Browsing by Author "Lisoni, Judit"

Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    First approach of fractals nickel-copper dendrites on stainless steel electrodes for ammonia oxidation to nitrogen monitored in operando by differential electrochemical mass spectroscopy
    (2024) Matamala-Troncoso, Felipe; Diaz-Coello, Sergio; Martinez, Francisco; Barrientos, Herna; Lisoni, Judit; Armijo, Francisco; Lozano, David; Pizarro, Jaime; Arevalo, Maria del Carmen; Pastor, Elena; Aguirre, Maria Jesus
    Fractal nickel-copper dendrites were synthesized by electrochemical deposition (ECD) on a stainless steel electrode (SS/NiCu). The electrode surface was characterized using Field Emission Scanning Electron Microscopy (FE-SEM), X-ray diffractometry (XRD), and Raman spectroscopy. The Ni-Cu molar ratio and the time applied in the ECD method were studied, revealing that both are critical factors in modifying and controlling the surface morphology. The SS/NiCu electrodes show a higher density current response when exposed to ammonium hydroxide, reaching a limiting current density at concentrations above 0.050 M NH4OH. 4 OH. Ammonia oxidation reaction (AOR) was monitored in operando using differential electrochemical mass spectroscopy (DEMS). When a bias potential over +1.50 V (vs. RHE) was applied, the evolution of oxygen and NO was observed. However, N2 2 was the only oxidation product at a constant potential below +1.50 V (vs. RHE). Oxygen (O2) 2 ) evolution was the main competitive reaction during the AOR. The results show that products are strongly dependent on the electrochemical perturbation applied. The study demonstrated that the SS/NiCu electrodes are suitable for AOR to N2 2 in high alkaline conditions.
  • No Thumbnail Available
    Item
    High performance of V2O5 thin film electrodes for lithium-ion intercalation
    (2022) Hevia, Samuel A.; Orive, Joseba; Guzman, Fernando; Cisternas, Eduardo; Dietrich, Fabian; Villarroel, Roberto; Lisoni, Judit
    A reduced toxicity production route of vanadium pentoxide thin films together with the study of the fabrication parameters that allow optimizing the performance of this material as a cathode for lithium-ion batteries is presented. V2O5 films were fabricated on silicon and stainless-steel substrates by combining electron beam evaporation of metallic vanadium film followed by an oxidation process. A strong dependence on their performance as cathodes for LiBs to the film thickness and microstructure was found, the later depending mainly on the oxidation temperature. Particularly, V2O5 electrodes with 150 nm of thickness fabricated from 50 nm of metallic vanadium oxidized at 500 degrees C, exhibit excellent performance with a reversible and fast Li storage capability, a high average discharge capacity up to 271 mAh/g at 0.5C, very close to the theoretical capacity (294 mAh/g), with near to 100% of coulombic efficiency. First-principles calculations of Li+ diffusion in three main V2O5 crystallographic directions using density functional theory (DFT) were performed to explain how this remarkable performance is related to the film microstructure.
  • No Thumbnail Available
    Item
    In-situ hydrogenated V2O5 thin films: Study of the structural dynamics and their behavior as Li-ion batteries cathode
    (2024) Briceno, Mackarena; Villarroel, Roberto; Zambrano-Mera, Dario; Fernandez, Juan; Flores, Marcos; Rojas-Saez, Nicols; Lisoni, Judit; Hevia, Samuel; Espinoza-Gonzalez, Rodrigo
    This investigation focuses on a one-step preparation method to produce hydrogenated V2O5 thin films by controlling the atmosphere of the DC reactive magnetron sputtering process. An increasing hydrogen flux during the film deposition promotes the formation of defects such as oxygen vacancies and hydroxyl sites in the oxide matrix. The hydrogenated samples were tested as cathodes in Li-ion batteries and exhibited lower charge capacities but superior stability to cycling compared to pristine V2O5 film. These results pave the way to prepare hydrogenated transition metal oxide thin films by a simple route without further thermal procedures and affordable conditions.