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Bimetallic oxides have significant attraction as supercapacitor electrode materials due to their highly reversible redox processes, which are commonly associated with their surface chemistry and morphological features. Here, we report the synthesis, characterization, and electrochemical evaluation of bimetallic oxides with different molar compositions of Co and V (Co

PtPd bimetallic catalysts supported on hierarchical porous carbon (HPC) with different porous sizes were developed for the oxygen reduction reaction (ORR) toward fuel cell applications. The HPC pore size was controlled by using SiO

A new family of PtFe catalysts supported on hierarchical porous carbon (HPC), with different porous sizes, was developed and tested as cathodes in oxygen reduction reaction in acetate-fed microbial fuel cells. The results obtained were compared with carbon black (CB), CB-PtFe supported catalysts. HPC400 was characterized by cyclic voltammetry, showing a good electrolyte accessibility in contrast to CB. The XPS analysis of HPC supports show a low content of oxygenated species on carbon surfaces. The morphological and structural properties of catalysts were characterized by SEM-EDX and XRD. The electrochemical performance was examined by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The CO stripping voltammetry was applied for the determination of the surface area of PtFe catalysts; these experiments were carried out in a three-electrode system. In oxygen reduction experiments by LSV, HPC400-PtFe and CB-PtFe show good current densities of − 10.3 mA cm−2 and − 9.09 mA cm−2, respectively. HPC300-PtFe presents the poorest performance (− 2.3 mA cm−2). The HPC500-PtFe is the catalyst with the major current density (− 26.19 mA cm−2). A similar behavior is obtained in microbial fuel cell (MFC) catalyst performances; the MFCs were evaluated during 16 days until biofilm formation and stabilization. An increment of the power density was observed with the number of days. The power density obtained for HPC500-PtFe was 3218.89 mW m−2, showing better performances compared with CB-PtFe (743.18 mW m−2), HPC400-PtFe (578.82 mW m−2), and HPC300-PtFe (266.82 mW m−2). Hierarchical porous structure in combination with large-sized macropores enhanced the catalytic activity of PtFe toward oxygen reduction reaction in microbial fuel cells.

The generation of filaments constituted by nanocomposites allows printing pieces with functional properties. A method is proposed for incorporating nanoparticles in plastic filaments (thermoplastic polyurethane, PU) by diffusion in the swollen material. The nanoparticles must be dispersed in solvents (or solvent mixtures) in which the polymer swells but does not dissolve. Nanoparticles are incorporated mainly at the surface as revealed by SEM/EDS mapping. The thermal properties (studied by DSC and TGA) of the PU are only slightly affected by the presence of NPs. Test pieces successfully are printed using the modified filaments. Incorporation of solid lubricant (MoS2) nanoparticles decreases the coefficient of friction of the printed test samples.

In this work, we studied in detail one of the possible limiting-steps during CO oxidation at Pt and Pt/Au electrodes, namely CO adsorption and diffusion at the electrode's surface. With this aim, we used an electroless method for Pt surface modification, which entails the spontaneous deposition of gold at Pt electrodes. We also use a home-made fast-response (four electrodes) flow cell that allows an accurate control of the electrode exposition time to CO (tad) and of the time interval (tw) before stripping of the adsorbed CO (COad). Thus two key experimental parameters of the electro-oxidation process can be independently modified and the results evaluated. Our results are consistent with a mechanism in which CO is initially adsorbed onto active sites and then moves away by surface diffusion. As a result, the subsequent oxidative stripping elimination of CO starts with COad far away from the most active sites. The experiments carried out for Pt/Au electrodes with different fraction of electrode area covered by CO (θCO) demonstrate that Au acts as a barrier, hindering the surface diffusion of CO from/to the active sites, giving raise to the multiple pecks observed when tw is low. Fil: del Giudice, Gabriela Andrea. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina. Universidad Nacional de Río Cuarto; Argentina Fil: Tesio, Alvaro Yamil. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Cappellari, Paula Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina. Universidad Nacional de Río Cuarto; Argentina Fil: Palacios, Rodrigo Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto; Argentina. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Planes, Gabriel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Río Cuarto; Argentina. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina

In this study, a new electrochemical sensor for determination of cyanide is proposed. The sensor is formed by a carbon paste electrode modified with hierarchical porous carbon and silver sulfide nanoparticles. The morphology characterization was performed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), while the chemical and electrochemistry characterization were performed by energy dispersive X-ray spectroscopy and cyclic voltammetry, respectively. Under the optimized conditions, the Ag2SNPs-HPC300 sensor presented a large concentration linear range of 5.9 × 10−7 to 1.1 × 10-3 mol L-1, and limit of detection of 7.0 × 10-8 mol L-1 using square-wave adsorptive anodic stripping voltammetry (SWAdASV) technique. The analytical response of the Ag2SNPs-HPC300 sensor was evaluated in presence of different compounds, and the results showed a RSD of 4.3% in triplicate experiments. The applicability of the Ag2SNPs-HPC300 sensor in river water samples contaminated with cyanine showed recoveries values near 100%. The developed method exhibited high sensitivity and selectivity, good reproducibility, repeatability and low-cost, demonstrating to be a very promising analytical alternative for determination of cyanide in this matrix. Fil: Cárdenas Riojas, Andy A.. Universidad Nacional de Ingenieria; Perú Fil: Wong, Ademar. National Institute For Alternative Technologies Of Detection; Brasil Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Sotomayor, Maria D. P. T.. Universidade de Sao Paulo; Brasil Fil: La Rosa-Toro, Adolfo. Universidad Nacional de Ingenieria; Perú Fil: Baena Moncada, Angélica María. Universidad Nacional de Ingenieria; Perú

In the current work the concept of the active site is analyzed. With this end, Pt was deposited on Au(111) electrode assisted by water in oil microemulsion, in which the micelles confine the formation of small Pt clusters. The presence of highly and lowly coordinated Pt atoms was finely tuned by controlling the annealing processes and confirmed by CO stripping voltammetry in conjunction with scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). This procedure allowed for the individuation of the effects of materials free and rich of catalytic defect sites on the CO electrochemical oxidation profile. Thus, a clear correlation between low-coordinated Pt atoms and the appearance of CO oxidation peaks at more negative potentials (peaks at 0.26 and 0.59 V vs. RHE) compared to high-coordinated Pt atoms (ca. 1.1 V vs. RHE) was identified.

The electrochemical behavior and mass spectrometric features for ethanol reactions on nanostructured mesoporous platinum catalysts (MPPt) in 0.5 M H2SO4 were studied for the first time as function of the alcohol concentration. With this purpose, cyclic voltammetry and chronoamperometry techniques were combined with a new configuration of an electrochemical mass spectrometry (EC-MS), which allows high detection sensitivity with low amount of catalysts. Accordingly, a comprehensive study of the reaction mechanism and kinetics of the ethanol oxidation on MPPt in acidic medium was carried out. The water dissociation reaction and the first ethanol dehydrogenation step are proposed to be the rate-determining step (rds) for the complete ethanol oxidation reaction and the acetaldehyde production, respectively. Furthermore, acetaldehyde, acetic acid and CO2 formation were monitored during the ethanol electrooxidation reaction and the energy conversion efficiency from ethanol to CO2 was calculated. Results indicate an increment of by-side products (acetaldehyde and acetic acid) maintaining equal CO2 formation with the rise of the alcohol concentration. Consequently, the highest energy conversion efficiency to CO2 (∼11%) was achieved at 0.6 V with the lowest alcohol concentration employed (0.01 M). Results were analyzed in terms of density and type of active surface sites, applied potential and alcohol concentration.

A comparative study of the Pt and Pt/Au surface towards CO and formic acid oxidation was performed by conventional electrochemical techniques used in combination with an electrochemical flow cell (four-electrode configuration) and in-situ Fourier Transform Infrared Spectroscopy. With this purpose, a polycrystalline Pt electrode was modified by spontaneous deposition of gold atoms, achieving a gold surface coverage (θ) in the range of 0 ≤ θ ≤ 0.47. Formic acid and carbon monoxide electrooxidation on polycrystalline Pt and Au-modified Pt surfaces were studied by cyclic voltammetry, linear sweep voltammetry, chronoamperometry and in-situ FTIR techniques. The electrochemical and in-situ FTIR evidence collected for CO and FA oxidation on Pt/Au support the idea of a strongly modified Pt surface. At the Pt/Au electrode, Au operates as a barrier between surface domains, and the main observable result is the uncoupling of the catalytic activity. The free (fast) surface diffusion of reactants at a low potential, which leads to characterize Ptpc as a “homogeneous surface” towards CO and FA oxidation, is not possible when Au is present.

Fil: Arias, Analia Natali. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy. - Universidad Nacional de Jujuy. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy. - Gobierno de la Provincia de Jujuy. Centro de Investigacion y Desarrollo En Materiales Avanzados y Almacenamiento de Energia de Jujuy; Argentina

The Formic Acid Electro-oxidation (FAEO) on Pt/Au Nanoparticles (PtAu NP) supported on Hierarchical Porous Carbon (HPC), was studied by cyclic voltammetry and chronoamperometry. The supported HPC-Pt nanoparticles were surface modified by Au spontaneous deposits. The morphological and compositional characterization was performed by Scanning Electron Microscopy (SEM) coupled with Electron Dispersive Spectroscopy (EDS). A significant increase of the current densities for FAEO in the potential region 0.1?0.75 V RHE was observed on HPC-PtAu catalysts. The comparison with HPC-Pt electrodes results show that Au atoms presence on Pt nanoparticles is a key factor to improve the catalysts performance. Based on our results, a clear change in FAEO mechanism on HPC-PtAu catalysts with respect to HPC-Pt was evidenced. Fil: Cappellari, Paula Sofía. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Baena Moncada, Angélica María. Universidad Nacional de Ingenieria; Perú Fil: Coneo Rodríguez, Rusbel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Moreno, Mario Sergio Jesus. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina Fil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Tecnologías Energéticas y Materiales Avanzados; Argentina

N-containing monolithic porous carbon material with dual micro and mesoporous structures was synthesized using an innovative, cheap and easy synthesis route based on the classical resorcinol-formaldehyde synthesis. A completely chemical, structural and morphological characterization was carried out. The N content in the carbonaceous material was 7.3% and XPS data showed that is present in two different surrounds, as N-pyrrolic and N-pyridinic atoms. Is known that, the last one, can acts as a catalyst at surface level in heterogeneous reactions. In addition, using this material, we were able to fabricate lithium-ion and lithium-sulfur batteries obtaining high values of discharge capacity and cycle stability and demonstrating the multifunctional character of this carbon in energy storage devices. Fil: Tesio, Alvaro Yamil. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Arias, Analía Natalí. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Jujuy; Argentina. Centro de Investigación y Desarrollo en Materiales Avanzados y Almacenamiento de Energía de Jujuy; Argentina Fil: Morales, Julián. Universidad de Córdoba; España Fil: Planes, Gabriel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Caballero, Alvaro. Universidad de Córdoba; España

The performance of electrodes modified with electrochemically generated cobalt oxide nanoparticles for the oxidation of As(III) species was investigated by cyclic voltammetry (CV) and rotating disk voltammetry (RDV). The oxide nanoparticles were made by electrodeposition from cobalt oxides using CV without the reduction of water or anions. Controlling deposition parameters, different values of surface concentration (Γ) can be obtained. Electrochemical experiments (CV and RDV at different rotation rate) showed a shift in the As(III) oxidation potentials to lower values; when the coverage surface increased, these differences in the surface concentration produced a potential shift of up to 150 mV. This phenomenon depends on the ratio of the electrode active area to the geometric area (Ψ). The Levich and Koutecký-Levich analysis of RDV voltammetric data confirmed that the oxidation of As(III) on modified electrodes is controlled by mass transport. It was also demonstrated that different values of surface concentration produces different kinetic current values. Fil: Coneo Rodriguez, Rusbel. Comisión Nacional de Energia Atomica. Gerencia D/area de Seguridad Nuclear y Ambiente; Argentina Fil: Baena Moncada, Angélica María. Universidad Nacional de Ingeniería. Facultad de Ciencias; Perú Fil: Acevedo, Diego Fernando. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química y Física; Argentina Fil: Morales, Gustavo Marcelo. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química y Física; Argentina Fil: Planes, Gabriel Angel. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química y Física; Argentina Fil: Barbero, César Alfredo. Universidad Nacional de Rio Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química y Física; Argentina

A high surface macroporous porous carbon (MPC) has been obtained by SiO2 nanoparticles template and further used as support for PtRu catalysts. MPC supported PtRu materials show an enhanced activity for methanol electrooxidation when compared with commercial catalysts. This observation is discussed in terms of reactant accessibility to active sites. The improved diffusion through the porous matrix influences not only methanol feeding, but also removal of reaction subproducts, as clearly shown by differential electrochemical mass spectrometry (DEMS). Fil: Baena Moncada, Angélica María. Universidad Nacional de Río Cuarto; Argentina Fil: Coneo Rodriguez, Rusbel. Universidad Nacional de Río Cuarto; Argentina Fil: Calderon, Juan Carlos. Universidad de la Laguna; España Fil: Florez Montaño, Jonathan. Universidad de la Laguna; España Fil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto; Argentina Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto; Argentina Fil: Rodriguez, Jose Luis. Universidad de la Laguna; España Fil: Pastor, Elena. Universidad de la Laguna; España

The effects of catalyst matrix porosity composition on the catalytic performance have been studied using sulfonated mesoporous SBA-15 silica. The matrix was sulfonated with three different methods grafting, in situ oxidation, and carbon infiltration. Additionally, unordered sulfonated mesoporous carbon, and the commercial catalysts Amberlite IR-120 and Nafion 117 were tested. The catalytic performance was evaluated in a Fischer esterification using acetic acid and ethanol, as well as in a transesterification of triglycerides (sunflower oil) and ethanol to produce biodiesel. The study shows that for long carbon chains, the effective wetting of the porous catalyst matrix by the reactants is most important for the catalytic efficiency, while for shorter carbon chain, the mass transport of the reagents trough the porous structure is more important. The catalysts were analysed using electron microscopy and physisorption. The study shows that the reactions are faster with carbon infiltrated materials than the silica materials due to a higher concentration of sulfonic groups linked to the carbon. The in situ functionalized SBA-15 is a more efficient catalyst compared to the post grafted one. All the synthesized catalysts outperform the commercial ones in both reactions in terms of conversion. (C) 2017 Elsevier B.V. All rights reserved. Funding Agencies|SUMA2 Network Project, 7th Framework Program of the European Commission (IRSES) [318903]; Knut and Alice Wallenberg Foundation [KAW 2012.0083]; CONICET; FONCYT; MinCyT-Cordoba; SECYT-UNRC

The fabrication and catalytic properties of hierarchical porous carbon loaded with PtRu particles was studied. A silica nanoparticles opal is filled with resorcinol/formaldehyde resin, which is then pyrolized to form a macroporous carbon. Depending on synthesis conditions the volume contraction induces mesopore formation in the macroporous carbon, creating a hierarchical porous carbon (HPC). The material consists of a thick, highly porous electrocatalytic film. PtRu nanoparticles were loaded inside the HPC by reduction of metallic ions with formic acid. The electrocatalytic activity toward CO and methanol oxidation was evaluated. The current densities for methanol electrooxidation at 60 °C (220 μA cm −2 and 120 Ag −1 at 0.55 V RHE ) reveals high activity, suggesting that the catalysts consist of well disperse, small PtRu nanoparticles, with a low degree of agglomeration and good accessibility for reactants.

The electrochemical behaviour of fuel cell catalysts (mesoporous Pt (MPPt), MPPtRu, MPPt modified by adsorbed Ru (MPPt/Ru) and carbon supported PtRu alloy) was studied using the thin layer flow cell differential electrochemical mass spectrometry (TLFC-DEMS) technique. The catalysts present high catalytic activity towards the methanol oxidation reaction (MOR), being the PtRu/C electrode the least active for MOR, while MPPt/Ru presents higher current densities for this reaction than MPPtRu. The results suggest that the diffusion properties obtained in the porous structure of the MP electrodes and the surface atomic arrangement in the electrode are the main reasons for the higher catalytic activity achieved. Finally, TLFC-DEMS was proved to be a powerful technique which evaluates and correlates the CO 2 efficiency with the catalytic activity and the porous structure of the catalysts.

Mesoporous Pt and Pt/Ru catalysts with 2D-hexagonal mesostructure were synthesized using a triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymer (Pluronic F127 ® ) template, on a gold support. Large electrochemical surface areas were observed for the catalysts prepared at high overpotentials. Compared to the Pt catalyst, the Pt/Ru alloy containing 3 at% of Ru exhibited lower onset potential and more than three times the limit mass activity for methanol oxidation. This behavior is assigned to the larger pore size of the mesoporous Pt and Pt/Ru catalysts obtained with this template that seems to improve the methanol accessibility to the active sites compared to those obtained using lyotropic liquid crystals.

Sequential electropolymerization of aniline followed by an aniline derivative bearing an ion moiety is presented. The studied derivatives contain sulfonic, carboxylate or amino groups. Its electrochemical behavior at acid and neutral pH is studied by cyclic voltammetry combined with quartz crystal microbalance or probe beam deflection in order to assess the mass transfer process involved in these new modified electrodes. All of them show a stable and quasi-reversible electrochemical behavior at neutral pH that can be attributed to a self-doping process. These new modified electrodes can be further modified due to the presence of functional groups.

Porous vitreous carbon can be produced by pyrolysis of resorcinol-formaldehyde porous resin. Using surfactants as stabilizers, it is possible to dry the porous resin in air without pore collapse. Having a large surface area (>500 m2/g) and high electronic conductivity makes the materials suitable as support of electrocatalyst nanoparticles. Pt nanoparticles were prepared by a microemulsion method and impregnated into the carbon pores by adsorption from its suspension. The presence of the Pt nanoparticles is easily detected by the electrochemical reduction of proton and the evolution of H2, detected by DEMS. The cyclic voltammogram of the modified electrode in presence of CO does not show current due to CO oxidation to CO2. On the other hand, the differential electrochemical mass spectroscopy (DEMS) signal clearly shows CO2 production. Methanol can be electroxidized on the electrode containing Pt nanoparticles supported on porous carbon.

Polymer electrolyte fuel cells constitute one of the most important efficiency energy converters for non-centralised uses. However, the use of fuels arising from reformate processes significantly lowers the current efficiency because of anodic catalytic poison coming from adsorbed carbon monoxide (COad). In this work, the influence of the addition of hydrogen peroxide in the flow current is studied, considering the adsorption and electrochemical oxidation of carbon monoxide on carbon-supported Pt (20% Pt/Vulcan) and Pt:Ru (1:1, 20% Pt:Ru/Vulcan) catalysts in 2 M sulphuric acid. The investigation was conducted applying cyclic voltammetry and on-line differential electrochemical mass spectrometry. A series of experiments has been performed to investigate the influence of the temperature as well as the time of contact and the concentration of hydrogen peroxide. Oxidation of COad to carbon dioxide occurs at lower potentials in the presence of hydrogen peroxide. Moreover, it is possible to remove ca. 70% of COad on Pt/C electrodes. On the other hand, for PtRu/C electrodes, similar charge values to those of Pt/C electrodes were obtained for the CO stripping, but the process occurs at more negative potentials. In this case, the effect of partial desorption for COad by interaction with hydrogen peroxide is added to the bifunctional mechanism usually considered for this alloy.

Electrodeposited mesoporous (MP) Pt electrodes were evaluated as catalysts for CO and methanol electrooxidation. Electrochemical analysis reveals a mass activity of 41 Ag−1 at 0.55 V in 1 M CH3OH, similar to carbon supported catalysts. However, the high current densities are related to low CO2 conversion efficiencies, as was established by using differential electrochemical mass spectrometry in a thin layer flow cell configuration (TLFC-DEMS). These results can be understood taking into account the especially accessible porous structure of the MP Pt, where the possibility of readsorption of partially oxidized products is low. Keywords: DEMS, Micro fuel cells, Methanol electrooxidation, Mesoporous metal, Liquid crystal

Formic acid and adsorbed carbon monoxide electrooxidation on polycrystalline Pt and Au-modified Pt surfaces were studied by cyclic voltammetry, lineal sweep voltammetry and in-situ Fourier transform infrared spectroscopy techniques. With this purpose, a polycrystalline Pt electrode was modified by spontaneous deposition of gold atoms, achieving a gold surface coverage (θ) in the range of 0 ≤ θ ≤ 0.47. Results indicate the existence of two main pathways during the formic acid oxidation reaction, i.e. dehydration and dehydrogenation routes. At higher potentials than 0.5 V the dehydrogenation pathway appears to be the operative at both Pt and Au electrodes. Meanwhile, the dehydration reaction is the main pathway for Pt at lower potentials than 0.5 V. It was found that reaction routes are easily tuned by Au deposition on the Pt sites responsible for the formic acid dehydration reaction, and hence for the catalytic formation of adsorbed carbon monoxide. Gold deposition on these Pt open sites produces an enhanced activity toward the HCOOH oxidation reaction. In general terms, the surface inhibition of the reaction by adsorbed intermediates (indirect pathway) is almost absent at gold-modified Pt electrodes, and therefore the direct pathway appears as the main route during the formic acid electrooxidation reaction. Fil: Cappellari, Paula Sofía. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: García, Gonzalo. Universidad de la Laguna; España Fil: Florez Montaño, Jonathan. Universidad de la Laguna; España Fil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Pastor, Elena. Universidad de la Laguna; España Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Metallic mesoporous (MP) catalysts with large surface area can be obtained in-situ, in a single step, by electrochemical reduction. In this work, the electrochemical behavior of MPPt and Sn modified mesoporous Pt (MPPt/Sn) was studied and compared with commercial carbon supported PtSn alloy (3:1). The electrochemical activity toward carbon monoxide and methanol oxidation reactions were evaluated by cyclic voltammetry and chronoamperometry, whereas X-ray photoelectron spectroscopy was used to determine the surface composition and oxidation state of the atoms in the top layers of the catalysts. The analysis of methanol conversion to CO2 was performed with aid of differential electrochemical mass spectrometry (DEMS). Results reveal a better performance of the MPPt/Sn, which shows higher current density and energy conversion efficiency of fuel to CO2 than conventional carbon supported PtSn alloy (3:1). Fil: Flórez Montaño, Jonathan. Universidad de La Laguna; España Fil: García, Gonzalo. Universidad de La Laguna; España Fil: Rodríguez, José L.. Universidad de La Laguna; España Fil: Pastor Cavada, Elena. Universidad de La Laguna; España Fil: Cappellari, Paula Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Planes, Gabriel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina

We report a synthetic approach for the production of ultra-small (0.6 nm) gold nanoparticles soluble in water with a precise control of the nanoparticle size. Our synthetic approach utilizes a pH-depending Au/cysteine polymer as a quencher for the AuNPs grown. The method extends the synthetic capabilities of nanoparticles with sizes down to 1 nm. In addition to the strict pH control, the existence of free -SH groups present in the mixture of reaction has been observed as a key requirement for the synthesis of small nanoparticles in mild conditions. UV-Vis, SAXS, XANES, EXAFS and HR-TEM, has been used to determinate the particle size, characterization of the gold precursor and gold-cysteine interaction. Fil: Cappellari, Paula Sofía. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Buceta, David. Universidad de Santiago de Compostela; España Fil: Morales, Gustavo Marcelo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Moreno, Mario Sergio Jesus. Comision Nacional de Energia Atomica. Centro Atomico Bariloche; Argentina Fil: Giovanetti, Lisandro Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Ramallo Lopez, Jose Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Requejo, Felix Gregorio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; Argentina. Universidad Nacional de La Plata; Argentina Fil: Craievich, Aldo F.. Universidade de Sao Paulo. Instituto de Física; Brasil Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina

(Figure Presented) Good organizational skills: Evidence for the formation of Pt clusters during classical microemulsion synthesis was obtained by scanning tunneling microscopy. The Pt clusters were spontaneously assembled on an Au(111) surface to form high-aspect-ratio objects. 2D nanoislands form and subsequently self-assemble in parallel rows of several hundreds of nanometers in length. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA.

Recent results, part of an ongoing research programme aimed to develop synthetic methods which could be used to functionalise conducting polymers, are described. Among those methods are the copolymerization of aniline with substituted anilines and post-modification reactions of polyaniline, such as: electrophilic substitution, nucleophilic addition and coupling with diazonium salts. Some of those methods could be chemically or electrochemically controlled allowing a quantitative tailoring of the modification. The effect of the added functionalities on the electrochemical properties of the polymers is investigated using spectroscopic and electrochemical techniques. The extension of the synthetic methods to combinatorial modification of conductive polymers is also discussed.

The reactions of benzaldehyde at platinum in 0.1 M HClO4 were studied by means of differential electrochemical mass spectrometry (DEMS) and in situ Fourier transform infrared (FTIR) spectroscopy co...

Differential electrochemical mass spectrometry (DEMS) and Fourier transform infrared spectroscopy (FTIRS) are used to provide evidence of the existence of a free metal surface under electrodeposited polyaniline (PANI) films. With this purpose, both methanol oxidation and CO adsorption are studied on Pt electrodes modified by electrodeposited polyaniline films (PANI/Pt). Using the DEMS signal for CO2 (m/z = 44) to follow the oxidation of adsorbed CO to CO2, the exposed Pt surface area under the film is evaluated to reach ∼30% of the clean Pt electrode. CO adsorption on a PANI/Pt electrode is clearly detected by FTIRS through the bands at 2080 and 1820 cm-1 for linear and bridge bonded CO, respectively. The free area seems to behave differently than clean Pt toward methanol oxidation. The in-situ FTIR spectra present only a band at 2343 cm-1 due to CO2 formation, but not those due to CO adsorption, suggesting a change in the oxidation mechanism.

Poly(N-methylaniline) thin films show different cyclic voltammetric behaviour when cycled in HClO4, HBF4, HCl or HNO3. While in the first two acids the film shows profiles peak potentials similar to those of polyaniline, profiles in HCl and HNO3 show higher peak potentials for oxidation and a different shape. The free energy for the process, calculated from the oxidation peak potential, shows a linear correlation with the free energy of hydration of the anions present in the test solution. An energy cycle for the oxidation process is proposed to explain the results. The reaction mechanism assumes that anions have to lose their hydration shell to form the polymer salt during electrochemical oxidation of the films. Electropolymerization also depends on the anion present in the solution. While this is possible with low hydration energy anions (ClO4−, BF4−), it is difficult or impossible when the electrolyte solution contains other anions (Cl−, NO3−) where a higher oxidation potential of the preformed polymer is observed. © 2002 Society of Chemical Industry

Spectroelectrochemical methods, in-situ Fourier Transform Infrared (FTIR) and Differential Electrochemical Mass Spectroscopy (DEMS), are used to study the formation of poly(N-methylaniline) (PNMANI) by anodic oxidation of N-methylaniline (NMANI). The methods are used to elucidate the structural changes during redox switching of PNMANI and the nature of the degradation products of PNMANI produced during electrochemical oxidation. The results are discussed in comparison with those previously reported for aniline. The early stages of NMANI oxidation leads to the formation of dimers by head-to-tail coupling (product = N,N’-dimethyl-4-aminodiphenylamine, DMADA) and tail-to-tail coupling (product = N,Ń-dimethylbenzidine, DMBz). It seems that, when N-methylaniline is oxidized, it is formed more tail-to-tail dimer than in the case of aniline, due to steric and electronic effects of the N-substituent methyl groups. The head-to-tail dimer (DAMADA) is irreversibly adsorbed on the electrode surface. The elucidation of the reaction mechanism is aided by electrochemical and in-situ spectroelectrochemical studies of N,Ń-dimethylaniline which can only give the tail-to-tail dimer (N,N,Ń,Ń-tetramethylbenzidine, TMB). The in-situ FTIR study of redox behaviour of poly(N-methylaniline) shows that quinonimine units are produced during oxidation. The intensity of the band at 1196 cm−1, assigned to C-N+ stretching in the -C-N+-CH3 moiety, increases due to an increased substituted imine content in the oxidized film. An increase of the anion (perchlorate) concentration inside the film, due to compensation of the positive charges formed during oxidation, is also detected by FTIR. CO2 formation is observed by FTIR during NMANI oxidation and in electrochemically induced polymer degradation. The formation of CO2 is confirmed by DEMS. Additionally, during degradation, indophenol like molecules together with quinone, are produced as the final organic degradation product Fil: Planes, Gabriel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Rodriguez, Jose Luis. Universidad de la Laguna. Tenerife; España Fil: Miras, Maria Cristina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Tejera, Elena Pastor. Universidad de la Laguna. Tenerife; España Fil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina

Ion exchange coupled to oxidation–reduction cycling of electrochromic cobalt oxide films was studied using Probe Beam Deflection (PBD) techniques. The films were deposited by potentiodynamic cycling of glassy carbon electrodes in aqueous Co+2 solution. The cyclic voltammograms of cobalt oxide films present three peaks in basic (pH=13) solution. The PBD signal is positive during oxidation indicating insertion of hydroxide ions. The results are confirmed by monitoring the PBD signal during pulse potential experiments at varying distances of the beam from the electrode. Using the theory of PBD behaviour for discontinuous reactions, a diffusion coefficient for the mobile ion of 1.68×10−5 cm2/s was measured, which agreed with that observed for NaOH diffusion in similar systems. The results are explained on the basis of a scheme of solid state oxidations from CoII to CoIV in three redox steps, coupled to hydroxide ion insertion. Keywords: Cobalt oxide, Probe beam deflection, Electrochromic, Ion exchange, Diffussion coefficient

A modified polyaniline was obtained by coupling of the 4-sulfobenzenediazonium ion with poly ( N -methylaniline) (PNMANI) at temperatures below 5°C and in basic or neutral pH conditions. The FT-IR spectra of the product show all bands due to the poly( N -methylaniline). Additional bands at 1007, 1003 and 623 cm −1 are assigned to the vibrations of the sulfonate group, incorporated in the polymer matrix. A new band at 1485 cm −1 is also present, assigned to the stretching of the azo bond. The polymer is soluble in aqueous base. The results suggest the formation of an azo-substituted poly ( N -methylaniline): poly(4-sulfobenzenazo-( N -methylaniline)) (p(4SBA-NMANI)). The solution spectra show absorption bands at 242, 310 and 595 nm. Thin films deposited on glassy carbon show clear electroactivity. The method could be used to produce electroactive films with bonded functionalities.

The use of high surface monolithic carbon as support for catalysts offers important advantage, such as elimination of the ohmic drop originated in the interparticle contact and improved mass transport by ad-hoc pore design. Moreover, the approach discussed here has the advantage that it allows the synthesis of materials having a multimodal porous size distribution, with each pore size contributing to the desired properties. On the other hand, the monolithic nature of the porous support also imposes new challenges for metal loading. In this work, the use of Hierarchical Porous Carbon (HPC) as support for PtPd nanoparticles was explored. Three hierarchical porous carbon samples (denoted as HPC-300, HPC-400 and HPC-500) with main pore size around 300, 400 and 500 nm respectively, are used as porous support. PtPd nanoparticles were loaded by impregnation and subsequent chemical reduction with NaBH4. The resulting material was characterized by EDX, XRD and conventional electrochemical techniques. The catalytic activity toward formic acid and methanol electrooxidation was evaluated by electrochemical methods, and the results compared with commercial carbon supported PtPd. The Hierarchical Porous Carbon support discussed here seems to be promising for use in DFAFC anodes. Fil: Baena Moncada, Angélica María. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Morales, Gustavo Marcelo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Florez Montano, Jonathan. Universidad de la Laguna; España Fil: Pastor, Elena. Universidad de la Laguna; España

The role of the electrode nanoporosity in electroanalytical processes is discussed and specific phenomena (slow double layer charging, local pH effects) which can be present in porous electrode are described. Hierarchical porous carbon (HPC) materials are synthesized using a hard template method. The three dimensional carbon porosity is examined using scanning electron microscopy on flat surfaces cut using a focused ion beam (FIB-SEM). The electrochemical properties of the HPC are measured using cyclic voltammetry, AC impedance, chronoamperometry and Probe Beam Deflection (PBD) techniques. Chronoamperometry measurements of HPC seems to fit a transmission line model. PBD data show evidence of local pH changes inside the pores, during double layer charging. The HPC are modified by in situ (chemical or electrochemical) formation of metal (Pt/Ru) or metal oxide (CoOx, Fe3O4) nanoparticles. Additionally, HPC loaded with Pt decorated magnetite (Fe3O4) nanoparticles is produced by galvanic displacement. The modified HPC materials are used for the electroanalysis of different substances (CO, O2, AsO3 3). The role of the nanoporous carbon substrate in the electroanalytical data is evaluated. Fil: Coneo Rodriguez, Rusbel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Baena Moncada, Angélica María. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Acevedo, Diego Fernando. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Miras, Maria Cristina. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Barbero, César Alfredo. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Mesoporous deposits of platinum catalysts were electrodeposited over monolith carbon with hierarchical porous structure. The liquid crystal used as a template allowed the electrodeposition of the catalyst on the outer region of the carbon with low penetration in the porous structure. The platinum hexagonal mesostructured deposits exhibits an excellent stability enhanced by the roughness of the carbon support. The mass activity for the electrooxidation of methanol of the mesoporous Pt catalyst supported on the hierarchical carbon is similar to that observed on gold and to that reported for commercial Pt nanoparticulated catalysts, even when this catalyst has a smaller Pt load than the commercial one. Also, the poisoning rate of the mesoporous catalyst is lower than that observed for the commercial catalyst. The integrated system of structured materials could be suitable for the fabrication of modified electrodes in small scale applications. © 2009 Springer Science+Business Media B.V. Fil: Bruno, Mariano Martín. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina Fil: Franceschini, Esteban Andrés. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina Fil: Planes, Gabriel Angel. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Departamento de Química; Argentina Fil: Corti, Horacio Roberto. Comisión Nacional de Energía Atómica. Gerencia del Área de Investigaciones y Aplicaciones no Nucleares. Gerencia de Física (Centro Atómico Constituyentes); Argentina

Probe beam deflection (PBD) techniques, both as cyclic voltadeflectometry (CVD) and chronodeflectometry (CD), were applied for the first time to the study of the electrochemistry of nanostructured Pt materials which are commonly used as electrocatalysts in fuel cells. The electrochemical surface reactions, including faradaic processes, double layer charging and specific anion adsorption were easily detected. Quantitative analysis of the chronodeflectometric data made possible to elucidate the dynamics of double layer charging in such materials and to determine the potential of zero charge (pzc) of the metal present either as a monolithic mesoporous material or as metal nanoparticles supported on carbon. The electro-oxidation of CO, adsorbed on nanostructured Pt, was also studied by CVD and CD being able to detect the formation of CO2 and H3O+ related with the nucleation and growth process which controls the rate of CO stripping. The interplay of Pt oxide formation and COad electrooxidation, both in potential and time, was detected indicating possible application of the technique to other electrocatalysts.

Small atomic gold clusters in solution, Au n , stabilized by tetrabutyl ammonium bromide (TBABr), have been synthesized by a simple electrochemical technique, based on the anodic dissolution of a gold electrode in the presence of TBABr salt, and using acetronitrile as solvent. The presence of clusters in the range Au3-Au11 were detected by MALDI-TOF spectroscopy, and further characterized by UV-vis absorption spectroscopy, TEM, AFM, X-ray diffraction, and cyclic voltammetry. Clusters display a semiconductor behavior with a band edge of approximately 2.5 eV. We report here their extraordinarily high electrocatalytic activity toward the O2 reduction reaction in acid solutions, which can explain Zhang's results, showing that a four-electron mechanism seems to occur because of the facile reduction of H2O2 on gold clusters compared to bulk gold or larger gold nanoparticles.

Probe beam deflection (PBD) and AC impedance are used to quantitatively evaluate the double layer properties of carbon aerogel electrodes in aqueous media (NaF). The measurements allow determination of the potential of minimum charge of the material.

Spectroscopic methods are used to investigate the formation of low molecular mass intermediates during aniline (ANI) oxidation and polyaniline (PANI) degradation. Studying ANI anodic oxidation by in situ Fourier transform infrared spectroscopy (FTIRS) it is possible to obtain, for the first time, spectroscopic evidence for ANI dimers produced by head-to-tail (4-aminodiphenylamine, 4ADA) and tail-to-tail (benzidine, BZ) coupling of ANI cation radicals. The 4ADA dimer is adsorbed on the electrode surface during polymerization, as proved by cyclic voltammetry of thin PANI films and its infrared spectrum. This method also allows, with the help of computational simulations, to assign characteristic vibration frequencies for the different oxidation states of PANI. The presence of 4ADA retained inside thin polymer layers is established too. On the other hand, FTIRS demonstrates that the electrochemically promoted degradation of PANI renders p-benzoquinone as its main product. This compound, retained inside the film, is apparent in the cyclic voltammogram in the same potential region previously observed for 4ADA dimer. Therefore, applying in situ FTIRS is possible to distinguish between different chemical species (4ADA or p-benzoquinone) which give rise to voltammetric peaks in the same potential region. Indophenol and CO(2) are also detected by FTIRS during ANI oxidation and polymer degradation. The formation of CO(2) during degradation is confirmed by differential electrochemical mass spectroscopy. To the best of our knowledge, this is the first evidence of the oxidation of a conducting polymer to CO(2) by electrochemical means. The relevance of the production of different intermediate species towards PANI fabrication and applications is discussed.

Novel synthetic methods of PANI functiooalization are described. We investigated coupling of diazonium salt and electrophilic nitration of the aromatic ring, amine group protection by amide formation, nucleophilic reaction with activated aromatic moieties and nucleophilic addition of sulfite ions to the ring. The structure of the products and their properties were studied by FTIR, UV-vis spectroscopy and electrochemistry.

Probe beam deflection during chronoamperometric oxidation-reduction of osmium complex in layer-by-layer self-assembled redox active polyelectrolyte multilayers has shown that the nature of the charge in the topmost layer determines the ion flux that balances the redox charge.