Kinetics and mechanism of the oxygen evolution reaction at oxide-coated Co-Ni amorphous alloy electrodes

Oxygen evolution reaction (o.e.r.) kinetics in NaOH solutions have been studied on both fresh and oxide covered Co50Ni25Si15B10 amorphous alloy (G-16) electrodes. Steady state polarization curves obtained in different aqueous xM NaOH (0.1 ⩽ x ⩽ 4) in the 30–80°C range fulfill Tafel relationships at low overpotentials; the Tafel slope is close to 2.3(RT/F) V dec−1 for both G-16 and oxide coated G-16 electrodes. At high overpotentials, ohmic relationships with slopes becoming increasingly steep, regardless of the NaOH concentration, are observed. In the Tafel region, the reaction order with respect to OH− is near 2. The apparent current density at constant potential, for oxide coated G-16 electrodes, is greater than that for uncoated G-16. The high catalytic activity of the oxide coated G-16 for the o.e.r. is attributed to its spinel-type structure. The kinetics of the o.e.r. at low overpotentials is explained through a mechanism involving a first electron transfer step followed by a rate-determining chemical step.Facultad de IngenieríaInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Catalytic polyaniline-supported electrodes for application in electrocatalysis

Polyaniline (Pani) films prepared on Au wires were employed as substrates to deposit Pt, Pt-Ru, Pt-Os, Pt-Mo and Pt-Ru-Os or Pt-Ru-Mo by using appropriate working solutions and a potential-programmed perturbation. The atomic percentages of the different metals on Pani were determined by EDAX and their particle size and distribution by SEM. The catalytic activity was tested for adsorbed CO and CH₃OH electrooxidation. Accordingly, the best binary and ternary metal combination resulted in Pt-Ru and Pt-Ru-Os.Facultad de Ciencias ExactasInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

A catalytic platinum–ruthenium–polyaniline electrode for methanol oxidation

Polyaniline films prepared on Au wires were employed as substrates to deposit Pt and/or Ru using a potential-programmed perturbation. Different compositions of Pt and Ru ions in acid electrolyte were employed to decorate the electrodes. The atomic percentages of Pt and Ru on Pani were determined by EDAX and particle size and distribution by SEM. The catalytic activity was tested for adsorbed CO and CH3OH electrooxidation. Nanoparticles of Pt–Ru with different Pt–Ru contents were obtained and characterized for each reaction.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

A study of the optimal conditions for the development of preferred oriented platinum surfaces by means of fast square wave potential perturbations

Changes in the voltammetric response of polycrystalline platinum in the direction expected for preferred oriented surface electrodes are achieved after applying a fast repetitive square wave potential signal covering the potential range of H‐ and O‐electroadsorption/electrodesorption. The influence of the characteristics of the square wave potential signal on the voltammetric response of the modified platinum surfaces is systematically studied to establish the optimal conditions for obtaining surface structures with determined preferred orientations.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta

Aportes de la electroquímica a la arqueología subacuatica

La Electroquímica es una ciencia interdisciplinaria aplicable en múltiples áreas. Básicamente puede decirse que, en relación con la Termodinámica, permite predecir sobre la posibilidad cierta de que ocurra una determinada reacción electroquímica, según el material y el medio, en base al ordenamiento establecido en la Tabla de Potenciales. Por otra parte, a través de estudios cinéticos puede estimarse la durabilidad del material bajo determinadas condiciones. En relación con la arqueología subacuática, se conocen numerosos trabajos relacionados con la protección para la correcta preservación de artefactos metálicos extraídos de naufragios ó sitios arqueológicos sumergidos

Spontaneous Platinum Deposition on Polyaniline Films with Trapped Carbon Nanotubes

A polyaniline film (PANI) with incorporated carbon nanotubes (CNTs) was used as substrate to prepare com-posite platinum electrodes. The polymeric film was grown electrochemically on Nichrome and gold wires from the mo-nomer acid solution with suspended carbon nanotubes. Later, Pt catalytic particles were distributed onto the film by spon-taneous deposition varying the deposition time. The results show that the codeposited CNTs significantly influence notonly the amount but also the dispersion of the Pt particles. Methanol oxidation was chosen as model reaction to test thecatalytic properties of the Pt composites. It was found that those with carbon nanotubes show better catalytic performance.Fil: Bavio, Marcela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; ArgentinaFil: Kessler, Teresita. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ingeniería Olavarría; ArgentinaFil: Castro Luna Berenguer, Ana Maria del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentin

Methanol Electrooxidation on Pt-Ru Catalysts Dispersed in Conducting Polyaniline Films

Methanol electrooxidation was investigated on tailored Pt-Ru-polyaniline catalysts prepared applying dynamic potential routines. The electrodes characterized by SEM, EDX and TEM present a uniform distribution of metal particles about 100 nm in size, composed of Ru and Pt on the fibrous polymer matrix. The effect of concentration in the range 0.05-1 M and temperature in the range 20 to 60 °C on the methanol electrooxidation rate was determined. The apparent activation energy depends on the catalyst Ru content.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Electroless amorphous alloy electrodes : The formation and properties of hydrous oxide coatings in alkaline solution

Amorphous alloys (Co94.6P5.4 and Co71.6Ni Is18.3aP10.1) were prepared by the eleetroless teehnique. Oxide coated amorphous alloys were produced by applying a cyclic potential routine to the amorphous alloys immersed in alkaline solution at 30°C. Oxide coatings were character&d by electrochemical techniques and ir spectroscopy. The electrocatalytic activity of oxide coated amorphous alloy electrodes was tested for the oxygen evolution reaction in alkaline solution at 30°C. The high electrocatalytic activity of these electrodes is explained through the development of a porous hydrous oxide film with a spinel-type structure.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Kinetics and mechanism of the oxygen evolution reaction at oxide-coated Co-Ni amorphous alloy electrodes

Oxygen evolution reaction (o.e.r.) kinetics in NaOH solutions have been studied on both fresh and oxide covered Co50Ni25Si15B10 amorphous alloy (G-16) electrodes. Steady state polarization curves obtained in different aqueous xM NaOH (0.1 ⩽ x ⩽ 4) in the 30–80°C range fulfill Tafel relationships at low overpotentials; the Tafel slope is close to 2.3(RT/F) V dec−1 for both G-16 and oxide coated G-16 electrodes. At high overpotentials, ohmic relationships with slopes becoming increasingly steep, regardless of the NaOH concentration, are observed. In the Tafel region, the reaction order with respect to OH− is near 2. The apparent current density at constant potential, for oxide coated G-16 electrodes, is greater than that for uncoated G-16. The high catalytic activity of the oxide coated G-16 for the o.e.r. is attributed to its spinel-type structure. The kinetics of the o.e.r. at low overpotentials is explained through a mechanism involving a first electron transfer step followed by a rate-determining chemical step.Facultad de IngenieríaInstituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Preparation and modification of hydrous thick cobalt oxide layers : Voltammetric characteristics of rough Co₃O₄-spinel-type electrodes

The application of a periodic perturbing potential to a cobalt electrode immersed in alkaline solutions at room temperature allows accumulation of a hydrous cobalt hydroxide overlayer which becomes a precursor to the production of a rough Co3O4 spinel film through subsequent thermal treatment at 480°C. The optimal working conditions for the application of this procedure are discussed. The properties of the resulting overlayers were determined through voltammetry, X-ray analysis, infrared spectroscopy, thermal gravimetric and differential thermal analysis, and SEM micrography. The explanation of the entire process is given in terms of sequential electrochemical oxidation and reduction reactions involving different Co-containing species. The electroreduction reactions including the HER, play an important role in determining the characteristics of the resulting Co3O4 overlayer.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada