Certain specific electrochemical behaviour of some aldehydes. Potentiodynamic investigations

Abstract

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 adsorption and desorption peaks in cyclic voltammograms and provides rather high (over 90 percent) current efficiencies at remarkably high current densities (even above 10 mA cm(-2)) for corresponding alcohol yields; and (b) anodic oxidation of the aldehyde group by its specific electrode reaction mechanism suppresses and even prevents any surface oxide growth at noble metal substrates, and thereby creates a new reverse current jump in the anodic range of repeated aldehyde oxidation within the same cycle during the reversal potential scan towards the hydrogen evolution limits. For various aldehydes, including monosaccharides, the surface oxide desorption peak clearly depends in its charge capacity on the rate of oxidation of the aldehyde groups for each individual reactant and/or the number of adsorbed aldehyde groups per unit area of the electrode surface: the smallest was in the presence of formaldehyde, the largest with d-fructose.