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SARIOĞLU, CEVAT

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Author: KOCA, ATIF × Subject: CDS ×

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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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    Photocatalytic-electrocatalytic dual hydrogen production system
    (PERGAMON-ELSEVIER SCIENCE LTD, 2016) ÖZKAYA, ALİ RIZA; Aydemir, Mehmet; Akyuz, Duygu; Agopcan, Burag; Sener, M. Kamm; Albayrak, Fatma Karaca; Sarzoglu, Ceuat; Koca, Atif
    In this paper, in order to produce efficient and low cost hydrogen by using alternative energies with simple ways; a photocatalytic electrocatalytic dual hydrogen production system (PEHPS) which combined discontinuous photocatalytic and electrocatalytic systems in one continuous dual system was designed and optimized. In the photocatalytic chamber of PEHPS, nano-sized Cd(1-x)ZnxS/Pt photocatalysts were utilized. The synthesized Cd(1-x)ZnxS/Pt photocatalysts were characterized with scanning electron microscopy (SEM), X-Ray Diffraction (XRD) and diffuse reflectance UV Vis spectroscopy. The most active photocatalyst having CdZnS2 core and 10% Pt shell showed 24.0 mLg(-1) h(-1) (963.6 gmol g 1 h(-1)) hydrogen evolution rate with 4.01% solar energy conversion efficiency (SECE%). S2O3-2 produced in the photocatalytic chamber of PEHPS was used as redox species in the electrocatalytic chamber. This process decreased the cell potential of water electrolysis from 2.50 V to 1.70 V on glassy carbon electrodes. Moreover, usage of electro-polymerized metallophthalocyanines (Poly-MPc) as cathode active electrocatalyst, the over-potential of cathode of the electrocatalytic chamber for hydrogen reduction reaction decreased by 0.230 V. (C) 2015 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    A new sulfur source for the preparation of efficient Cd(1-x)ZnxS photocatalyst for hydrogen evolution reaction
    (PERGAMON-ELSEVIER SCIENCE LTD, 2018) KOCA, ATIF; Agopcan, Burag; Akyuz, Duygu; Karaca, Fatma; Sarioglu, Cevat; Koca, Atif
    Cd(1-x)ZnxS hexagonal crystals were for the first time synthesized via thermal sulfurization of Cd(1-x)ZnxO particles by using the elemental sulfur as the sulfur source. A temperature profile in the tube furnace was designed to obtain the proposed particle size, crystal structure, and morphology. Synthesized Cd(1-x)ZnxS particles were characterized with scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Raman spectroscopy, and diffuse reflectance UV Vis spectroscopy. It was seen that there was a polynomial relationship between the band gap and Cd: Zn ratio in the Cd(1-x)ZnxS. Cd0.58Zn023S has shapeless particles between 250 and 500 nm particle size. It was observed that particle size decreased as Zn ratio increased in the Cd(1-x),ZnxS. Cd(1-x),ZnxS hexagonal crystals had nano step surfaces which were one of the desired factors for achieving high photocatalytic efficiency. Finally, Synthesized Cd(1-x.)ZnxS particles were used as photocatalysts for the photocatalytic hydrogen evolution reaction (HER). Cd0.77Zn0.23S structure behaved the most active one among the different compositions of Cd(1-x)ZnxS nanoparticles. Cd0.77Zn0.23S showed almost high photocatalytic activity for HER with 1927 mu mol g(-1) h(-1) hydrogen evolution rate without using noble co-catalyst such as platinum. This good photocatalytic activity was believed to be due to the nanostep surface structure Cd0.77Zn0.23S which led the separation of the reduction and oxidation reaction sites and inhibited the recombination of the generated electrons and holes. Observation of considerably high photocurrent and open circuit potentials and changes in the electrochemical impedance spectroscopy responses supported the photocatalytic activity of the Cd0.77Zn0.23S particles. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.