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The anodic oxidation of NHzOH on Pt in neutral and acid solutions was studied using CV, RRDE and Mass Spectroscopic Cyclic Voltammetry. Thus, the i/rfJ-curves obtained could be correlated to the rates of formation of the gaseous products N z, NzO, NO and NO z. Three anodic waves were distinguished, each representing 2e-processes as concluded from the products NOH, NOi and N0 3 -belonging to the respective wave. NO is a side product formed by anodic oxidation of NOH within the raising part of the second wave. A detailed mechanism is proposed on the basis of these findings.

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Nitrobenzene / p-Benzoquinone / Li+-cations / Carbon fibre electrodes / Acetonitrile / DimelhylformamideThe electrochemical behavior of nitrobenzene and p-benzoquinone in acetonitrile and dimethylformamide and the influence of the Li """-cations on the reduction of these depolarizers are investigated on carbon fibre electrodes.When Et4NC104 is used as the supporting electrolyte the corresponding radical anion is formed in all cases as the primary reduction product; the radical anion is further reduced to the final product at higher negative potentials.The introduction of small amounts of LiC104 leads to the formation of ion pairs between the radical anion and the Li+-cations, which produce a significant shift of both reduction waves to higher positive potentials. These effects are more pronounced in acetonitrile, where the ion pairs formed take the additional electrons during a succeeding fast heterogeneous process; consequently only one reduction peak is observed, i.e. the over all reduction of the substrates investigated is substantially facilitated in the presence of the Li+-cations.Das elektrochemische Verhalten von Nitrobenzol und /j-Benzochinon in Acetonitril und Dimethylformamid und die Wirkung der Li """-Kationen auf die Reduktion dieser Depolarisatoren werden an Kohlenstoff-Faser-Elektroden untersucht.Bei der Verwendung von Et4NC104 als Leitsalz bildet sich in allen Fällen das entsprechende Radikalanion als das Primärprodukt der Reduktion, welches bei viel negativeren Potentialen die zu seiner völligen Reduktion benötigten übrigen Elektronen aufnimmt.In Gegenwart von kleinen LiC104-Mengen entstehen zwischen dem Radikalanion und den Li+-Kationen Ionenpaare, die eine erhebliche Verschiebung beider Reduktionsstufen zu positiveren Potentialen bewirken. Ausgeprägter sind die Effekte in Acetonitril, wo die sich bildenden Ionenpaare in einem rasch ablaufenden heterogenen Folgeprozeß die übrigen Elektronen aufnehmen, so daß nur eine Reduktionsstufe in Erscheinung tritt und somit die ganze Reduktion wesentlich erleichtert wird.

ChemInform Abstract from 0.5 M H2SO4 solution is studied using cyclic voltammetry, chronoamperometry, and chronopotentiometry combined with SEM observation. Pt4+ is reduced at the C-fibers, produced by graphitization of polyacrylonitrile, in two well-defined two-electron irreversible steps. The deposition mechanism involves instantaneous nucleation with hemispherical growth. The Pt deposits from acid solutions are firmly attached on the fibers, exhibiting their catalytic activity for H2 and O2 evolution even at low surface concentrations.