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    Öğe
    Nanoporous Pd-Cu-Si Amorphous Thin Films for Electrochemical Hydrogen Storage and Sensing
    (Amer Chemical Soc, 2021) Sarac, Baran; Karazehir, Tolga; Yuce, Eray; Muehlbacher, Marlene; Sarac, A. Sezai; Eckert, Juergen
    Increasing the efficiency of hydrogen storage and release using recent generation metallic glass nanofilms (MGNFs) offers green solutions for nanoscale energy applications. Contrary to flat nanofilms, enhanced electrochemical performance of Pd-Cu-Si MGNF assemblies for hydrogen interaction is obtained on different sizes and configurations of a nanoporous alumina support. In particular, 10 nm thick samples with pore diameters of 25 nm reach a high specific pseudocapacitance per unit mass of 637 F g(-1), which is more than an order of magnitude larger than for flat samples, surpassing the precious metal-based systems in the literature. The same electrode exhibits the highest double-layer capacitance calculated from the equivalent circuit model of the electrochemical impedance spectra, featuring its eligibility for hydrogen nanosensors. A rough and fully coated surface is attained for samples of 250 mu m thickness and above, while smoother and open-pore structures are observed for lower thicknesses, inducing a capillary pressure and turbulent flow effect for the latter case. The comparison of cyclic voltammetry (CV) profiles recorded in the region where hydrogen-metal interactions occur confirms a remarkable desorption charge difference, reaching 2.5 times higher values for the 50 nm thick 25 nm pore diameter than the 40 nm pore diameter and flat electrodes, and lower absolute impedance values near-DC range revealing their highly conductive behavior.
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    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.