The electroformation and electroreduction of anodic films formed on silver in 0.1 M sodium hydroxide in the potential range of the Ag/Ag2O couple

The complex electrochemical reactions related to the electroformation and electroreduction of silver(I) oxide films in base electrolyte were investigated by means of combined potentiodynamic techniques and potential steps. The anodic process involves the initial fast OH− ion discharge yielding OH-adsorbed species and later continues to form the silver(I) oxide layer. The latter behaves as a duplex structure anodic layer with a degree of hydration changing with depth. The electroreduction characteristics of the anodic film depend both on potential sweep and anodic charge, and the relationships of the corresponding kinetic parameters fit qualitatively with those predicted by nucleation and growth mechanisms. Activity increases of silver caused by the potential sweeps are interpreted by the simultaneous contribution of the increase in the concentration of silver active surface sites and the change in size distribution of silver electrodeposited from silver(I) oxide.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

The electroformation and electroreduction of anodic films formed on silver in 0.1 M sodium hydroxide in the potential range of the Ag/Ag2O couple

The complex electrochemical reactions related to the electroformation and electroreduction of silver(I) oxide films in base electrolyte were investigated by means of combined potentiodynamic techniques and potential steps. The anodic process involves the initial fast OH− ion discharge yielding OH-adsorbed species and later continues to form the silver(I) oxide layer. The latter behaves as a duplex structure anodic layer with a degree of hydration changing with depth. The electroreduction characteristics of the anodic film depend both on potential sweep and anodic charge, and the relationships of the corresponding kinetic parameters fit qualitatively with those predicted by nucleation and growth mechanisms. Activity increases of silver caused by the potential sweeps are interpreted by the simultaneous contribution of the increase in the concentration of silver active surface sites and the change in size distribution of silver electrodeposited from silver(I) oxide.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Complex potentiodynamic response of silver in alkaline Electrolytes in the potential range of the Ag/Ag2O Couple

The potentiodynamic behaviour of Ag in 0.1 M NaOH in the potential range of Ag2O electroformation is investigated through the application of different potential/time perturbation programmes. The splitting of the electroreduction profile which is produced under well-defined perturbation conditions and the shift of the Ag2O electroreduction E/i profile under a constant charge condition, suggest that ageing-type processes are involved in the overall electrochemical reaction. These processes are related to a probable dehydration of the Ag2O multilayer.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

The electroformation and electroreduction of anodic films formed on silver in 0.1 M sodium hydroxide in the potential range of the Ag/Ag2O couple

The complex electrochemical reactions related to the electroformation and electroreduction of silver(I) oxide films in base electrolyte were investigated by means of combined potentiodynamic techniques and potential steps. The anodic process involves the initial fast OH− ion discharge yielding OH-adsorbed species and later continues to form the silver(I) oxide layer. The latter behaves as a duplex structure anodic layer with a degree of hydration changing with depth. The electroreduction characteristics of the anodic film depend both on potential sweep and anodic charge, and the relationships of the corresponding kinetic parameters fit qualitatively with those predicted by nucleation and growth mechanisms. Activity increases of silver caused by the potential sweeps are interpreted by the simultaneous contribution of the increase in the concentration of silver active surface sites and the change in size distribution of silver electrodeposited from silver(I) oxide.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Complex potentiodynamic response of silver in alkaline Electrolytes in the potential range of the Ag/Ag2O Couple

The potentiodynamic behaviour of Ag in 0.1 M NaOH in the potential range of Ag2O electroformation is investigated through the application of different potential/time perturbation programmes. The splitting of the electroreduction profile which is produced under well-defined perturbation conditions and the shift of the Ag2O electroreduction E/i profile under a constant charge condition, suggest that ageing-type processes are involved in the overall electrochemical reaction. These processes are related to a probable dehydration of the Ag2O multilayer.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

The keys to avoid undesired structural defects in nanotubular TiO2 films prepared by electrochemical anodization

The effect of the viscosity of solvent mixtures based in ethylene glycol on the formation of undesired structural defects (nanograss) during the electrochemical synthesis of nanotubular TiO2 structures is analyzed. High quality nanotubular TiO2 films can be achieved by diminishing the viscosity of ethylene glycol-based media by increasing the water content as well as using ethanol as additive. High surface tension of water also promotes the film fracture and accumulation of agglomerates on the film surface. A previously unexplored one-step strategy consisting in the addition of ethanol to ethylene glycol/water mixtures as an alternative anodization medium is proposed. The evidence obtained indicate that this medium allows obtaining nanotubular TiO2 films with superior structural stability against capillary forces during the film drying, avoiding the use of time consuming post-treatments such as the commonly employed supercritical CO2 dehydrating, improving the properties of the obtained nanomaterials.Fil: Broens, Martin Ignacio. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Ramos Cervantes, Wilkendry. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Oyarzún Jerez, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Universidad Tecnologica Metropolitana (utem); ChileFil: Lopez Teijelo, Manuel. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Linarez Pérez, Omar Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin

Electrochemical and ellipsometric data related to the formation of soluble silver (I) during the potentiodynamic polarization of polycrystalline silver in basic solutions

Soluble Ag(I) species is formed in the early stages of voltammetric silver electrooxidation in 0.1 M NaOH and 0.1 M NaOH + 1 M NaClO4 solutions at 25°C, as demonstrated by the rotating ring-disc technique. This result allows a reasonable interpretation of ellipsometric data obtained for the anodization of silver under different voltammetric conditions. Correspondingly, two anodic layers of different optical constants are electroformed. The hydrous Ag(I) oxide layer behaves as a porous structure with an average thickness of about 2.5 times greater than that of the anhydrous oxide.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Ellipsometry of silver electrodes in base solutions under different potential controlled perturbation conditions

The ellipsometric and reflectance response at 5461 A of silver in 0.1 M NaOH at 25°C, is studied in the Ag(O)/Ag(I) potential range when the electrode has been subjected to different complex potentiodynamic perturbations. The optical response depends remarkably on the potential sweep rate, on the accumulated anodic charge and on the number of potential cycles. The data of the complex anodic film can he interpreted in terms of a single film model in two limiting cases defined, in,terms of the ancdic charge involved as thin and thick films, respectively: (i)for thin anodic films (Qa -2) nf = 1.50 -0.12 i and (ii) for thick anodic films (Qa -2) nf = 1.50 - 0.22 i. Time dependence of the optical parameters of both reformed silver and anodic film are shown. Optical results correlates with electrochemical data recently reported and arc discussed in terms of different degree of hydrations For each type of anodic filmInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Simple and rapid one-step electrochemical synthesis of nanogranular Cu2O films

In the present work, we report a simple experimental strategy for the one-step electrochemical synthesis of nanogranular Cu2O films by copper anodization in fluoride-containing ethylene glycol media. Microscopic exploration using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM), shows the formation of spherical shape grains with sizes ranging from 20 to 40 nm. Raman and X-Ray Photoemission Spectroscopy (XPS) results indicate that only CuI oxide is obtained. A band gap energy Eg=2.01 eV is estimated from UV–vis reflectance spectroscopy indicating that an indirect transition mechanism between semiconductor bands takes place. These evidences indicate that the present synthesis of nanogranular Cu2O films is a promising method for obtaining improved properties of materials for the design of photoelectronic devices.Fil: Oyarzún Jerez, Diego Patricio. Universidad Andrés Bello; ChileFil: Broens, Martin Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Linarez Pérez, Omar Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Lopez Teijelo, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Islas, Rafael. Universidad Andrés Bello; ChileFil: Arratia-Perez, Ramiro. Universidad Andrés Bello; Chil

Oxide/hydroxide films on tin. II: Characterization of the anodic growth in alkaline solutions

The anodic growth of oxide/hydroxide films formed on tin in borate solutions (pH 8.9) has been studied. At potentials more positive than -0.2 V (SHE), oxide film growth occurs by an activation-controlled ionic condition under the influence of a high electric field across the film according to an exponential law as on valve metals. Optical properties of the anodic oxide films have been obtained by "in situ" ellipsometry. Tin oxide/hydroxide films are practically transparent and highly hydrated. Electrical properties of tin oxide layers have been obtained by electrochemical impedance spectroscopy. Impedance spectra are explained in terms of a simple physical model assuming that oxide layer behaves as an inhomogeneous single-layer film.Fil: Brunetti, Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; ArgentinaFil: Lopez Teijelo, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentin