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    Co-catalyst-free photocatalytic hydrogen evolution by Laponite D clay
    (ELSEVIER SCIENCE SA, 2020) Aslan, Emre.
    Laponite D is known as a zwitterionic synthetic clay having disc-shaped with negatively charged top faces and positively charged lateral edges, which is photochemically inactive and used to increase catalytic active surfaces. Herein, photocatalytic hydrogen evolution over Laponite D, which known as low cost inorganic clay, is firstly reported in a system containing Eosin-Y (EY) and triethanolamine (TEOA) as a photosensitizer and electron donor, respectively, under visible light illumination. This reaction system shows excellent stability due to the good charge transport and separation efficiency thanks to zwitterionic property of Laponite D.
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    Donor-pi-acceptor dye-sensitized photoelectrochemical and photocatalytic hydrogen evolution by using Cu2WS4 co-catalyst
    (PERGAMON-ELSEVIER SCIENCE LTD, 2019) Patir, Imren Hatay.; Aslan, Emre.; Yanalak, Gizem.; Karaman, Merve.; Sarilmaz, Adem.; Can, Mumin.; Can, Mustafa.; Ozel, Faruk.
    Photoelectrochemical and photocatalytic hydrogen evolution reaction (HER) have been investigated by using metal free donor-acceptor (D-A) and donor-pi-acceptor (D-pi-A) dyes, which are abbreviated as MC-32 and MC-048, respectively, sensitized TiO2 as a photo-catalyst with or without Cu2WS4 co-catalyst. This co-catalyst is synthesized by a low-cost and simple hot injection method, under visible light illumination. The photoactivities of these dyes have been clarified according to their structural, optical and electrochemical properties. Photocatalytic activities have been slightly increased when added the Cu2WS4 co-catalyst (dye/TiO2/Cu2WS4). This catalytic activity is also compared to that of noble metal Pt (dye/TiO2/Pt). It has been found that 121 mu molg(-1)h(-1), 179 mu molg(-1)h(-1), 348 mu molg(-1)h(-1), 212 mu molg(-1)h(-1), 422 mu molg(-1)h(-1) and 1139 mu molg(-1)h(-1) hydrogen have been evolved by using MC-32/TiO2, MC-32/TiO2/Cu2WS4, MC-32/TiO2/Pt, MC-048/TiO2, MC-048/TiO2/Cu2WS4 and MC-048/TiO2/Pt, respectively. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
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    The investigation of novel D-pi-A type dyes (MK-3 and MK-4) for visible light driven photochemical hydrogen evolution
    (ELSEVIER SCI LTD, 2019) Aslan, Emre.; Karaman, Merve.; Yanalak, Gizem.; Can, Mustafa.; Ozel, Faruk.; Patir, Imren Hatay.
    Two novel donor-n-acceptor (D-pi-A) semiconductor organic dyes have been synthesized for the photochemical hydrogen evolution reaction (HER) to sensitize TiO2 for the first time. The molecular structures of D-pi-A semiconductor organic dyes, which are entitled as MK-3 and MK-4, have been characterized by NMR spectroscopy method; and also electrochemical and optical properties have been investigated by cyclic voltammetry and UV-Vis absorption techniques, respectively. Amount of dye loading on TiO2 surface has been investigated by EDX method. The HER activities have been explored in the presence of triethanolamine (TEOA) as a electron donor reagent under sunlight (solar simulator illumination limited by cut-off filter lambda >= 420 nm) in the absence and presence of co-catalysts (Pt and Cu2WS4). Transient photocurrent densities of MK-3/TiO2 and MK-4/TiO2 electrodes have been reached to 110 mu A cm(-1) and 275 mu A cm(-1), respectively. The photocatalytic HER activities have been relatively enhanced in the presence of the Pt or Cu2WS4 co-catalysts (dye/TiO2/Cu2WS4 or dye/TiO2/Pt) when compared to only dye/TiO2. The HER rates have been found as 427, 1277, 675, 682, 1027 and 795 mu molg(-1) h(-1) for the MK-3/TiO2, MK-3/TiO2 /Pt, MK-3/TiO2/Cu2WS4, MK-4/TiO2, MK-4/TiO2/Pt and MK4/TiO2/Cu2WS4 , respectively. The differences of photochemical activities of MK-3/TiO2 and MK-4/TiO2 have been stated taking into account dye molecule structures. Moreover, the HER mechanism have been described by using electrochemical band energy levels of dyes, TiO2 and Cu2WS4 co-catalyst.
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    Synthesis of novel tetrazine based D-pi-A organic dyes for photoelectrochemical and photocatalytic hydrogen evolution
    (ELSEVIER SCIENCE SA, 2020) Aslan, Emre.; Karaman, Merve.; Yanalak, Gizem.; Bilgili, Hakan.; Can, Mustafa.; Ozel, Faruk.; Patir, Imren Hatay.
    Two novel donor-pi-acceptor (D-pi-A) dyes, called as MK-2 and MK-8, are synthesized. Their structural, optical and electrochemical properties are investigated by NMR, absorption/photoluminescence spectroscopies and cyclic voltammetry techniques, respectively. Photocatalytic and photoelectrochemical hydrogen evolution properties of these D-pi-A dyes are explored by using triethanolamine (TEOA) as a sacrificial electron donor under anaerobic conditions and visible light irradiation with or without co-catalysts (Cu2WS4 and Pt) for the first time. Photoelectrochemical and photocatalytic hydrogen evolution reaction (HER) activities of these dyes are studied by using TiO2 coated FTO electrodes and powdered TiO2 (Degussa P25), respectively. Photoelectrochemical response of MK-2/TiO2 and MK-8/TiO2 are figured out in the order of 180 mu A cm(-1) and 80 A cm(-1). The photocatalytic hydrogen evolution amounts of MK-2/TiO2, MK-2/TiO2/Cu2WS4, MK-2/TiO2/Pt, MK-8/TiO2, MK-8/TiO2/Cu2WS4 and MK-8/TiO2/Pt are turned out to be 565, 920, 1828, 374, 522 and 1260 mu molg(-1) h(-1), respectively. Dye/TiO2 photocatalysts are displayed good stability in the both photochemical HER experiments. The alteration in the HER activities of MK-2 and MK-8 is explained by molecule structures of dyes. The proposed mechanism of photocatalytic hydrogen evolution is clarified by using electrochemical band levels of each constituent.