Fernanda Trombetta | Universidade Federal do Rio Grande do Sul (original) (raw)
Uploads
Papers by Fernanda Trombetta
Electrochemical studies were performed using Ni electrodes in solutions of a mixture of ethylene ... more Electrochemical studies were performed using Ni electrodes in solutions of a mixture of ethylene glycol or of γ-butyrolactone with 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The aim of the study was to evaluate the use of these systems in electrochemical double-layer capacitor. Cyclic voltammetry experiments showed a potential range at which the Ni electrode behaved as a polarizable electrode. Ni oxidizes at high anodic potentials. Inside the potential range without electrochemical activity, the capacitance and the solution resistance, which were evaluated by impedance electrochemical spectroscopy, were compared for the two solutions tested. Conductivity measurements of the electrolytes with different compositions were also acquired. The results of cyclic voltammetry indicated that the Ni has a wide electrochemical window and low current peak densities of oxidation in the γ-butyrolactone medium than in ethylene glycol medium. The γ-butyrolactone and 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solutions had the highest conductivity values. Decreased 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid content in different solvent mixtures resulted in an increase in the capacitance value at the Ni/electrolyte interface. The highest capacitance values were obtained for Ni in ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate medium.
Journal of Applied Electrochemistry, 2009
This study compares two series of solvents for application in aluminum electrolytic capacitors: e... more This study compares two series of solvents for application in aluminum electrolytic capacitors: ethylene glycol (EG) and water mixtures, and ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) ionic liquid (IL) mixtures. Electrochemical impedance spectroscopy and cyclic voltammetry were carried out with a previously anodized aluminum disk electrode. Comparative measurements of solution resistance, polarization resistance, AC capacitance, and passive current were made. The results show that EG–IL mixtures with low amounts of IL (10% IL–90% EG v/v) have a low solution resistance. Low values of solution resistance, high values of polarization resistance, small passive current, and uniform capacitance of anodized aluminum in EG–IL mixtures are favorable properties of the BMI.BF4 IL for use as an electrolyte in the construction of electrolytic aluminum capacitors.
Corrosion Science, 2011
The stability of electrochemically passivity aluminium has been investigated in mixtures of ethyl... more The stability of electrochemically passivity aluminium has been investigated in mixtures of ethylene glycol, 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, Na2B4O7.10H2O and NaH2PO4. The effects of (i) borax and sodium dihydrogen phosphate salts presence, (ii) water absorption and (iii) ethylene glycol content are studied by electrochemical impedance spectroscopy (EIS). The results show a decrease in the polarization resistance and an increase in the capacitance associated with the passive oxide dielectric properties with an increase in the water and/or ethylene glycol content in the mixtures. The presence of Na2B4O7.10H2O and NaH2PO4 salts stabilize the oxide layer.► The Al anodic film is stable in BMI.BF4 ionic liquid. ► The solution resistance diminishes when ethylene glycol (EG) is added on BMI.BF4. ► The capacitance of Al anodic film increases in wet BMI.BF4 and EG mixtures. ► The Al anodic film resistance diminishes in wet BMI.BF4 and EG mixtures. ► Borate and phosphate stabilize the Al anodic film in wet electrolyte environment.
Electrochemical studies were performed using Ni electrodes in solutions of a mixture of ethylene ... more Electrochemical studies were performed using Ni electrodes in solutions of a mixture of ethylene glycol or of γ-butyrolactone with 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The aim of the study was to evaluate the use of these systems in electrochemical double-layer capacitor. Cyclic voltammetry experiments showed a potential range at which the Ni electrode behaved as a polarizable electrode. Ni oxidizes at high anodic potentials. Inside the potential range without electrochemical activity, the capacitance and the solution resistance, which were evaluated by impedance electrochemical spectroscopy, were compared for the two solutions tested. Conductivity measurements of the electrolytes with different compositions were also acquired. The results of cyclic voltammetry indicated that the Ni has a wide electrochemical window and low current peak densities of oxidation in the γ-butyrolactone medium than in ethylene glycol medium. The γ-butyrolactone and 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solutions had the highest conductivity values. Decreased 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid content in different solvent mixtures resulted in an increase in the capacitance value at the Ni/electrolyte interface. The highest capacitance values were obtained for Ni in ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate medium.
Journal of Applied Electrochemistry, 2009
This study compares two series of solvents for application in aluminum electrolytic capacitors: e... more This study compares two series of solvents for application in aluminum electrolytic capacitors: ethylene glycol (EG) and water mixtures, and ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate (BMI.BF4) ionic liquid (IL) mixtures. Electrochemical impedance spectroscopy and cyclic voltammetry were carried out with a previously anodized aluminum disk electrode. Comparative measurements of solution resistance, polarization resistance, AC capacitance, and passive current were made. The results show that EG–IL mixtures with low amounts of IL (10% IL–90% EG v/v) have a low solution resistance. Low values of solution resistance, high values of polarization resistance, small passive current, and uniform capacitance of anodized aluminum in EG–IL mixtures are favorable properties of the BMI.BF4 IL for use as an electrolyte in the construction of electrolytic aluminum capacitors.
Corrosion Science, 2011
The stability of electrochemically passivity aluminium has been investigated in mixtures of ethyl... more The stability of electrochemically passivity aluminium has been investigated in mixtures of ethylene glycol, 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid, Na2B4O7.10H2O and NaH2PO4. The effects of (i) borax and sodium dihydrogen phosphate salts presence, (ii) water absorption and (iii) ethylene glycol content are studied by electrochemical impedance spectroscopy (EIS). The results show a decrease in the polarization resistance and an increase in the capacitance associated with the passive oxide dielectric properties with an increase in the water and/or ethylene glycol content in the mixtures. The presence of Na2B4O7.10H2O and NaH2PO4 salts stabilize the oxide layer.► The Al anodic film is stable in BMI.BF4 ionic liquid. ► The solution resistance diminishes when ethylene glycol (EG) is added on BMI.BF4. ► The capacitance of Al anodic film increases in wet BMI.BF4 and EG mixtures. ► The Al anodic film resistance diminishes in wet BMI.BF4 and EG mixtures. ► Borate and phosphate stabilize the Al anodic film in wet electrolyte environment.