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    Enhanced photoelectrochemical activity of magnetically modified TiO2 prepared by a simple ex-situ route
    (Springer, 2022) Kuyumcu, Ozge Kerkez; Bayazit, Sahika Sena; Akyuz, Duygu; Koca, Atif; N/A; N/A; Yılmaz, Seda; PhD Student; PhD Student; N/A; N/A; N/A; N/A
    Modified TiO2 nanocomposites have been recognized as attractive photocatalytic materials in solar energy conversion. The aim of this study is to enhance the photoelectrochemical performance under visible light region by magnetically modified TiO2 nanocomposites (Fe3O4/TiO2 and NiFe2O4/TiO2) prepared by a simple ex-situ non-thermal route. The magnetic TiO2 nanocomposites were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectra (DRS), photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), vibrational scanning magnetometry (VSM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). Photoelectrochemical analysis was performed; chronoamperometry and Mott-Schottky curves were obtained. Results indicated that these non-noble, low-cost photocatalysts have shown the desired features; NiFe2O4/TiO2 have a suitable band gap to harvest visible range of solar light; they have reduced electron-hole recombination; and it is magnetically separable from reaction media. The most promising nanocomposite was found as NiFe2O4/TiO2 with a maximum photocurrent density 132 mu A cm(-2). The possible mechanism accounting for the improved photoelectrochemical performance of NiFe2O4/TiO2 is proposed.
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    Sonochemical synthesis and electrochemical characterization of alpha-nickel hydroxide: precursor effects
    (Springer, 2013) N/A; N/A; Department of Chemistry; N/A; Ertaş, Fatma Sinem; Kaş, Recep; Ünal, Uğur; Birer, Özgür; Master Student; Master Student; Faculty Member; Researcher; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; N/A; N/A; N/A; 42079; N/A
    Sonochemical degradation of urea was employed to synthesize alpha-nickel hydroxide from different nickel salts. Utilization of ultrasound yielded products with properties significantly different than the products obtained by thermal degradation of urea. the effect of intercalating chloride, nitrate, Acetate, and sulfate anions on morphology and electrochemical performance was studied. the sulfate-intercalated sample had the smallest interlayer spacing when obtained by the sonochemical method, contradicting all the previous thermal synthesis results. the specific capacitance trend also differed from the literature values, and the value for the sulfate-intercalated sample was larger than that of acetate-and nitrate-intercalated samples. Ultrasonic synthesis increased the specific capacitance of the sulfate-intercalated sample significantly. This sample was also the most reversible and had the highest charge efficiency.
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    Surface modified TiO2/reduced graphite oxide nanocomposite anodes for lithium ion batteries
    (Springer, 2020) Slabon, Adam; Afyon, Semih; Department of Chemistry; Department of Chemistry; N/A; Subaşı, Yaprak; Somer, Mehmet Suat; Yağcı, Mustafa Barış; Researcher; Faculty Member; Researcher; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; College of Sciences; N/A; N/A; 178882; N/A
    Anatase TiO2 nanoparticles with an average crystallite size of ~ 20 nm are synthesized through a sol-gel method. A composite anode for Li-ion batteries is prepared with the synthesized TiO2 nanoparticles and reduced graphite oxide (RGO) as the conductive carbon source. After the preparation of TiO2/RGO nanocomposite, a novel surface modification is carried out by the employment of H2O2 to enhance the overall electrochemical performance of nanocomposite anode (TiO2/RGO-P composite). The physical and chemical characterizations of the surface modified TiO2/RGO-P composites are performed with X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM) analyses. The electrochemical performance of TiO2/RGO-P composite electrodes is investigated via galvanostatic charge-discharge cycling tests in a potential window of 1.0-3.0 V. Compared to the plain TiO2/RGO composite anode, the TiO2/RGO-P composite anode has higher reversible capacities and better cycling performance due to the enhanced and stable formation of 3D channels of TiO2 nanoparticles with RGO stemming from the surface modification with H2O2. The TiO2/RGO-P composite anode delivers reversible discharge capacities around 291 mA h g(-1) at a rate of 100 mA g(-1), whereas the value stays at 214 and 143 mA h g(-1) for the plain TiO2/RGO composite and TiO2 nanoparticle without any RGO, respectively.