Yazar "Gumrukcu, Selin" seçeneğine göre listele

Listeleniyor 1 - 7 / 7
  • [ X ]
    Öğe
    Functionalized highly electron-rich redox-active electropolymerized 3,4-propylenedioxythiophenes as precursors and targets for bioelectronics and supercapacitors
    (Royal Soc Chemistry, 2021) Karazehir, Tolga; Sarac, Baran; Gilsing, Hans-Detlev; Gumrukcu, Selin; Eckert, Jurgen; Sarac, A. Sezai
    In order to combine capacitive properties with processability, e.g. solubility in organic solvents, poly(3,4-propylenedioxythiophene) derivatives containing different functional groups like oxyphenyl methanol (-OPhCH2OH), oxybenzyl (-OBz), bromide (-Br) and tosyl (-OTs) were synthesized and electropolymerized as thin films from acetonitrile (ACN) using Et4NBF4 as an electrolyte. Multifunctionality in the substitution pattern of the polymer exhibits a similar trend between monomer oxidation potentials and specific capacitance (C-sp) vs. crystal size. The presence of pi-pi stacking interactions in the polymer structures plays an important role in building the crystal structures. The same order of flat band potential and C-sp values are observed for -OBz < -Br < -OTs < -OPhCH2OH substitutions. The structures of PProDOT-OBz and PProDOT-OPhCH2OH resemble each other much more than those of PProDOT-Br and PProDOT-OTs. Impedance measurements were conducted at different applied biases in order to define a Mott-Schottky analysis revealing the dependence of the semiconducting properties on the type of substituent present in the PProDOT derivative.
  • [ X ]
    Öğe
    Investigation of Electrocatalytic Hydrogen Evolution Reaction (HER) Efficiencies of Phthalocyanines/Carbon-Boron Quantum Dots Nanoconjugates
    (Wiley-VCH GmbH, 2025) Karahan, Basak Gizem; Gumrukcu, Selin; Kaplan, Ekrem; Karazehir, Tolga; Unlu, Caner; Coskun, Ibrahim Yagiz; Ozcesmeci, Ibrahim
    We developed highly efficient electrocatalysts for hydrogen evolution through the noncovalent integration (via electrostatic and pi-pi interactions) of tetra-hydroxythioethyl-substituted metal-free (H2Pc) and cobalt(II) phthalocyanines (CoPc) with boron-doped carbon quantum dots (CBQdot). Incorporation of CBQdots greatly enhanced the molecular organization and uniformity of H2Pc and CoPc through strong interfacial interactions. pi-pi stacking, hydrogen bonding, and coordination between cobalt center and CBQdot surface groups led to well-ordered nanoconjugate systems. Raman analyses showed a decreased D/G ratio, particularly in CoPc/CBQdot, indicating defect passivation and improved interfacial ordering. SEM, EDX, and AFM results demonstrated reduced aggregation, smaller uniformly dispersed particles, and smoother, more continuous film morphologies. The hybrid CoPc/CBQD catalyst demonstrated exceptional HER activity in acidic media, significantly outperforming the CBQDots, H2Pc, and CoPc. Remarkably, the hybrid catalyst demonstrated superior hydrogen evolution reaction (HER) activity in acidic media, achieving a low overpotential of 434 mV at 10 mA cm-2 current density with a favorable Tafel slope of 124 mV dec-1. This enhanced performance originates from the synergistic pi-pi stacking interactions between the phthalocyanine core and the carbon quantum dots, which effectively modulates the catalyst's active surface area. Our findings present a technologically viable approach for developing noble-metal-free HER catalysts. The strategic design of these pi-pi stacked nanoconjugates offers a promising pathway for efficient hydrogen production, addressing both performance and cost considerations in renewable energy applications.
  • [ X ]
    Öğe
    Low-Symmetry Phthalocyanine Cobalt Bis(dicarbollide) Conjugate for Hydrogen Reduction
    (Wiley-V C H Verlag Gmbh, 2018) Nar, Ilgin; Atsay, Armagan; Gumrukcu, Selin; Karazehir, Tolga; Hamuryudan, Esin
    The synthesis and characterization of two new A(3)B type unsymmetrical zinc phthalocyanines, one bearing a hydroxyl group and the other bearing a cobalt bis(dicarbollide) unit, are reported here. The introduction of diethylaminophenoxy moieties to the phthalocyanine fragments yields outstanding solubilities in organic solvents, as well as providing electropolymerization on the surface of the electrode. These modified electrodes are found to be effective for the electrocatalytic reduction of hydrogen ions in acidic media. The enhanced hydrogen-evolution reaction (HER) performance for the bis(dicarballide)-functionalized phthalocyanine-modified electrode can be simultaneously observed. This is attributed to its redox-active metal center of cobalt bis(dicarbollide), creating a synergistic effect, to facilitate many more electrocatalytic active sites, resulting in improved HER performance. The catalyst shows an onset potential of 163 mV at a current density of 8.79 mu Acm(-2), and a Tafel slope as low as 28 mVdec(-1).
  • [ X ]
    Öğe
    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.
  • [ X ]
    Öğe
    Polyacrylonitrile nanofibers with hollow NiCu, Ni, and Cu nanospheres: Boosting electrocatalysis via enhanced interfacial charge transport and storage
    (Elsevier, 2026) Sarac, Baran; Karazehir, Tolga; Zadorozhnyy, Vladislav; Moskovskikh, Dmitry; Yermekova, Zhanna; Gumrukcu, Selin; Yuce, Eray; Sarac, A. Sezai
    Multifunctional catalytic materials combining polymers with nanoparticles (NPs) lie in advancing their long-term stability, scalability, and predictable performance under real-world operating conditions. In this study, polyacrylonitrile (PAN) nanofibers loaded with hollow nickel (Ni), copper (Cu), and nickel-copper (NiCu) nanoparticles were fabricated. X-ray diffraction confirmed crystalline metal phases in the amorphous PAN matrix while indicating that similar to 25 % of Cu as CuO. Spectroscopic analysis revealed alterations in the nitrile and aliphatic stretching bands resulting from NP incorporation. Cu/PAN exhibited a more than twofold increase in the -C-H to -CN bond area, attributed to oxygen-containing functional groups from CuO formation. UV-Vis spectra demonstrated tunable absorbance: NiCu/PAN exhibited the broadest and most intense absorption across 250-500 nm, reflecting strong plasmonic coupling between alloyed particles. Electron microscopy illustrated uniform dispersion of NPs on PAN surface, with all three nanofibers showing continuous and bead-free morphology, while NiCu composites displayed reduced NP agglomeration compared to monometallic counterparts. Electrochemical impedance spectroscopy in 0.1 M LiClO4/ACN highlighted that NiCu/PAN possessed the lowest charge transfer resistance (R-ct approximate to 9.13 x 10(2) Omega cm(2)) and highest double-layer capacitance (C-dl approximate to 43.6 mu F cm(-2)), surpassing Ni/PAN and Cu/PAN analogues. Furthermore, the smallest overpotential at 1 mA cm(-2) (-197 mV) and Tafel curve (similar to 286 mV dec(-1)) were obtained for NiCu/PAN in 1 M KOH. The main objective of this research was to demonstrate that bimetallic interactions in hollow NiCu particles synergistically enhance interfacial charge transport and storage, thereby showing how metal composition and PAN nanofiber integration can optimize polymer-based nanocomposites for energy and environmental applications.
  • [ X ]
    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.
  • [ X ]
    Öğe
    Surface-governed electrochemical hydrogenation in FeNi-based metallic glass
    (Elsevier, 2020) Sarac, Baran; Zadorozhnyy, Vladislav; Ivanov, Yurii P.; Kvaratskheliya, Askar; Ketov, Sergey; Karazehir, Tolga; Gumrukcu, Selin
    The hydrogenation and oxide formation behavior of Fe-Ni-based metallic glasses (MGs), where measurements by the conventional gas-solid reaction method are difficult, is analyzed by a two-step approach: chronoamperometry followed by cyclic voltammetry (CA + CV). We introduce a concept of effective volume by measuring the thickness of the region where the hydrogen and hydroxyl ion interactions with Fe-based MG take place, which is characterized by high-angle annular dark-field scanning transmission electron microscopy. A very constant film thickness influenced by the OH- and H+ is confirmed by TEM, where the chemical homogeneity is maintained within this region. The weight percent of hydrogen and the corresponding hydrogen-to-metal ratio are determined as 1.16% and 0.56, respectively. When compared to previous studies conducted by the electrochemical- permeation method, the H/M ratio is found to be an order of magnitude larger. Electrochemical impedance spectroscopy (EIS) and subsequent equivalent circuit modeling (ECM) of the tested ribbons resolve the surface-diffusion processes for hydride formation and oxidation kinetics. This contribution provides a different perspective for the design and study of low-cost and high-performance amorphous nanofilms for hydrogenenergy applications, particularly when the common gas-adsorption methods are problematic.