Browsing by Author "Duran, Boris"

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    CVD Growth of Hematite Thin Films for Photoelectrochemical Water Splitting: Effect of Precursor-Substrate Distance on Their Final Properties
    (2023) Fernandez-Izquierdo, Leunam; Spera, Enzo Luigi; Duran, Boris; Marotti, Ricardo Enrique; Dalchiele, Enrique Ariel; del Rio, Rodrigo; Hevia, Samuel A.
    The development of photoelectrode materials for efficient water splitting using solar energy is a crucial research topic for green hydrogen production. These materials need to be abundant, fabricated on a large scale, and at low cost. In this context, hematite is a promising material that has been widely studied. However, it is a huge challenge to achieve high-efficiency performance as a photoelectrode in water splitting. This paper reports a study of chemical vapor deposition (CVD) growth of hematite nanocrystalline thin films on fluorine-doped tin oxide as a photoanode for photoelectrochemical water splitting, with a particular focus on the effect of the precursor-substrate distance in the CVD system. A full morphological, structural, and optical characterization of hematite nanocrystalline thin films was performed, revealing that no change occurred in the structure of the films as a function of the previously mentioned distance. However, it was found that the thickness of the hematite film, which is a critical parameter in the photoelectrochemical performance, linearly depends on the precursor-substrate distance; however, the electrochemical response exhibits a nonmonotonic behavior. A maximum photocurrent value close to 2.5 mA/cm(2) was obtained for a film with a thickness of around 220 nm under solar irradiation.
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    Enhanced photoconversion efficiency of hybrid TiO2/nox-MWCNT/Si photoanode for water splitting in neutral medium
    (2021) Olivares, Fernanda; Segura del Rio, Rodrigo; Reyes, Javier; Peon, Francisco; Henriquez, Ricardo; Hevia, Samuel A.; Duran, Boris; Villalonga, Reynaldo
    Hybrid films composed by TiO2 and functionalized MWCNTs were synthesized and used as photoanodes to perform the water splitting process under neutral and free of sacrificial agents medium. The results show that introducing a sublayer of MWCNTs functionalized with -NO2 and -COOH groups leads to structural modifications on TiO2 that decrease the band gap and reduce the recombination phenomenon. Those groups anchored to nanotubes also play an important role in their dispersibility and provide an additional electron withdrawing effect to the pristine nanotubes. These conditions significantly improve the photoconversion efficiency of the hybrid system until 15-fold regarding pristine TiO2 prepared under the same conditions. (c) 2020 Elsevier B.V. All rights reserved.
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    In Situ Synthesis of CuO/Cu2O Nanoparticle-Coating Nanoporous Alumina Membranes with Photocatalytic Activity under Visible Light Radiation
    (2023) Duran, Boris; Saldias, Cesar; Villarroel, Roberto; Hevia, Samuel A. A.
    We report the synthesis and characterization of CuO/Cu2O film supported on nanoporous alumina membranes (NAMs) and the photocatalytic properties in the removal of the organic pollutant methyl orange (MO). For this purpose, transparent nanostructured membranes were fabricated and sequentially modified with APTS ((3-aminopropyl)-trimethoxysilane) and EDTAD (ethylenediaminetetraacetic dianhydride) to form a highly functionalized surface with high density of carboxyl groups, which easily complex with copper cations. The Cu2+-modified membranes were annealed in a chemical vapor deposition (CVD) furnace to form a well-ordered nanostructured coating of CuO/Cu2O with photocatalytic properties. These modifications were followed by characterization with FT-IR and UV-visible spectra, X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), and energy dispersive X-ray spectroscopy (EDS). Finally, the photocatalytic performance of the NAM-CuO/Cu2O nanostructured membranes was tested in the aqueous removal of MO dye as a model reaction system. Our results revealed 50% photocatalytic removal of MO under continuous light irradiation for 2 h. The procedure presented in this work provides an adequate approach for the fabrication of nanostructured devices with photocatalytic properties for the degradation of organic compounds.
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    Nickel Nanopillar Arrays Electrodeposited on Silicon Substrates Using Porous Alumina Templates
    (2020) Bejide, Matias; Contreras, Patricio; Homm, Pia; Duran, Boris; Garcia-Merino, Jose Antonio; Rosenkranz, Andreas; Denardin, Juliano C.; del Rio, Rodrigo; Hevia, Samuel A.
    Nickel nanopillar arrays were electrodeposited onto silicon substrates using porous alumina membranes as a template. The characterization of the samples was done by scanning electron microscopy, X-ray diffraction, and alternating force gradient magnetometry. Ni nanostructures were directly grown on Si by galvanostatic and potentiostatic electrodeposition techniques in three remarkable charge transfer configurations. Differences in the growth mechanisms of the nanopillars were observed, depending on the deposition method. A high correlation between the height of the nanopillars and the charge synthesis was observed irrespective of the electrochemical technique. The magnetization measurements demonstrated a main dependence with the height of the nanopillars. The synthesis of Ni nanosystems with a controllable aspect ratio provides an effective way to produce well-ordered networks for wide scientific applications.