CERTAIN SPECIFIC ELECTROCHEMICAL-BEHAVIOR OF SOME ALDEHYDES - POTENTIODYNAMIC INVESTIGATIONS

Two distinct specific features have been clearly observed and recorded by cyclic voltammetry in alkaline aldehyde (typical simple aldehydes and monosaccharides) solutions: (a) Heterogeneous reaction of aldehyde group hydrogenation at its higher concentrations removes hydrogen ads orption and desorption peaks in cyclic voltammograms and provides rath er high (over 90 percent) current efficiencies at remarkably high curr ent densities (even above 10 mA cm(-2)) for corresponding alcohol yiel ds; and (b) anodic oxidation of the aldehyde group by its specific ele ctrode reaction mechanism suppresses and even prevents any surface oxi de growth at noble metal substrates, and thereby creates a new reverse current jump in the anodic range of repeated aldehyde oxidation withi n the same cycle during the reversal potential scan towards the hydrog en evolution limits. For various aldehydes, including monosaccharides, the surface oxide desorption peak clearly depends in its charge capac ity on the rate of oxidation of the aldehyde groups for each individua l reactant and/or the number of adsorbed aldehyde groups per unit area of the electrode surface: the smallest was in the presence of formald ehyde, the largest with d-fructose.