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    Peripherally and non-peripherally carboxylic acid substituted Cu(ii) phthalocyanine/reduced graphene oxide nanohybrids for hydrogen evolution reaction catalysts
    (Royal Soc Chemistry, 2023) Kaplan, Ekrem; Karazehir, Tolga; Gumrukcu, Selin; Sarac, Baran; Sarac, A. Sezai; Hamuryudan, Esin
    Due to growing environmental concerns and increasing energy needs, hydrogen, one of the key options as a future energy carrier, has lately gained more interest. In this study, we have reported nanohybrid electrocatalyst materials based on peripherally and non-peripherally carboxylic acid substituted copper phthalocyanines (CuPcs) and reduced graphene oxide (rGO) constructed via pi-pi interactions between CuPcs and rGO. Prepared nanocomposites were coated onto the surface of a glassy carbon electrode and their electrocatalytic activity for the hydrogen evolution reaction (HER) was studied. Structural, electrochemical, and surface morphological properties of the produced electrodes were investigated using Fourier transform infrared (FT-IR) and Raman spectroscopy, X-ray diffraction (XRD), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and scanning electron microscopy (SEM) analyses. Electrochemical measurements indicated that the peripherally substituted rGO/CuPc electrodes have more efficiency and activity compared to the non-peripherally substituted ones. In addition, the EIS results show that peripherally carboxylic substituted rGO/CuPc electrodes become more conductive due to the position and content of the carboxyl groups. This increasing performance of the HER implied by a smaller impedance together with more facile electron transfer kinetics indicates a pronounced enhancement of the electrocatalytic hydrogen activity of peripherally carboxylic substituted rGO/CuPc electrodes.
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    Öğe
    Reduced graphene oxide supported meso-pyridyl BODIPY-Cobaloxime complexes for electrocatalytic hydrogen evolution reaction
    (Pergamon-Elsevier Science Ltd, 2024) Gumrukcu, Selin; Kaplan, Ekrem; Karazehir, Tolga; Ozcesmeci, Mukaddes; Ozcesmeci, Ibrahim; Hamuryudan, Esin
    Creating innovative catalysts utilizing nonprecious metals for the electrocatalytic hydrogen evolution reaction (HER) poses a significant difficulty. We present a cobaloxime (Cox) complex having pyridine (2-Cox) and tetrafluorophenyl-thio-pyridine (4-Cox) functional groups, which contains a 4,4-Difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) moiety. This combination serves as a catalyst for proton reduction and is immobilized onto reduced graphene oxide (rGO) by pi-pi stacking between the cobaloxime complex and rGO. Moreover, the unique complex's structures were determined through the application of ultraviolet-visible spectroscopy (UV-Vis), Fourier Transform Infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), and scanning electron microscopy (SEM). The electrocatalytic activity of the two rGO/2-Cox and rGO/4-Cox electrodes towards hydrogen (H-2) were examined under both alkaline and acidic conditions. The cobaloxime-modified rGO electrodes demonstrate superior electrocatalytic performance for the HER under acidic conditions compared to alkaline conditions. The overpotential at a current density of 10 mA cm(-2) for rGO/2-Cox in 0.5 M H2SO4 is -0.342 V, which is notably lower than the overpotential of rGO/4-Cox (-0.496 V). The Tafel slope for the rGO/2-Cox electrode in a 0.5 M H2SO4 solution is 111 mV.dec(-1), but for the rGO/4-Cox electrode it is 156 mVdec(-1). This discrepancy suggests that the rGO/2-Cox electrode demonstrates better performance in the HER compared to the rGO/4-Cox electrode.