalysts were tested by measuring H-2 evolution rates. Among the composites, RGO/Cd0.7Zn0.3S structure possessed the highest H-2 production rate (141.6 mu molh(-1)) and apparent quantum efficiency (19.4%). (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.