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Papers by Silvina Fuentes
Revista Tecnología y Ciencia
El estudio de la interfase semiconductor/electrolito tiene aplicaciones en la producción de celda... more El estudio de la interfase semiconductor/electrolito tiene aplicaciones en la producción de celdas solares fotoelectroquímicas. Las propiedades semiconductoras de un semiconductor de tipo n pueden ser evaluadas mediante el modelo de Mott-Schottky cuando se lo pone en contacto con un electrolito. El titanio (Ti) es un metal que presenta una película de óxido espontánea, dióxido de titanio (TiO2), la cual puede ser crecida por anodización. En este trabajo se crecieron anódicamente películas de óxido de Ti, sobre los sustratos vidrio/Ti y chapa de Ti, y se aplicó el modelo de Mott-Schottky para evaluar sus propiedades semiconductoras en contacto con una solución de 0,5 M de HClO4 a temperatura ambiente. Bajo las condiciones descritas en este trabajo, los electrodos vidrio/Ti/TiO2 y chapa de Ti/TiO2 presentan el comportamiento de un semiconductor de tipo n con una concentración de donadores del orden de y , respectivamente. Las películas de óxido fueron estables antes y después de los ...
En este trabajo se presentan los resultados del estudio de la caracterización electroquímica de l... more En este trabajo se presentan los resultados del estudio de la caracterización electroquímica de las Decoraciones de Oro y Platino sobre Grafito Pirolitico Altamente Orientado (HOPG) como cátodos midiendo la actividad electrocatalítica con respecto a la reacción de desprendimiento de hidrógeno (RDH) en medio ácido. Se realizaron curvas corriente potencial (I vs V) obtenidas brought to you by CORE View metadata, citation and similar papers at core.ac.uk
The structure and properties of the electrochemical interface result from the interactions that o... more The structure and properties of the electrochemical interface result from the interactions that occur between the different components of an electrolytic solution and the metal electrode. In particular, the anion / metal interactions have been of great interest in recent years, mainly due to the development of new techniques that have allowed the study of in situ and ex situ tests of the characteristics of this chemical adsorption bond. Specifically adsorbed ions modify the charge distribution and the structure of the interface, affecting the processes that occur in this interface. Therefore the detailed knowledge of the anion / electrode interactions are extremely important, such as the electrochemical processes of corrosion, UPD and Electrocatalysis. This paper aims to analyze the tendency of synthesized nanostructured electrodes (Ag / HOPG) to adsorb anions, such as Cl- and Br-. The results indicate that the Ag nanostructures have the ability to adsorb anions, but the behavior is...
Matéria (Rio de Janeiro), 2018
RESUMEN La estructura y propiedades de la interfase electroquímica, son el resultado de las inter... more RESUMEN La estructura y propiedades de la interfase electroquímica, son el resultado de las interacciones que se producen entre los distintos componentes de una solución electrolítica y el electrodo metálico. En particular, las interacciones anión/metal han sido objeto de considerable interés en los últimos años gracias al desarrollo de nuevas técnicas que han permitido el estudio tanto “in-situ” como “ex-situ”, de las características de este enlace de adsorción. Los iones específicamente adsorbidos modifican la distribución de carga y la estructura de la interfase y consecuentemente influyen en los procesos que ocurren en ella. De allí que la comprensión de las interacciones anión/electrodo son de fundamental importancia en relación con procesos electroquímicos de relevancia tales como corrosión, UPD y Electrocatálisis. Este trabajo tiene como objetivo analizar la tendencia que presentan electrodos sintetizados nanoestructurados (Ag/HOPG) en adsorber aniones, como por ejemplo Cl- y...
Procedia Materials Science, 2015
New materials operating as future electrocatalysts into fuel cells or in environmental remediatio... more New materials operating as future electrocatalysts into fuel cells or in environmental remediation processes are continuously under research. Here we studied palladium modified electrodes, such as Pd/Ti and Pd/GC (glassy carbon), which are electrochemically built and used in chromate detection, in oxygen reduction and alcohols oxidation reaction. The palladium material electrodeposited at constant potential was characterized by X-ray diffraction, and scanning electron microscopy. The response of Pd/Ti nanoelectrodes, by oxygen reduction was observed in alkaline and acid supporting electrolytes. The diffusion coefficient of 2 10-5 cm 2 /s with a transference of 4ein 0.1M H 2 SO 4 solution was calculated. A higher coefficient value in 0.05 M NaOH was evaluated, because Ti substrate is also active in oxygen reduction in alkaline media. The reduction of Cr(VI) with Pd/Ti electrode proceeds at +0.58 V vs Ag/AgCl in H 2 SO 4 0.1M, with a diffusion coefficient of 2.210-5 0.01 cm 2 /s and a linear range between 0.019-0.69 mM Cr(VI). The lowest sensitivity 0.5 M Cr(VI) was determined with Pd/Ti electrode in the range permissible by drinking water of The oxidation of alcohol molecules in alkaline environment showed by Tafel curves, the activity order on Pd/Ti electrocatalyts is ethanol n-propanol >ethylene glycol. The calibration curve obtained by anodic peak current density of cyclic voltammetries upon an increasing alcohol concentration (3 to 90 mM alcohol) in NaOH 0.05 M, permitted to evaluate an activity of PdTi(+0.1V) PdTi(-0.3V)>PdTi(-0.9V). The performance of Pd/Ti electrocatalysts was better when compared with a modified Pd/GC electrocatalyst, in the studied reactions.
Procedia Materials Science, 2015
Palladium, has an unique property between the noble metals, that is the higher capacity to adsorb... more Palladium, has an unique property between the noble metals, that is the higher capacity to adsorb onto the surface, and within its network, the hydrogen, resulting the Pd of crucial importance to many industrial processes such as catalysis, fuel cell, hydrogen storage and metal brittlement. Since the activity of a noble metal deposited depends strongly on the surface structure, this work is focalized to study the Pd° nucleation and growth mechanisms onto different substrates such as HOPG, and thin pure titanium films. Thus, the constant potential method was used in the nanostructures formation varying the potentials and times. The resulting material was characterized electrochemically and morphologically using scanning electron microscopy (SEM), X-ray diffraction (XRD). In agreement with the results, the existing mechanism onto both substrates, was (3D) Pd ° instantaneous nucleation and growth controlled by diffusion, with a development of nanoparticles with defined morphology and narrow size distributions, which are potentially useful as electrocatalysts.
Tesis (Doctor en Fisica)--Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y F... more Tesis (Doctor en Fisica)--Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y Fisica, 2015.
Faraday Discuss., 2014
We have investigated the decoration of step-edges of HOPG by Ag, Au and Pt using experimental and... more We have investigated the decoration of step-edges of HOPG by Ag, Au and Pt using experimental and theoretical approaches. Metallic nanowires can be formed on bare or functionalized step-edges. Energy dispersion analysis indicates the presence of oxygenated groups. The experiments showed that nanowires can be obtained with the three metals along the step-edges, but the shapes and morphologies are very different. We have found that the interaction between the metal wires and the carbon follows the sequence: Pt > Au > Ag. The electronic redistribution between the atoms participating in the bond between the metallic nanowire and the step-edges shows a complicated pattern. The density of electronic states projected on the different atoms indicates that there are different orbitals participating in the bonds.
Revista Tecnología y Ciencia
El estudio de la interfase semiconductor/electrolito tiene aplicaciones en la producción de celda... more El estudio de la interfase semiconductor/electrolito tiene aplicaciones en la producción de celdas solares fotoelectroquímicas. Las propiedades semiconductoras de un semiconductor de tipo n pueden ser evaluadas mediante el modelo de Mott-Schottky cuando se lo pone en contacto con un electrolito. El titanio (Ti) es un metal que presenta una película de óxido espontánea, dióxido de titanio (TiO2), la cual puede ser crecida por anodización. En este trabajo se crecieron anódicamente películas de óxido de Ti, sobre los sustratos vidrio/Ti y chapa de Ti, y se aplicó el modelo de Mott-Schottky para evaluar sus propiedades semiconductoras en contacto con una solución de 0,5 M de HClO4 a temperatura ambiente. Bajo las condiciones descritas en este trabajo, los electrodos vidrio/Ti/TiO2 y chapa de Ti/TiO2 presentan el comportamiento de un semiconductor de tipo n con una concentración de donadores del orden de y , respectivamente. Las películas de óxido fueron estables antes y después de los ...
En este trabajo se presentan los resultados del estudio de la caracterización electroquímica de l... more En este trabajo se presentan los resultados del estudio de la caracterización electroquímica de las Decoraciones de Oro y Platino sobre Grafito Pirolitico Altamente Orientado (HOPG) como cátodos midiendo la actividad electrocatalítica con respecto a la reacción de desprendimiento de hidrógeno (RDH) en medio ácido. Se realizaron curvas corriente potencial (I vs V) obtenidas brought to you by CORE View metadata, citation and similar papers at core.ac.uk
The structure and properties of the electrochemical interface result from the interactions that o... more The structure and properties of the electrochemical interface result from the interactions that occur between the different components of an electrolytic solution and the metal electrode. In particular, the anion / metal interactions have been of great interest in recent years, mainly due to the development of new techniques that have allowed the study of in situ and ex situ tests of the characteristics of this chemical adsorption bond. Specifically adsorbed ions modify the charge distribution and the structure of the interface, affecting the processes that occur in this interface. Therefore the detailed knowledge of the anion / electrode interactions are extremely important, such as the electrochemical processes of corrosion, UPD and Electrocatalysis. This paper aims to analyze the tendency of synthesized nanostructured electrodes (Ag / HOPG) to adsorb anions, such as Cl- and Br-. The results indicate that the Ag nanostructures have the ability to adsorb anions, but the behavior is...
Matéria (Rio de Janeiro), 2018
RESUMEN La estructura y propiedades de la interfase electroquímica, son el resultado de las inter... more RESUMEN La estructura y propiedades de la interfase electroquímica, son el resultado de las interacciones que se producen entre los distintos componentes de una solución electrolítica y el electrodo metálico. En particular, las interacciones anión/metal han sido objeto de considerable interés en los últimos años gracias al desarrollo de nuevas técnicas que han permitido el estudio tanto “in-situ” como “ex-situ”, de las características de este enlace de adsorción. Los iones específicamente adsorbidos modifican la distribución de carga y la estructura de la interfase y consecuentemente influyen en los procesos que ocurren en ella. De allí que la comprensión de las interacciones anión/electrodo son de fundamental importancia en relación con procesos electroquímicos de relevancia tales como corrosión, UPD y Electrocatálisis. Este trabajo tiene como objetivo analizar la tendencia que presentan electrodos sintetizados nanoestructurados (Ag/HOPG) en adsorber aniones, como por ejemplo Cl- y...
Procedia Materials Science, 2015
New materials operating as future electrocatalysts into fuel cells or in environmental remediatio... more New materials operating as future electrocatalysts into fuel cells or in environmental remediation processes are continuously under research. Here we studied palladium modified electrodes, such as Pd/Ti and Pd/GC (glassy carbon), which are electrochemically built and used in chromate detection, in oxygen reduction and alcohols oxidation reaction. The palladium material electrodeposited at constant potential was characterized by X-ray diffraction, and scanning electron microscopy. The response of Pd/Ti nanoelectrodes, by oxygen reduction was observed in alkaline and acid supporting electrolytes. The diffusion coefficient of 2 10-5 cm 2 /s with a transference of 4ein 0.1M H 2 SO 4 solution was calculated. A higher coefficient value in 0.05 M NaOH was evaluated, because Ti substrate is also active in oxygen reduction in alkaline media. The reduction of Cr(VI) with Pd/Ti electrode proceeds at +0.58 V vs Ag/AgCl in H 2 SO 4 0.1M, with a diffusion coefficient of 2.210-5 0.01 cm 2 /s and a linear range between 0.019-0.69 mM Cr(VI). The lowest sensitivity 0.5 M Cr(VI) was determined with Pd/Ti electrode in the range permissible by drinking water of The oxidation of alcohol molecules in alkaline environment showed by Tafel curves, the activity order on Pd/Ti electrocatalyts is ethanol n-propanol >ethylene glycol. The calibration curve obtained by anodic peak current density of cyclic voltammetries upon an increasing alcohol concentration (3 to 90 mM alcohol) in NaOH 0.05 M, permitted to evaluate an activity of PdTi(+0.1V) PdTi(-0.3V)>PdTi(-0.9V). The performance of Pd/Ti electrocatalysts was better when compared with a modified Pd/GC electrocatalyst, in the studied reactions.
Procedia Materials Science, 2015
Palladium, has an unique property between the noble metals, that is the higher capacity to adsorb... more Palladium, has an unique property between the noble metals, that is the higher capacity to adsorb onto the surface, and within its network, the hydrogen, resulting the Pd of crucial importance to many industrial processes such as catalysis, fuel cell, hydrogen storage and metal brittlement. Since the activity of a noble metal deposited depends strongly on the surface structure, this work is focalized to study the Pd° nucleation and growth mechanisms onto different substrates such as HOPG, and thin pure titanium films. Thus, the constant potential method was used in the nanostructures formation varying the potentials and times. The resulting material was characterized electrochemically and morphologically using scanning electron microscopy (SEM), X-ray diffraction (XRD). In agreement with the results, the existing mechanism onto both substrates, was (3D) Pd ° instantaneous nucleation and growth controlled by diffusion, with a development of nanoparticles with defined morphology and narrow size distributions, which are potentially useful as electrocatalysts.
Tesis (Doctor en Fisica)--Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y F... more Tesis (Doctor en Fisica)--Universidad Nacional de Cordoba, Facultad de Matematica, Astronomia y Fisica, 2015.
Faraday Discuss., 2014
We have investigated the decoration of step-edges of HOPG by Ag, Au and Pt using experimental and... more We have investigated the decoration of step-edges of HOPG by Ag, Au and Pt using experimental and theoretical approaches. Metallic nanowires can be formed on bare or functionalized step-edges. Energy dispersion analysis indicates the presence of oxygenated groups. The experiments showed that nanowires can be obtained with the three metals along the step-edges, but the shapes and morphologies are very different. We have found that the interaction between the metal wires and the carbon follows the sequence: Pt > Au > Ag. The electronic redistribution between the atoms participating in the bond between the metallic nanowire and the step-edges shows a complicated pattern. The density of electronic states projected on the different atoms indicates that there are different orbitals participating in the bonds.