Following the discovery of electronic conductivity in doped polyacetylene, various studies on conducting polymers have been investigated. These polymers are essentially characterized by the presence of conjugated bonding on polymer backbone, which facilitates formation of polarons and bipolarons as charge carriers. Poly(3,4-ethylenedioxythiophene) (PEDOT) is an interesting polymer because of high electronic conductivity, ease of synthesis and high chemical stability. Electrochemically prepared PEDOT is more interesting than the polymer prepared by chemical routes because it adheres to the electrodes surface and the PEDOT coated electrodes can directly be used for various applications such as batteries, supercapacitor, sensors, etc. A majority of the studies described in the thesis are based on PEDOT. Studies on polyanthanilic acid and reduction of hydrogen peroxide on stainless steel substrate are also included. Chapter 1 provides an introduction to conducting polymers with a focus on synthesis, electrochemical characterization and applications of PEDOT. In Chapter 2, microscopic and impedance spectroscopic characterization of PEDOT coated on stainless steel (SS) and indium tin oxide (ITO) coated glass substrates are described. Electrosynthesis of PEDOT is carried out on SS electrodes by three different techniques, namely, potentiostatic, galvanostatic and potentiodynamic techniques. The SEM images of PEDOT prepared by the galvanostatatic and potentiostatic routes indicate globular morphology. However, it is seen that porosity increases by increasing the current or the potential. In the cases of both galvanostatic and potentiostatic routes, the oxidation of EDOT to form PEDOT takes place continuously during preparation. However, in the case of potentiodynamic experiment between 0 and 0.9 V vs. SCE (saturated calomel electrode), the formation of PEDOT occurs only when the potential is greater than 0.70 V. During multicycle preparation to grow thicker films of PEDOT, formation of PEDOT takes place layer by layer, a layer of PEDOT being formed in each potential cycle. PEDOT prepared in the potential ranges 0-0.90 V and 0-1.0 V show globular morphology similar to the morphology of the galvanostatically and potentiostatically prepared polymer. If prepared in the potential ranges 0-1.1 V and 0-1.2 V, the PEDOT films have rod-like and fibrous morphology. This is attributed to larger amount of PEDOT formed in each cycle in comparison with lower potential ranges and also to partial oxidation of PEDOT at potentials ≥ 1.10 V. PEDOT is also electrochemically prepared on ITO coated glass substrate. Preparation is carried out under potentiostatic conditions in the potential range between 0.9 and 1.2 V. Atomic force microscopy (AFM) studies indicate a globular topography for PEDOT films prepared on ITO coated glass plates. The height and width of globules increase with an increase in deposition potential. The PEDOT coated SS electrodes are subjected to electrochemical impedance spectroscopy studies in 0.1 M H2SO4. The Nyquist plot of impedance consists of a depressed semicircle, which arises due to a parallel combination of the polymer resistance and double-layer capacitance (Cdl). Impedance data are analyzed. Studies on electrooxidation of methanol, formic acid, formaldehyde and ethanol on nanocluster of Pt and Pt-Ru deposited on PEDOT/C electrode are reported in Chapter 3. Studies on electrooxidation of small molecules are important in view of their promising applications in fuel cells. Films of PEDOT are electrochemically deposited on carbon paper. Nanoclusters of Pt and bimetallic Pt-Ru catalysts are potentiostatically deposited on PEDOT/C electrodes. Catalysts are also prepared on bare carbon paper for studying the effect of PEDOT. The presence of PEDOT film on carbon paper allows the formation of uniform, well dispersed nanoclusters of Pt as well as Pt-Ru catalysts. TEM studies suggest that the nanoclusters of about 50 nm consist of nanoparticles of about 5 nm in diameter. Electrooxidation of methanol, formic acid, formaldehyde and ethanol are studied on Pt-PEDOT/C and PtRu-PEDOT/C electrodes by cyclic voltammetry and chronoamperometry. The data for oxidation of these small organic molecules reveal that PEDOT imparts a greater catalytic activity for the Pt and Pt-Ru catalysts. Results of these studies are described in Chapter 3. In Chapter 4, PEDOT is coated on SS substrate to investigate phenol oxidation. Studies on electrochemical oxidation of phenol are interesting because it is important to remove phenol from contaminated water or industrial effluents. Deactivation of the anode due to the formation and adsorption of polyoxyphenylene on its surface is a common problem for a variety of electrode materials, during phenol oxidation. Investigations on suitable anode materials, which can undergo no or moderate poisoning by polyoxyphenylene, are interesting. In the present study, it is shown that the electrooxidation rate of phenol is greater on PEDOT/SS electrodes than on Pt. Deactivation of PEDOT/SS electrode is slower in relation to Pt. The oxidation of phenol on PEDOT/SS electrode occurs to form both polyoxyphenylene and benzoquinone in parallel. Cyclic voltammetry of phenol oxidation is studied by varying the concentration of phenol, sweep rate and thickness of PEDOT. Ac impedance studies indicate a gradual increase in polymer resistance due to adsorption of polyoxyphenylene during multi sweep cyclic voltammetry. This investigation reveals that PEDOT coated on a common metal or alloy such as SS is useful for studying electrooxidation of phenol, which is generally studied on a noble metal based electrodes. Electrochemically prepared PEDOT is used for supercapacitor studies and the results are presented in Chapter 5. Generally, electronically conducting polymers possess high capacitive properties due to pseudo-faradaic reactions. PEDOT/SS electrodes prepared in 0.1 M H2SO4 are found to yield higher specific capacitance (SC) than the electrodes prepared from neutral aqueous electrolyte. The effects of concentration of H2SO4, concentration of SDS, potential of deposition and nature of supporting electrolytes used for capacitor studies on SC of the PEDOT/SS electrodes are studied. Specific capacitance values as high as 250 F g-1 in 1 M oxalic acid are obtained during the initial stages of cycling. However, there is a decrease in SC on repeated charge-discharge cycling. Spectroscopic data reflect structural changes in PEDOT on extended cycling. Self-doped PANI is expected to possess superior electrochemical characteristics in relation to PANI. The self-doping is due to the presence of an acidic group on the polymer chain. However, self-doped PANI is soluble in acidic solutions against insolubility of PANI. In the present study, poly(anthranilic acid), PANA, is encapsulated in porous Nafion membrane by chemical and a novel electrochemical methods. PANA present in solid form in Nafion membrane does not undergo dissolution in acidic solutions. The methods of preparation and various electrochemical, optical and spectroscopic characterizations studies of PANA-Nafion are described in Chapter 6. Electroreduction of H2O2 is studied on sand-blasted stainless steel (SSS) electrode in an aqueous solution of NaClO4 and the details are reported in Chapter 7. The cyclic voltammetric reduction of H2O2 at low concentrations is characterized by a cathodic peak at -0.40 V versus standard calomel electrode (SCE). Cyclic voltammetry is studied by varying the concentration of H2O2 in the range from 0.2 mM to 20 mM and the sweep rate in the range from 2 to 100 mV s-1. Cyclic voltammograms at concentrations of H2O2 higher than 2 mM or at high sweep rates consist of an additional current peak, which may be due to the reduction of adsorbed species formed during the reduction of H2O2. Amperometric determination of H2O2 at -0.50 V vs. SCE provides the detection limit of 5 μM H2O2. A plot of current density versus concentration has two linear segments suggesting a change in the mechanism of H2O2 reduction at concentrations of H2O2 ≥ 2 mM. From the rotating disc electrode study, diffusion co-efficient of H2O2 and rate constant for reduction of H2O2 are evaluated. Thus, stainless steel, which is inexpensive and a common alloy, is useful for studying electrochemical reduction of H2O2 and also for analytical application. This work is initiated to study the reduction of H2O2 on PEDOT/SS electrodes. As a result of preliminary experiments, it is found that PEDOT does not exhibit any influence on the kinetics of H2O2 reduction. Therefore studies conducted using bare stainless steel are included in this chapter. Results of the above studies are described in the thesis.

Este trabalho investigou a oxidação eletroquímica do ácido tânico em eletrodos do tipo Ânodo Dimensionalmente Estáveis (ADE) a base de SnO2 e IrO2 e eletrodos de Diamante Dopado com Boro (BDD). As eletrólises foram feitas em modo galvanostático em função de parâmetros como densidade de corrente e concentração de cloreto. A oxidação eletroquímica do ácido tânico foi capaz de promover a diminuição da concentração de fenóis totais, Carbono Orgânico Total (COT) e Demanda Química de oxigênio (DQO). Para os ADE os melhores resultados de remoção de Carbono Orgânico Total (COT) foram nas condições em que se utilizou 300 mg L-1 de cloreto e densidade de corrente de 25 mA cm-2. No entanto houve a formação de compostos organoclorados que não foram degradados com maiores tempo de reação. Para os eletrodos de BDD, obteve-se a remoção de aproximadamente 98% de COT após 10 horas de reação à 75 mA cm-2, na ausência de cloreto. Maiores remoções de COT são obtidas com o aumento da densidade de corrente. Eletrólises na presença de cloreto removeram quase 100% do COT em tempos menores de reação. Análises de compostos organohalogenados (AOX) mostraram que não houve a formação de compostos organoclorados. Menores densidades de corrente apresentaram maiores Eficiência de Corrente (EC) e menor Consumo de Energia (CE). As eletrólises na presença de cloro apresentaram melhores resultados de EC que na ausência do mesmo. A oxidação fotoeletroquímia do ácido tânico em eletrodos do tipo ADE de composição nominal Ti/ Sn0,7 Ir0,3 O2 também foi investigada nesse trabalho. O tratamento fotoeletroquímico foi realizado utilizando uma lâmpada de vapor de mercúrio de alta pressão de 125 W como fonte de irradiação. A variação da corrente não mostrou diferença significativa na oxidação do ácido tânico. A variação da concentração de cloreto no eletrólito suporte influenciou de forma acentuada a oxidação do ácido tânico. O tratamento fotoeletroquímico se mostrou mais eficiente na remoção de COT que os tratamentos eletroquímico e fotoquímico. No tratamento fotoeletroquímico ocorreu a formação de AOX no início da reação, no entanto com o passar do tempo esses compostos foram degradados. / This study investigated the electrochemical oxidation of tannic acid on electrodes of the Dimensionally Stable Anode (DSA) type based on SnO2 and IrO2 as well as on boron doped diamond (BDD) electrodes. The electrolyses were performed in the galvanostatic mode, as a function of such parameters as current density and chloride concentration. The electrochemical oxidation of tannic acid was able to promote the reduction of the concentration of total phenolics, total organic carbon (TOC), and chemical oxygen demand (COD). For the DSA the best results of Total Organic Carbon (TOC) removal were achieved at 300 ppm chloride and current density of 25 mA cm-2. However, organochlorine compounds were formed and were not degraded with increased reaction times. For the BDD electrodes, the removal of approximately 98% TOC was obtained after 10 hours of reaction at 75 mA cm-2, in the absence of chloride. Major TOC removals were obtained with increasing current density. Electrolyses in the presence of chloride removed almost 100% TOC in shorter reaction times. Analysis of organohalogen compounds (AOX) showed no formation of organochlorine compounds. Lower current densities led to higher current efficiency (CE) and lower Energy Consumption (EC). The electrolyses in the presence of chlorine produced better CE results than those performed in the absence of chlorine. The photoelectrochemical oxidation of tannic acid in ADE-type electrodes of nominal composition Ti / Sn0.9 Ir0.3 O2 was also investigated in this work. The photoelectrochemical treatment was performed using a high pressure mercury vapor lamp 125 W as the source of irradiation. The variation in current revealed no significant difference in the oxidation of tannic acid. The variation in chloride concentration in the electrolyte markedly influenced the oxidation of tannic acid. The photoelectrochemical treatment was more efficient for TOC removal than the electrochemical and photochemical treatments. Formation of AOX occurred at the beginning of the photoelectrochemical treatment, but over time these compounds were degraded.

A eletrooxidação de etanol foi investigada sobre catalisadores bi e trimetálicos constituídos de Pt-M1 e Pt-M-M1 M = Sn, Mo, W, Ru, Os e Ir). Os eletrodos foram preparados em três diferentes configurações: eletrodos lisos (preparados em forno a arco voltaico), filmes depositados em placas de Ti (Pt-M/Ti) e nanopartículas metálicas dispersas em carbono (Pt-M-M1/C), ambos preparados pelo método Pechini. Os resultados eletroquímicos mostraram que a adição dos diferentes metais à platina aumentou a atividade catalítica dos eletrodos. Este efeito se mostrou dependente da composição do eletrodo e para os eletrodos lisos apresentou resultados mais acentuados nas composições Pt-Os e Pt-Sn-W. Os intermediários e produtos de reação da oxidação de etanol os eletrodos lisos foram determinados pelas técnicas de FTIR in situ de SPAIRS e SNIFTIRS. Os resultados sugerem que a presença dos elementos modificadores da platina aumentam a velocidade da reação de oxidação de etanol pela dessorção de intemediários com dois átomos de carbono (como CH3CHOads) a potenciais mais baixos do que a Pt levando conseqüentemente a liberação dos sítios ativos para nova adsorção de etanol. Constatou-se contudo, que a presença desses elementos não favorece a quebra da ligação C-C para formação de CO2 em quantidades apreciáveis. As composições de catalisadores Pt-M/Ti (M = Sn, Ru, Ir e Mo) preparados pelo método Pechini que apresentaram os melhores resultados em densidades de corrente foram os eletrodos de Pt-Sn/Ti. As análise por HPLC mostraram o produto majoritariamente formado foi o acetaldeído independente da composição do catalisador, mas os catalisadores Pt-Sn/Ti tiveram a maior seletividade na formação de ácido acético. Os testes em célula unitária foram realizados para os catalisadores trimetálicos Pt-Sn-W/C em diferentes composições. A presença de Sn e W aumentou significativamente o desempenho da célula com relação à Pt pura. O melhor catalisador testado (Pt-Sn-W/C (85:8:7)) apresentou OCV de 777 mV contra 345 mV da Pt a 90oC. A densidade de potência máxima alcançada para essa composição foi de 33 mW cm-2. A análise de produtos ao final de 5 horas de reação a 90oC aplicando 30 mA cm-2 de corrente mostrou que os produtos principalmente formados foram ácido acético e acetaldeído. / Ethanol oxidation on Pt-M1 e Pt/M/M1 (M = Sn, Mo, W, Ru, Os e Ir) catalysts prepared by arc melting furnace process and Pechini method was investigated. The electrochemical data showed that the addition of these elements to Pt gives a highest current densities at lower potentials. The best composition of electrodes prepared by arc melting process based on current densities values was Pt-Os and Pt-Sn-W. The intemediates and reaction products for ethanol oxidation were detected by SPAIRS and SNIFTIRS. The results sugest that adding a foreign metal to Pt leads an increase of the reaction rate for ethanol oxidation because desorption of two carbon atoms intermediates (as CH3 CHOads) at lower potentials comparing to pure Pt. The active site become then available for the new ethanol adsorption. However, the presence of these metals doesn\'t increase the selectivity to CO2 generation. Pt-M/Ti (M = Sn, Ru, Ir e Mo) catalysts were prepared by Pechini method. The products of the ethanol oxidation on these electrodes were evaluated by HPLC. The results showed that acetaldehyde was the main product obtained for all compositions. DEFCs tests were carry on with Pt-Sn-W/C ternary catalysts in different compositions. It was obtained particles size about 3.9 to 11 nm, depending on the catalyst composition. The addition of Sn and W increased significantly the DEFC performance. The best result was obtained by Pt-Sn-W/C (85:8:7) catalyst. It presents OCV about 777 mV against 345 mV to Pt at 90oC. The maximum of power density for this catalyst was 33 mW cm-2. Acetaldehyde was the major product formed when applying a fixed current of 30 mA cm-2 at 90oC.

Este trabalho descreve estudos eletroquímicos e espectroscópicos da eletrooxidação de etanol, acetaldeído e ácido acético sobre uma superfície de platina monocristalina de baixo índice de Miller 110 modificada por ósmio (Os). O eletrodo monocristalino de Pt(110) foi modificado por Os espontaneamente e pela aplicação de potencial. Os eletrodos foram caracterizados eletroquimicamente, de forma que foram obtidos valores baixos, intermediários e altos de Os sobre a superfície de Pt(110). A eletrooxidação de etanol sobre Pt(110) e Pt(110)/Os, analisada pelas técnicas de voltametria cíclica e cronoamperometria, mostrou que as densidades de corrente para essa reação foram maiores nos graus de recobrimento entre 0,51 – 0,61 ML. A partir dos resultados de FTIR in situ, verificou-se que a reação de oxidação de etanol difere em seus caminhos de acordo com o grau de recobrimento de Os. O caminho um sugere a quebra da ligação C—C com maior intensidade em graus de recobrimento entre 0,36 – 0,80 ML, formando espécies como COlinear, CHx e, posteriormente, CO2. O caminho dois mostra a formação de acetaldeído a partir de 0,4 V sobre os eletrodos Pt(110) e Pt(110)/Os, e que pode haver ainda a produção de CO e ácido acético a partir desse orgânico sobre eletrodos com HOs > 0,80 ML, a baixos potenciais. O estudo realizado com acetaldeído mostrou que o desempenho na oxidação desse orgânico foi sutilmente maior para os eletrodos modificados por Os. O caminho três apresenta a produção de CO2 proveniente da oxidação de etanol diretamente a ácido acético sobre eletrodos com alto grau de recobrimento. Durante a oxidação ocorre a formação a baixos potenciais de COlinear em grandes quantidades. Além disso, há produção de ácido acético e posteriormente de CO2. Ainda nos eletrodos espessos, a produção de CO2 ocorre sem que se observe a presença de COlinear, indicando a possibilidade da oxidação de ácido acético a CO2. A eletrooxidação de ácido acético sobre os diversos eletrodos de Pt(110)/Os mostra que ocorre a quebra dessa molécula para formar CO2, embora de forma menos expressiva que as demais moléculas estudadas. Sendo que parte do CO2 produzido provavelmente tem sua origem no grupo COO- que está adsorvido sobre a superfície do eletrodo. / This work reports the electrochemical and spectroscopic results of ethanol, acetaldehyde and acetic acid electrooxidation onto low index platinum single crystal surface (110) modified by osmium (Os). The Pt(110) electrode was modified by spontaneous and electroless Os deposition and checked electrochemically in order to obtain low, intermediate and high Os coverages on Pt(110). The ethanol electrooxidation on Pt(110) and Pt(110)/Os, which used voltammetric cycle and cronoamperometric techniques, showed higher currents toward this reaction on Os coverage between 0.51-0.61 ML. The FTIR results reveal that ethanol oxidation has different pathways according to Os coverage. The step one suggests that the cleavage of ethanol C—C bond occurs with major intensity forming species such as COlinaer and CHx when the reached coverage is 0.36 – 0.80 ML and further producing CO2. At the step two, acetaldehyde formation is improved above 0.4 V on Pt(110) and Pt(110)/Os, and at low potentials on HOs > 0.80 ML, this molecule can oxidize and form CO and acetic acid. Studies on acetaldehyde showed that the catalytic activity is slightly higher on electrodes modified by Os. The step three presents the CO2 production through acetic acid onto electrodes with high Os coverage. During the oxidation of this molecule, COlinear is produced in large quantities at low potentials; there is formation of acetic acid and thereupon CO2. Onto Os thick electrode, CO2 production occurs without the presence of COlinear, indicating the possibility of acetic acid oxidation directly to CO2. The acetic acid oxidation on various electrodes modified by Os is possible with cleavage of C—C bond to form CO2, though this process is less significant than others organic molecules studied. Since the amount of CO2 produced can arise through the acetate group once this specie is adsorbed onto the electrode surface.

<p>The work described in this thesis aims to achieving surface patterning through chemical activation of thiolated silicon oxide surfaces, resulting in a spatially controlled covalent immobilization of biomolecules with high resolution.</p><p>Existing chemical methods to immobilize molecules on surfaces do not reach below the micrometer scale while the ones allowing for spatial control mostly lead to non-covalent adsorption of molecules on surfaces, or require several successive chemical reactions to obtain the final covalent immobilization. Methods with improved chemical processes and novel surface modification techniques had to be developed. </p><p>A basic need for studying interactions of biomolecules on chemically modified surfaces with high resolution is the ability to obtain a simple, inexpensive method resulting in ultraflat densely packed and reproducible organic monolayers. Therefore, a new method for silicon oxide chemical derivatization, fulfilling these requirements, was developed. </p><p>Thiol derivatized silicon oxide surfaces allow for a diversity of activation reactions to occur, resulting in thiol-disulfide exchange. The electrooxidation of surface-bound thiol groups was investigated as a way of generating reactive thiolsulfinates/thiolsulfonates, by application of a positive potential difference to the silicon surfaces. Peptide molecules containing thiol groups were successfully immobilized to the electroactivated surfaces. In addition, this new chemical activation method offers the possibility to release the bound molecules in order to regenerate the surfaces. Subsequently, the thiolated surfaces can be reactivated for further use.</p><p>Since the activated area depends directly on the size of the electrodes used for the oxidation, nanoscale activation of the thiolated surfaces was performed by use of an AFM tip as counter-electrode. Electrooxidized patterns, with a line width ranging from 70 nm to 200 nm, were obtained. A thiol-rich protein, b-galactosidase, was selectively immobilized onto the electroactivated patterns.</p><p>An electrochemical version of microcontact printing was developed in order to activate large surface areas with micrometer scale patterns. Conductive soft polymer stamps were produced using an evaporated aluminum coating. Patterned electroactivation of thiols was achieved, and polystyrene beads were subsequently specifically immobilized onto the patterns.</p><p>As a conclusion, these different projects resulted in a strategy enabling the achievement of nanoscale and microscale positioning and immobilization of biomolecules on silicon surfaces, with potential reversibility and reuse of the surfaces.</p>

The work described in this thesis aims to achieving surface patterning through chemical activation of thiolated silicon oxide surfaces, resulting in a spatially controlled covalent immobilization of biomolecules with high resolution. Existing chemical methods to immobilize molecules on surfaces do not reach below the micrometer scale while the ones allowing for spatial control mostly lead to non-covalent adsorption of molecules on surfaces, or require several successive chemical reactions to obtain the final covalent immobilization. Methods with improved chemical processes and novel surface modification techniques had to be developed. A basic need for studying interactions of biomolecules on chemically modified surfaces with high resolution is the ability to obtain a simple, inexpensive method resulting in ultraflat densely packed and reproducible organic monolayers. Therefore, a new method for silicon oxide chemical derivatization, fulfilling these requirements, was developed. Thiol derivatized silicon oxide surfaces allow for a diversity of activation reactions to occur, resulting in thiol-disulfide exchange. The electrooxidation of surface-bound thiol groups was investigated as a way of generating reactive thiolsulfinates/thiolsulfonates, by application of a positive potential difference to the silicon surfaces. Peptide molecules containing thiol groups were successfully immobilized to the electroactivated surfaces. In addition, this new chemical activation method offers the possibility to release the bound molecules in order to regenerate the surfaces. Subsequently, the thiolated surfaces can be reactivated for further use. Since the activated area depends directly on the size of the electrodes used for the oxidation, nanoscale activation of the thiolated surfaces was performed by use of an AFM tip as counter-electrode. Electrooxidized patterns, with a line width ranging from 70 nm to 200 nm, were obtained. A thiol-rich protein, b-galactosidase, was selectively immobilized onto the electroactivated patterns. An electrochemical version of microcontact printing was developed in order to activate large surface areas with micrometer scale patterns. Conductive soft polymer stamps were produced using an evaporated aluminum coating. Patterned electroactivation of thiols was achieved, and polystyrene beads were subsequently specifically immobilized onto the patterns. As a conclusion, these different projects resulted in a strategy enabling the achievement of nanoscale and microscale positioning and immobilization of biomolecules on silicon surfaces, with potential reversibility and reuse of the surfaces.

Le développement de générateurs d'énergie pour alimenter des micro-appareils électroniques implantés est devenu une option inéluctable. L'objectif général qui a orienté ces recherches était l'élaboration et les études approfondies des propriétés nanomatériaux métalliques utilisables comme électrocatalyseurs afin de convertir l'énergie chimique en énergie électrique. Les nanomatériaux sont obtenus par la méthode de synthèse : Bromide Anion Exchange (BAE) qui a été scrupuleusement revisitée puis optimisée avec un agent réducteur faible (AA) et fort (NaBH4). Cette voie de synthèse a permis d'obtenir (rendement ≥ 90 %) des matériaux plurimétalliques composés d'or, de platine et de palladium. Un prétraitement des supports commerciaux des nanoparticules a permis d’augmenter leurs surfaces, spécifique et active respectivement de 48 et 120 %. Les études (électro)analytiques ont permis d'identifier les intermédiaires et produits de réaction du combustible. Le glucose s'oxyde sans rupture de la liaison C-C pour donner majoritairement du gluconate avec une sélectivité ≥ 88 %. Les tests réalisés en biopile hybride (cathode enzymatique) indiquent que les catalyseurs Au/C-AA et Au60Pt40/C-NaBH4 sont les meilleures anodes abiotiques (Pmax = 125 µW·cm-2 à 0,4 V). Par ailleurs, les piles sans membrane séparatrice et sans enzyme ont été réalisées avec succès pour activer un stimulateur cardiaque et un système de transmission d'information en mode "Wifi". Ces dispositifs, rapportés pour la première fois, ouvrent une ère nouvelle pour la conception de convertisseurs d'énergie pour alimenter les implants médicaux ou des appareils sans fil de détection et de surveillance. / The development of energy converters to power implanted micro-electronic devices has become a cornerstone item. The whole target which has governed this research was the design of advanced nanostructures metals used as electrocatalysts for converting chemical energy into electrical one. These nanomaterials were obtained by the synthesis method: Bromide Anion Exchange (BAE) that has been carefully revisited and optimized, using a weak reducing agent (AA) and strong one (NaBH4). It allowed to prepare efficiently various plurimetallic nanomaterials composed of gold, platinum and palladium (yield ≥ 90%). A thermal pretreatment of commercial carbon supports of nanoparticles has highly boosted their specific and active surface areas with a gain of 48 and 120%. Based on in situ and ex-situ (electro)analytical methods, the intermediates and final reaction products of the fuel oxidation were identified. Glucose electrooxidation occurs without C-C bond cleavage and gives predominantly gluconate with a selectivity ≥ 88 %. Results from the hybrid biofuel cell tests (with an enzyme as cathode catalyst) indicate that Au/C-AA and Au60Pt40/C-NaBH4 are the best abiotic anodes (Pmax = 125 µW cm-2 at 0.4 V cell voltage). A fuel cell without separating membrane and enzyme has been successfully constructed and used to activate a pacemaker and an information transmission system based on "wireless" mode. These last experiments, reported for the first time as using nanomaterials in membrane-less configuration, open a new approach in the design of advanced energy converters to power medical implants or remote systems for detection and electronic monitoring.

A combinação de célula eletroquímica (EC) com a entrada do equipamento de eletroforese capilar (CE), apesar de recente, tem permitido realizar determinação de ânions radicais; pré-concentração eletroquímica de metais pesados, seguida de redissolução, separação e detecção; bem como monitorar produtos carregados formados por oxidação eletrocatalítica de espécies neutras, como álcoois primários e glicerol. Empregando o sistema EC-CE-C4D desenvolvido pelo grupo, a determinação simultânea de cátions, ânions (no contra fluxo) e espécies neutras (detectadas após derivatização eletroquímica) foi demonstrada pela primeira vez, tendo o antisséptico bucal (Listerine® Tartar Control) como amostra real. Embora constante e reprodutível, a conversão dos álcoois primários nos respectivos carboxilatos apresentou rendimento relativamente baixo, ~16%, nas condições anteriormente adotadas, 1,6 V vs. Ag/AgClKCl 3M empregando eletrodo de platina em meio ácido (HNO3 5 mmol L-1 / HCl 1 mmol L-1). Dessa maneira, avaliou-se a oxidação de álcoois primários de cadeia normal (C2 &#8722; C5) sobre diferentes materiais de eletrodo (ouro e platina) em diferentes meios (ácido, neutro e alcalino). Os carboxilatos gerados foram monitorados injetando uma alíquota da amostra derivatizada no capilar (50 &#181;m d.i., 45 cm de comprimento e 20 cm efetivo) aplicando 5 kPa durante 5 s, e durante as separações, 30 kV foi aplicado entre as extremidades do capilar preenchido com Tris 30 mmol L-1 / HCl 10 mmol L-1 usado como BGE. Os resultados obtidos com o sistema EC-CE-C4D apontaram maior conversão dos álcoois nos respectivos ácidos carboxílicos em meio ácido, tanto em ouro quanto em platina. Adicionalmente, em eletrodo de ouro a formação dos carboxilatos apresentou certa seletividade não observada sobre platina, favorecendo a conversão dos álcoois de cadeia menor. Noutra vertente, buscando atender as necessidades atuais por metodologias que possibilitem monitorar a eletrooxidação do glicerol em reatores eletroquímicos, desenvolveu-se um método que permitiu determinar simultaneamente o glicerol e alguns de seus possíveis produtos de oxidação neutros, como gliceraldeído e dihidroxiacetona, explorando a formação de complexo carregado com borato (presente no BGE composto por H3BO3 60 mmol L-1 / LiOH 30 mmol L-1), além dos produtos ionizáveis (ácidos carboxílicos) que são comumente analisados por CE. O equipamento de CE utilizado, munido de dois detectores C4D, também permitiu avaliar a interação de alguns ácidos carboxílicos com os modificadores de EOF, Polybrene® e CTAB, empregando MES 30 mmol L-1 / His 30 mmol L-1 como BGE. Seguindo a atual tendência à miniaturização de sistemas analíticos, avaliou-se a possibilidade de construir um sistema EC-CE-C4D miniaturizado. Para isso, um novo método para fabricação de microdispositivos em vidro, baseado em ablação a laser de CO2 assistida por parafina, como alternativa aos dispendiosos métodos de corrosão por via úmida foi desenvolvido. Os dispositivos obtidos por esse método apresentaram canais de perfil semicircular, e as dimensões puderam ser controladas variando a potência e/ou a velocidade de ablação do laser. Contudo, pelos desafios ainda encontrados para se construir um sistema EC-CE-C4D completo em substrato de vidro por ablação a laser de CO2, optou-se por iniciar a miniaturização do sistema EC-CE-C4D com um sistema híbrido em que se aproveita as características mais bem definidas e favoráveis dos tubos capilares de sílica fundida usados em CE convencional. Esse sistema permitiu a determinação quantitativa de metanol na presença de alta concentração de etanol, possibilitando, numa primeira aplicação, realizar o monitoramento da quantidade de metanol e etanol nas frações iniciais coletada durante o processo de destilação fracionada na produção de uísque de milho (moonshine) feito em laboratório. Visto a maior seletividade para conversão dos álcoois de cadeia menor obtidas em eletrodo de ouro e meio ácido, esse foi escolhido para a presente aplicação. As condições que apresentaram melhores resultados no sistema híbrido EC-CE-C4D abrangeram diluição de 100 vezes da amostra em HNO3 2 mmol L-1, eletrooxidação a 1,4 V vs. Ag durante 60 s, injeção eletrocinética no capilar mediante aplicação de 3 kV durante 4 s, e a separação dos carboxilatos realizada aplicando 3 kV entre as extremidades do capilar (50 &#181;m d.i., 15 cm de comprimento com 12 cm efetivo), preenchido com CHES 10 mmol L-1 / NaOH 5 mmol L-1, usado como BGE. A análise das primeiras frações destiladas da \"labmade moonshine\" apresentou um aumento na concentração de etanol (variando de ~80 % a ~100 %) e simultâneo decréscimo da concentração de metanol (variando de 4 % a ~0,1 %). Em suma, avançou-se tanto no leque de aplicações da derivatização eletroquímica hifenizada com a eletroforese capilar como na miniaturização da instrumentação analítica para EC-CE-C4D, favorecendo a disseminação dessa poderosa combinação de três técnicas eletroquímicas. / The direct couple of electrochemical cell (EC) with the inlet of the capillary electrophoresis (CE) equipment, recently demonstrated, has allowed the determination of radical anions; to perform electrochemical preconcentration of traces of heavy metals, followed by stripping, injection, separation and detection; and the generation of charged species by electrochemical oxidation of neutral molecules, e.g. primary alcohols and glycerol. Employing the EC-CE-C4D system developed by our group, the simultaneous determination of cations, anions (in the counter EOF mode) and neutral species (after electrochemical derivatization) was demonstrated for the first time and a mouthwash (Listerine® Tartar Control) was used as a real sample. Although constant and reproducible, the conversion of primary alcohols into carboxylates had a low yield (~16%), under the adopted conditions, 1.6 V vs. Ag/AgClKCl 3M using platinum electrode in acid medium (5 mmol L-1 HNO3 / 1 mmol L-1 HCl). Thus, the yield of carboxylates was studied for the oxidation of alcohols (C2 &#8722; C5) on two electrode materials (gold and platinum) in different media (acid, neutral and alkaline). After the electrooxidation step an aliquot of the derivatized sample was automatically injected into the capillary (50 &#181;m i.d., 45 cm in length and 20 cm up to detector) by applying 5 kPa during 5 s. The separation was carried out applying 30 kV between the capillary ends previously filled with 30 mmol L-1 Tris / 10 mmol L-1 HCl BGE. Cyclic voltammograms show higher current density for alcohols oxidation in alkaline medium than in acid one both on gold and platinum electrodes. On the other hand the yields of carboxylic acids were higher in acidic medium. Besides that, only on gold electrode some selectivity for the carboxylate formation was observed favoring the conversion of the short chain alcohols. In order to meet the current needs for methodologies that allow the monitoring of the electrooxidation of glycerol in electrochemical reactors, a method was also developed that allowed the determination of glycerol and some of its possible neutral oxidation products, such as glyceraldehyde and dihydroxyacetone, by exploring the formation of borate complexes (provided in the BGE composed of 60 mmol L-1 H3BO3 / 30 mmol L-1 LiOH), together with ionizable ones like carboxylic acids. The employed CE equipment with two C4D detectors allowed the evaluation of the interaction between some carboxylic acids and the EOF modifiers, Polybrene® and CTAB, using 30 mmol L-1 MES / 30 mmol L-1 His as BGE. Aligned with a current trend of analytical instrumentation, the miniaturized EC-CE-C4D system was attempted. For that, a new method for manufacturing microdevices in glass, based on paraffin-assisted CO2 laser ablation, was developed as an alternative to costly wet-etching methods. The devices obtained by this method presented channels of semicircular profile and the dimensions could be controlled by varying the laser power and/or ablation velocity. Due to remaining challenges in the construction of a complete laser ablated EC-CE-C4D system on glass, a miniaturized system based on a hybrid approach is presented in the thesis, by taking advantage of the more defined and favorable characteristics of the well known fused silica capillary tubes used in CE. This system allowed the quantitative determination of methanol in the presence of high ethanol concentration by taking advantage of the higher yield of short-chain carboxylic acid formation on gold in acidic medium. The first application was the monitoring of the amount of methanol and ethanol in the initial fractions collected during the fractional distillation process in the production of corn whiskey (moonshine) made in the laboratory. The conditions that showed the best results with the hybrid EC-CE-C4D system included a 100-fold dilution of the sample in 2 mmol L-1 HNO3, electrooxidation at 1.4 V vs. Ag for 60 s, electrokinetic injection into the capillary by applying 3 kV for 4 s and separation of the carboxylates carried out under 3 kV between the ends of the capillary (50 &#181;m i.d., 15 cm in length and 12 cm up to detector) previously filled with 10 mmol L-1 CHES / 5 mmol L-1 NaOH, used as BGE. Analysis of the first distilled fractions of labmade moonshine showed an increase in ethanol concentration (ranging from ~ 80% to ~ 100%) and a simultaneous decrease in methanol concentration (ranging from 4% to ~ 0.1%). In short, both the range of applications of electrochemical derivatization hyphenated with capillary electrophoresis as well the miniaturization of analytical instrumentation for EC-CE-C4D were improved, favoring the dissemination of this powerful combination of three electrochemical techniques.

A combinação de célula eletroquímica (EC) com a entrada do equipamento de eletroforese capilar (CE), apesar de recente, tem permitido realizar determinação de ânions radicais; pré-concentração eletroquímica de metais pesados, seguida de redissolução, separação e detecção; bem como monitorar produtos carregados formados por oxidação eletrocatalítica de espécies neutras, como álcoois primários e glicerol. Empregando o sistema EC-CE-C4D desenvolvido pelo grupo, a determinação simultânea de cátions, ânions (no contra fluxo) e espécies neutras (detectadas após derivatização eletroquímica) foi demonstrada pela primeira vez, tendo o antisséptico bucal (Listerine® Tartar Control) como amostra real. Embora constante e reprodutível, a conversão dos álcoois primários nos respectivos carboxilatos apresentou rendimento relativamente baixo, ~16%, nas condições anteriormente adotadas, 1,6 V vs. Ag/AgClKCl 3M empregando eletrodo de platina em meio ácido (HNO3 5 mmol L-1 / HCl 1 mmol L-1). Dessa maneira, avaliou-se a oxidação de álcoois primários de cadeia normal (C2 &#8722; C5) sobre diferentes materiais de eletrodo (ouro e platina) em diferentes meios (ácido, neutro e alcalino). Os carboxilatos gerados foram monitorados injetando uma alíquota da amostra derivatizada no capilar (50 &#181;m d.i., 45 cm de comprimento e 20 cm efetivo) aplicando 5 kPa durante 5 s, e durante as separações, 30 kV foi aplicado entre as extremidades do capilar preenchido com Tris 30 mmol L-1 / HCl 10 mmol L-1 usado como BGE. Os resultados obtidos com o sistema EC-CE-C4D apontaram maior conversão dos álcoois nos respectivos ácidos carboxílicos em meio ácido, tanto em ouro quanto em platina. Adicionalmente, em eletrodo de ouro a formação dos carboxilatos apresentou certa seletividade não observada sobre platina, favorecendo a conversão dos álcoois de cadeia menor. Noutra vertente, buscando atender as necessidades atuais por metodologias que possibilitem monitorar a eletrooxidação do glicerol em reatores eletroquímicos, desenvolveu-se um método que permitiu determinar simultaneamente o glicerol e alguns de seus possíveis produtos de oxidação neutros, como gliceraldeído e dihidroxiacetona, explorando a formação de complexo carregado com borato (presente no BGE composto por H3BO3 60 mmol L-1 / LiOH 30 mmol L-1), além dos produtos ionizáveis (ácidos carboxílicos) que são comumente analisados por CE. O equipamento de CE utilizado, munido de dois detectores C4D, também permitiu avaliar a interação de alguns ácidos carboxílicos com os modificadores de EOF, Polybrene® e CTAB, empregando MES 30 mmol L-1 / His 30 mmol L-1 como BGE. Seguindo a atual tendência à miniaturização de sistemas analíticos, avaliou-se a possibilidade de construir um sistema EC-CE-C4D miniaturizado. Para isso, um novo método para fabricação de microdispositivos em vidro, baseado em ablação a laser de CO2 assistida por parafina, como alternativa aos dispendiosos métodos de corrosão por via úmida foi desenvolvido. Os dispositivos obtidos por esse método apresentaram canais de perfil semicircular, e as dimensões puderam ser controladas variando a potência e/ou a velocidade de ablação do laser. Contudo, pelos desafios ainda encontrados para se construir um sistema EC-CE-C4D completo em substrato de vidro por ablação a laser de CO2, optou-se por iniciar a miniaturização do sistema EC-CE-C4D com um sistema híbrido em que se aproveita as características mais bem definidas e favoráveis dos tubos capilares de sílica fundida usados em CE convencional. Esse sistema permitiu a determinação quantitativa de metanol na presença de alta concentração de etanol, possibilitando, numa primeira aplicação, realizar o monitoramento da quantidade de metanol e etanol nas frações iniciais coletada durante o processo de destilação fracionada na produção de uísque de milho (moonshine) feito em laboratório. Visto a maior seletividade para conversão dos álcoois de cadeia menor obtidas em eletrodo de ouro e meio ácido, esse foi escolhido para a presente aplicação. As condições que apresentaram melhores resultados no sistema híbrido EC-CE-C4D abrangeram diluição de 100 vezes da amostra em HNO3 2 mmol L-1, eletrooxidação a 1,4 V vs. Ag durante 60 s, injeção eletrocinética no capilar mediante aplicação de 3 kV durante 4 s, e a separação dos carboxilatos realizada aplicando 3 kV entre as extremidades do capilar (50 &#181;m d.i., 15 cm de comprimento com 12 cm efetivo), preenchido com CHES 10 mmol L-1 / NaOH 5 mmol L-1, usado como BGE. A análise das primeiras frações destiladas da \"labmade moonshine\" apresentou um aumento na concentração de etanol (variando de ~80 % a ~100 %) e simultâneo decréscimo da concentração de metanol (variando de 4 % a ~0,1 %). Em suma, avançou-se tanto no leque de aplicações da derivatização eletroquímica hifenizada com a eletroforese capilar como na miniaturização da instrumentação analítica para EC-CE-C4D, favorecendo a disseminação dessa poderosa combinação de três técnicas eletroquímicas. / The direct couple of electrochemical cell (EC) with the inlet of the capillary electrophoresis (CE) equipment, recently demonstrated, has allowed the determination of radical anions; to perform electrochemical preconcentration of traces of heavy metals, followed by stripping, injection, separation and detection; and the generation of charged species by electrochemical oxidation of neutral molecules, e.g. primary alcohols and glycerol. Employing the EC-CE-C4D system developed by our group, the simultaneous determination of cations, anions (in the counter EOF mode) and neutral species (after electrochemical derivatization) was demonstrated for the first time and a mouthwash (Listerine® Tartar Control) was used as a real sample. Although constant and reproducible, the conversion of primary alcohols into carboxylates had a low yield (~16%), under the adopted conditions, 1.6 V vs. Ag/AgClKCl 3M using platinum electrode in acid medium (5 mmol L-1 HNO3 / 1 mmol L-1 HCl). Thus, the yield of carboxylates was studied for the oxidation of alcohols (C2 &#8722; C5) on two electrode materials (gold and platinum) in different media (acid, neutral and alkaline). After the electrooxidation step an aliquot of the derivatized sample was automatically injected into the capillary (50 &#181;m i.d., 45 cm in length and 20 cm up to detector) by applying 5 kPa during 5 s. The separation was carried out applying 30 kV between the capillary ends previously filled with 30 mmol L-1 Tris / 10 mmol L-1 HCl BGE. Cyclic voltammograms show higher current density for alcohols oxidation in alkaline medium than in acid one both on gold and platinum electrodes. On the other hand the yields of carboxylic acids were higher in acidic medium. Besides that, only on gold electrode some selectivity for the carboxylate formation was observed favoring the conversion of the short chain alcohols. In order to meet the current needs for methodologies that allow the monitoring of the electrooxidation of glycerol in electrochemical reactors, a method was also developed that allowed the determination of glycerol and some of its possible neutral oxidation products, such as glyceraldehyde and dihydroxyacetone, by exploring the formation of borate complexes (provided in the BGE composed of 60 mmol L-1 H3BO3 / 30 mmol L-1 LiOH), together with ionizable ones like carboxylic acids. The employed CE equipment with two C4D detectors allowed the evaluation of the interaction between some carboxylic acids and the EOF modifiers, Polybrene® and CTAB, using 30 mmol L-1 MES / 30 mmol L-1 His as BGE. Aligned with a current trend of analytical instrumentation, the miniaturized EC-CE-C4D system was attempted. For that, a new method for manufacturing microdevices in glass, based on paraffin-assisted CO2 laser ablation, was developed as an alternative to costly wet-etching methods. The devices obtained by this method presented channels of semicircular profile and the dimensions could be controlled by varying the laser power and/or ablation velocity. Due to remaining challenges in the construction of a complete laser ablated EC-CE-C4D system on glass, a miniaturized system based on a hybrid approach is presented in the thesis, by taking advantage of the more defined and favorable characteristics of the well known fused silica capillary tubes used in CE. This system allowed the quantitative determination of methanol in the presence of high ethanol concentration by taking advantage of the higher yield of short-chain carboxylic acid formation on gold in acidic medium. The first application was the monitoring of the amount of methanol and ethanol in the initial fractions collected during the fractional distillation process in the production of corn whiskey (moonshine) made in the laboratory. The conditions that showed the best results with the hybrid EC-CE-C4D system included a 100-fold dilution of the sample in 2 mmol L-1 HNO3, electrooxidation at 1.4 V vs. Ag for 60 s, electrokinetic injection into the capillary by applying 3 kV for 4 s and separation of the carboxylates carried out under 3 kV between the ends of the capillary (50 &#181;m i.d., 15 cm in length and 12 cm up to detector) previously filled with 10 mmol L-1 CHES / 5 mmol L-1 NaOH, used as BGE. Analysis of the first distilled fractions of labmade moonshine showed an increase in ethanol concentration (ranging from ~ 80% to ~ 100%) and a simultaneous decrease in methanol concentration (ranging from 4% to ~ 0.1%). In short, both the range of applications of electrochemical derivatization hyphenated with capillary electrophoresis as well the miniaturization of analytical instrumentation for EC-CE-C4D were improved, favoring the dissemination of this powerful combination of three electrochemical techniques.

Cette étude traite de la préparation de nanomatériaux à base de palladium et de platine qui ont une morphologie contrôlée, et de la caractérisation de leur activité électrocatalytique vis-à-vis de l'oxydation de l'éthanol, l'éthylène glycol et le glycérol en milieu alcalin. La détermination des différentes propriétés de ces matériaux utilisés comme catalyseurs anodiques a permis la compréhension des étapes clés et l'élucidation des principaux chemins réactionnels impliqués dans la conversion électrochimique de ces alcools utilisables comme combustible dans une pile.Dans ce contexte, ces nanomatériaux ont été synthétisés soit par la méthode d'auto-assemblage électrostatique, soit par la méthode polyol assistée par microondes. Ces méthodes de synthèse chimique choisies car plus adaptées à cette fin, ont permis d'obtenir des nanoparticules de type cœur@coquille dont les atomes de palladium ou de platine sont situés dans la coquille, et le cœur constitué de nickel, ruthénium ou d'étain. Nanomatériaux synthétisés par auto-assemblage électrostatique - Par souci d'économiser les métaux nobles et précieux, sans pour autant perdre en activité, les électrocatalyseurs synthétisés par auto-assemblage électrostatique ont été dispersés dans du carbone Vulcan XC-72R ou déposés sur des Nanotubes de Carbone (NTC) avec un taux de charge métallique de wt. 40%. Les résultats issus des différentes caractérisations physicochimiques ont montré que les matériaux préparés ont des compositions expérimentales (par Spectroscopie de Rayons-X à Dispersion d’Énergie – EDX) similaires aux valeurs nominales ; les paramètres de maille et volume des particule varient légèrement pour les différents matériaux (Microscopie Electronique en Transmission – MET et Diffraction des Rayons X – DRX), mais ont gardé le caractère cristallographique de la structure cubique à faces centrées du palladium et du platine. Les nanoparticules obtenues sont en général de forme sphérique et ont une taille comprise entre 2 et 9 nm ; leur morphologie indique des systèmes très organisés, mais leur structure coeur@coquille n'a pour l'instant pas été formellement déterminée. Des expériences de CO-Stripping ont permis de caractériser électrochimiquement les surfaces actives les matériaux qui ont été synthétisés. Il en résulte leur surface active augmentent de façon très significative des systèmes monométalliques aux électrodes bimétalliques, en particulier les nanocatalyseurs Ru@Pd/NTC et Ni@Pt/NTC qui ont des surfaces spécifiques respectives de 73 et 74 m²g-1Pd/Pt. Concernant l'électrooxydation des alcools en C2 et C3 dans un électrolyte alcalin (1,0 mol L-1 [NaOH] + 0,5 mol L-1 [alcool]), les électrocatalyseurs contenant du platine et déposés sur des nanotubes de carbone ont une meilleure activité électrocatalytique vis-à-vis de l’oxydation du combustible éthylène glycol en termes de densité de courant mesurée à un potentiel de -0,2 V vs. Hg/HgO/OH-. Par exemple, sur l’électrode de composition Ni@Pt/NTC, il a été relevé en début d’expérience de chronoampérométrie une densité de courant de 200 mA mg-1Pt qui a seulement baissé à 180 mA mg-1Pt après une étude qui a duré 90 minutes.Des analyses par chromatographie liquide (CLHP) ont été entreprises pour déterminer les molécules issues de l’oxydation des combustibles susmentionnés. Les taux de conversion de l'éthylène glycol et du glycérol ont respectivement atteint 74 et 58 % après 12 heures d'électrolyse par chronoampérométrie sur les catalyseurs Ru@Pt/NTC et Ni@Pt/NTC. Si l’oxydation du glycérol produit sélectivement des ions formiate et oxalate sur Ru@Pt/NTC, elle conduit majoritairement aux ions tartronate et mesoxalate sur l’électrode Ni@Pt/NTC, révélant ainsi deux chemins réactionnels de la transformation électrochimique du combustible glycérol selon la structure cœur-coquilles du matériau bimétallique. / The present study proposes the synthesis of nanocatalysts based on palladium and platinum with high morphological organization and investigates their catalytic activity for the electrooxidation of ethanol, ethylene glycol, and glycerol in alkaline medium, seeking to understand the steps and mechanisms involved in these reactions. The nanomaterials were synthesized by the electrostatic self-assembly method and by the polyol microwave-assisted method. The goal was to obtain nanoparticles with morphology inspired by the core@shell-type systems, where the shell layer consists of platinum or palladium, and the core contains nickel, ruthenium, or tin. The electrocatalysts synthesized by the electrostatic self-assembly method were supported on Carbon Vulcan XC-72R or Multi-Walled Carbon Nanotubes (MWCNT, metal/carbon = 40:60). Morphology characterization data indicated uniform spherical shape nanoparticles with size ranging between 2 and 9 nm, besides, the specific morphology point to a particular degree of organization. However, the presence of the core@shell-type system was not confirmed through this analysis. CO-Stripping experiments demonstrated that the electrochemically active surface area of the bimetallic systems increased significantly, particularly for the nanocatalysts Ru@Pd/CNT and Ni@Pt/CNT, whose surface areas were 72.8 and 74.1 m²g-1Pd/Pt² respectively. Concerning the electrooxidation of C2 and C3 alcohols in alkaline medium (1.0 mol L-1 NaOH + 0.5 mol L-1 Fuel), M@Pt/CNT systems exhibited higher catalytic activity, especially when employing ethylene glycol as the fuel, which provided the highest catalytic current at constant potential (Eapp = -0.2 V vs. Hg/HgO/OH-). Specifically, the Ni@Pt/CNT nominal composition presented catalytic activity of 180 mA mg-1Pt. Electrochemical conversion studies were performed with the ethyleneglycol-Ru@Pt/CNT and glycerol-Ni@Pt/CNT systems, and after 12 hours of electrolysis, conversion reached values around 74% and 58%, respectively. Concerning the preferential mechanisms for glycerol electrooxidation, evaluated by liquid chromatography analysis, glycerate and tartronate ions were the major intermediates formed. The Ru@Pt/CNT nanocatalyst was selective for formate and oxalate ions. In addition, Ni@Pd/CNT generated mesoxalate ion during the reaction, suggesting a dual pathway for glycerol conversion, via tartronate and/or mesoxalate ions.The nanostructured materials synthesized by the polyol microwave-assisted method were supported on carbon Vulcan XC-72R with 20% wt. metallic loading. Briefly, the metal cores were synthesized separately for successive deposition of the noble metal, by employing the consecutive reductions technique. We investigated the palladium-based bimetallic catalysts, with ruthenium or nickel metallic cores, for the electrooxidation of ethylene glycol (0.1 mol L-1) in alkaline medium (0.1 mol L-1 NaOH). Morphology characterization data indicated that Pd/C catalyst displayed different nanoparticle shapes, and particle size ranged from 3 to 40 nm. Ru@Pd/C and Ni@Pd/C displayed spherical shape with particle size between 2 and 7 nm and between 3 and 10 nm, respectively. Ni@Pd/C exhibited the higher activity towards ethylene glycol oxidation in alkaline medium, reaching values of about 80 mA mg-1Pd at the end of chronoamperometry experiments. Overall, combination of the results obtained by liquid chromatography-mass spectrometry and infrared spectroscopy in situ showed that oxidation of glycolate ion is the limiting step for ethylene glycol conversion in alkaline medium in the presence of palladium-based catalysts. Lower amounts of glycolaldehyde, glyoxylate, and oxalate ions emerged at the end of electrolysis procedure, and no carbonate arose. / O presente estudo tem como objetivo propor a síntese de nanocatalisadores à base de paládio e platina com elevada organização morfológica e investigar a referente atividade catalítica ao promover a eletro-oxidação do etanol, etilenoglicol e glicerol em meio alcalino, buscando assim compreender as etapas e mecanismos envolvidos perante estas reações. Neste contexto, os nanomateriais foram sintetizados pelo método de automontagem eletrostática e pelo método de poliol assistido por micro-ondas. Estas metodologias foram selecionadas a fim de obter nanopartículas com morfologia inspirada em sistemas do tipo core@shell (núcleo@casca), empregando átomos de paládio ou platina localizados na casca sobre núcleos de níquel, rutênio ou estanho. Os eletrocatalisadores sintetizados via automontagem eletrostática foram suportados em Carbono Vulcan XC-72R ou Nanotubos de Carbono de paredes múltiplas, com razão metal:carbono igual a 40:60. As nanopartículas obtidas apresentaram tamanho que variou entre 2-9 nm, formato esférico em quase sua totalidade e morfologia que indicava a presença de um determinado grau de organização; entretanto não foi confirmada a presença de sistemas do tipo core@shell. Experimentos de CO-Stripping demonstraram um aumento significativo da área eletroquimicamente ativa dos sistemas bimetálicos, com destaque para os nanocatalisadores Ru@Pd/NTC e Ni@Pt/NTC que apresentaram valores de 72,8 e 74,1 m² g-1Pd/Pt² respectivamente. Perante a eletro-oxidação dos álcoois C2 e C3 em meio alcalino (1,0 mol L-1 [NaOH] + 0,5 mol L-1 [Combustível]), os sistemas que apresentaram atividade catalítica mais elevada foram M@Pt/NTC, destacando o etilenoglicol como o combustível que propiciou a maior corrente catalítica quando submetido a potencial constante (E = -0,2 V vs. Hg/HgO/OH-). Mais especificamente, a composição Ni@Pt/NTC apresentou ao final dos experimentos de cronoamperometria um valor de atividade catalítica da ordem de 180 mA mg-1Pt. Os estudos de conversão eletroquímica demonstraram que ao empregar os sistemas etilenoglicol-Ru@Pt/NTC e glicerol-Ni@Pt/NTC atinge-se valores de conversão eletroquímica da ordem de 74% e 58%, respectivamente, após 12 horas de eletrólise a potencial controlado. Quanto aos mecanismos preferenciais de eletro-oxidação do glicerol, avaliados empregando análises de cromatografia líquida, foi verificada a formação majoritária dos íons glicerato e tartronato. Pontualmente, o nanocatalisador Ru@Pt/NTC indicou seletividade para a produção de íons formato e oxalato. Contudo, o catalisador Ni@Pd/NTC propiciou a eletrogeração do íon mesoxalato, sugerindo uma rota dupla de conversão do glicerol, via formação de íons tartronato e/ou mesoxalato.Os materiais nanoestruturados sintetizados via metodologia poliol assistida por micro-ondas foram suportados em Carbono Vulcan XC-72R com carga metálica igual a 20%. Especificamente para este caso, foram sintetizados os núcleos metálicos separadamente, para posterior deposição do metal nobre, empregando a técnica de reduções consecutivas. Foram investigados catalisadores bimetálicos à base de paládio, com núcleos de rutênio ou níquel, para promover a eletro-oxidação do etilenoglicol (0,1 mol L-1) em meio alcalino (0,1 mol L-1 NaOH). As nanopartículas de Pd/C apresentaram diferentes formatos e intervalo de tamanho entre 3-40nm. Para os catalisadores Ru@Pd/C e Ni@Pd/C foram verificados sistemas esféricos com variação do tamanho de partículas entre 2-7 nm e 3-10 nm, respectivamente. Os nanomateriais de composição nominal Ni@Pd/C exibiram elevada atividade para oxidar as moléculas de etilenoglicol em meio alcalino, atingindo valores da ordem de 80 mA mg-1Pd ao final dos experimentos de cronoamperometria.