Ethanol oxidation has been studied on Pt(111), Pt(100) and Pt(110) electrodes in order to investigate the effect of the surface structure and adsorbing anions using electrochemical and FTIR techniques. The results indicate that the surface structure and anion adsorption affect significantly the reactivity of the electrode. Thus, the main product of the oxidation of ethanol on the Pt(111) electrode is acetic acid, and acetaldehyde is formed as secondary product. Moreover, the amount of CO formed is very small, and probably associated with the defects present on the electrode surface. For that reason, the amount of CO2 is also small. This electrode has the highest catalytic activity for the formation of acetic acid in perchloric acid. However, the formation of acetic acid is inhibited by the presence of specifically adsorbed anions, such as (bi)sulfate or acetate, which is the result of the formation of acetic acid. On the other hand, CO is readily formed at low potentials on the Pt(100) electrode, blocking completely the surface. Between 0.65 and 0.80 V, the CO layer is oxidized and the production of acetaldehyde and acetic acid is detected. The Pt(110) electrode displays the highest catalytic activity for the splitting of the C-C bond. Reactions giving rise to CO formation, from either ethanol or acetaldehyde, occur at high rate at any potential. On the other hand, the oxidation of acetaldehyde to acetic acid has probably the lower reaction rate of the three basal planes.

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Ethanol oxidation has been studied on stepped platinum single crystal electrodes in acid media using electrochemical and Fourier transform infrared (FTIR) techniques. The electrodes used belong to two different series of stepped surfaces: those having (111) terraces with (100) monoatomic steps and those with (111) terraces with (110) monoatomic steps. The behaviors of the two series of stepped surfaces for the oxidation of ethanol are very different. On the one hand, the presence of (100) steps on the (111) terraces provides no significant enhancement of the activity of the surfaces. On the other hand, (110) steps have a double effect on the ethanol oxidation reaction. At potentials below 0.7 V, the step catalyzes the C-C bond cleavage and also the oxidation of the adsorbed CO species formed. At higher potentials, the step is not only able to break the C-C bond, but also to catalyze the oxidation of ethanol to acetic acid and acetaldehyde. The highest catalytic activity from voltammetry for ethanol oxidation was obtained with the Pt(554) electrode.

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The adsorption and oxidation of oxalic acid at gold electrodes were studied by in-situ infrared spectroscopy. External reflection experiments carried out with gold single-crystal electrodes were combined with internal reflection (ATR-SEIRAS) experiments with gold thin-film electrodes. These gold thin films, with a typical thickness of ca. 35 nm, were deposited on silicon substrates by argon sputtering. As previously reported for evaporated gold films, the voltammetric curves obtained in sulfuric acid solutions after electrochemical annealing show typical features related to the presence of wide bidimensional (111) domains with long-range order. The in-situ infrared data collected for solutions of pH 1 confirmed the potential-dependent adsorption of either oxalate (Au(100)) or a mixture of bioxalate and oxalate (Au(111), Au(110), and gold thin films) anions in a bidentate configuration. The better signal-to-noise ratio associated with the SEIRA effect in the case of the gold thin-film electrodes allows the observation of the carbonyl band for adsorbed bioxalate that was not detected in the external reflection experiments. Besides, additional bands are observed between 2000 and 3000 cm(-)(1) that can be tentatively related to the formation of hydrogen bonds between neighboring bioxalate anions. The intensities of these bands decrease with increasing solution pH values, disappearing for pH 3 solutions in which adsorbed oxalate anions are the predominant species. The analysis of the intensities of the nu(s)(O-C-O) and nu(C-OH) + delta(C-O-H) bands for adsorbed oxalate and bioxalate, respectively, suggests that the pK(a) for the surface equilibrium between these species is significantly lower than that for the solution equilibrium.

Oxidation of ethanol on ruthenium-modified Pt(775) and Pt(332) stepped electrodes has been studied using electrochemical and FTIR techniques. It has been found that the oxidation of ethanol on these electrodes takes place preferentially on the step sites yielding CO(2) as the major final product. The cleavage of the C-C bond, which is the required step to yield CO(2), occurs only on this type of site. The presence of low ruthenium coverages on the step sites promotes the complete oxidation of ethanol since it facilitates the oxidation of CO formed on the step from the cleavage of the C-C bond. However, high ruthenium coverages have an important inhibiting effect since the adatoms block the step sites, which are required for the cleavage of the C-C bond. Under these conditions, the oxidation current diminishes and the major product in the oxidation process is acetic acid, which is the product formed preferentially on the (111) terrace sites.

Down to the wire: electro‐active bacteria that exchange electrons with solid electrodes are studied by electrochemical and infrared techniques. The approach allows the identification of cell‐surface molecules involved in the direct electron transfer to the electrode, a development that is crucial for future utilization of these electricity‐producing microorganisms.

Understanding the structure and molecular processes at the electrode/membrane interfaces constitutes an important topic in PEFC as well as in electrochemistry. In this work, the Pt(111)/Nafion model interface in HClO 4 acid solutions is studied by IRRAS and cyclic voltammetry. It was found that the presence of an electric field mainly promotes deprotonation of sulfonic groups and structuring of water inside the membrane (polar molecules), especially near the electrode surface, with a sudden change of system optical properties at the Pt(111)/membrane interface at 0.9 V, possibly due to clustering within the polymer. Furthermore, the performance of the Pt(111)/Nafion in a typical electrochemical reaction as CO oxidation has been also analyzed. It is shown that there are notable differences between the characteristics of CO adsorption and oxidation at Pt( 111) with and without polymer electrolyte membrane, like a continual wavenumber increase with the potential for the on-top CO band, even during CO oxidation, which proceeds at higher potentials at the electrode covered by the polymer. The spectroscopic features suggest enhanced proton mobility inside the membrane concomitantly with the deprotonation of sulfonic groups near the electrode surface and with higher potentials, possibly due to oriented morphologies inside the membrane induced by high fields.