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

Effect of Water Content in the Gas Diffusion Layer of H2/O2 PEM Fuel Cell

The heart of a fuel cell is the membrane-electrode assembly consisting of two porous electrodes, where the electrochemical reactions take place, and the ionomer conductive membrane, which allows the proton exchange from the anode to the cathode. The porosity of the electrodes plays an important role in the fuel cell performance. One of the drawbacks presented by the porous electrodes is the accumulation of water in their structure, which implies a hindrance for the reactive gas transport to reach the catalytic reactive sites. In this paper, a mathematical model of a porous electrode, assuming single pores with uniform distribution, is introduced to determine the influence of water accumulation in the electrode on the fuel cell performance under different operating conditions. It is demonstrated that at low current densities, water accumulation has no effect in the fuel cell behavior, whereas at high current densities its performance is severely affected

The influence of carbon monoxide on the voltammetric behaviour of nickel in acid solutions

The voltammetric behaviour of nickel in acid solutions is considerably modified by the presence of CO. As in plain acid the voltammogram also exhibits two main anodic peaks, but in this case, the adsorption of CO on the nickel surface shifts the metal electrodissolution to more positive potentials, and increases the contribution of the second electrooxidation current peak at the expense of the first one. The latter is the main peak in CO-free acids. The presence of CO adsorbates also decreases the charge of the Ni(OH)2/NiOOH redox couple in alkaline solutions. The potential shift of the nickel electrooxidation reaction in acids follows the trend which is expected from the energy difference between CO and H2O adsorption on nickel in the gas phase.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Nanocatalysts for ethanol oxidation: Synthesis and characterisation

Carbon-supported binary PtSn/C and ternary PtSnNi/C catalysts were prepared for the electro-oxidation of ethanol. The carbon-supported nanoparticles were synthesised by employing a modified polyol methodology and characterised in terms of structure, morphology and composition by using XRD, EDX and TEM techniques. Their electrocatalytic behaviour for ethanol oxidation (EO) was investigated by employing a disccomposite electrode covered by a thin layer of catalyst imbedded in a Nafion polymer electrolyte film. An enhancement of the EO through a negative shift of the onset oxidation potential and higher current density at constant potentials were observed on the PtSnNi/C electrodes as compared to those for PtSn/C electrodes. The temperature was changed in the range 40 °C ≤ t ≤ 80 °C, and the variation of the activation energy calculated by linear regression of the Arrhenius plots.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Nanocatalysts for ethanol oxidation: Synthesis and characterisation

Carbon-supported binary PtSn/C and ternary PtSnNi/C catalysts were prepared for the electro-oxidation of ethanol. The carbon-supported nanoparticles were synthesised by employing a modified polyol methodology and characterised in terms of structure, morphology and composition by using XRD, EDX and TEM techniques. Their electrocatalytic behaviour for ethanol oxidation (EO) was investigated by employing a disccomposite electrode covered by a thin layer of catalyst imbedded in a Nafion polymer electrolyte film. An enhancement of the EO through a negative shift of the onset oxidation potential and higher current density at constant potentials were observed on the PtSnNi/C electrodes as compared to those for PtSn/C electrodes. The temperature was changed in the range 40 °C ≤ t ≤ 80 °C, and the variation of the activation energy calculated by linear regression of the Arrhenius plots.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

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

Nanocatalysts for ethanol oxidation: Synthesis and characterisation

Carbon-supported binary PtSn/C and ternary PtSnNi/C catalysts were prepared for the electro-oxidation of ethanol. The carbon-supported nanoparticles were synthesised by employing a modified polyol methodology and characterised in terms of structure, morphology and composition by using XRD, EDX and TEM techniques. Their electrocatalytic behaviour for ethanol oxidation (EO) was investigated by employing a disccomposite electrode covered by a thin layer of catalyst imbedded in a Nafion polymer electrolyte film. An enhancement of the EO through a negative shift of the onset oxidation potential and higher current density at constant potentials were observed on the PtSnNi/C electrodes as compared to those for PtSn/C electrodes. The temperature was changed in the range 40 °C ≤ t ≤ 80 °C, and the variation of the activation energy calculated by linear regression of the Arrhenius plots.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Electrochemical formation and cathodic dissolution of a thin cuprous oxide film on copper in alkaline aqueous solution

The present report refers to the potentiodynamic characteristics of the electrochemical formation and cathodic dissolution of the thin Cu20 film which participates in the electrodissolution of copper in aqueous alkaline solutions at 25 °C.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Characterization of materials for the design and development of collectors and receivers of concentration solar thermal radiation

El trabajo que se presenta muestra el estudio de diferentes materiales a utilizar en el diseño de colectores y receptores para usar en la construcción de prototipos innovadores que usen tecnología basada en el empleo de la Energía Solar Térmica de Concentración (ESTC), para la generación de calor y electricidad. Se estudiaron las propiedades ópticas de los diferentes materiales propuestos, así como su estabilidad térmica y durabilidad ya que con ellos se construirán, específicamente, los componentes de la tecnología de sistema de Colector cilíndrico Parabólico (CCP). Con el propósito de alcanzar mayor eficiencia en el proceso de transformación de energía, se optimizaron, a través del diseño y la simulación, diversas geometrías del dispositivo, que se articularán a los sistemas de seguimiento de la radiación solar en la unidad CCP prototipo, tomando en consideración las regiones geográficas de aplicación.The work presented shows the study of different materials to be used in the design of collectors and receivers to be used in the construction of innovative prototypes that use technology based on the use of Solar Thermal Concentration Energy (ESTC), for the generation of heat and electricity.The optical properties of the different materials proposed were studied, as well as their thermal stability and durability, since with them the components of the Parabolic Cylindrical Collector (CCP) system technology will be specifically built. In order to achieve greater efficiency in the energy transformation process, various geometries of the device were optimized through design and simulation, which will be linked to the solar radiation monitoring systems in the prototype CCP unit, taking into consideration the geographical regions of application.Facultad de Ciencias Astronómicas y Geofísica

A comparative study of electrochemical and optical properties of rhenium deposited on gold and platinum

Rhenium-containing films were grown on gold and platinum after different potentiostatic and potentiodynamic polarizations in the - 0.20 V to 0.70 V range (vs rhe) in aqueous acid perrhenate. Experimental data were obtained using cyclic voltammetry and ellipsometry, from which the thickness and optical indices of the electrodeposited rhenium layer were calculated. Metallic rhenium deposition on gold takes place at potentials within the hydrogen evolution reaction. Rhenium oxide on platinum is formed in the hydrogen adatom potential domain, whereas metallic rhenium is deposited concurrently with the hydrogen adsorption and evolution reactions on the same metal.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada