Adsorption behavior of 1-adamantanecarboxylic acid and its effect on the electroreduction of anions in solutions of different pH

Effect of solution pH on the adsorption behavior of 1-adamantanecarboxylic acid (1-AdCOOH), which forms at the interface electrode/solution two-dimens ional condensed layer, is studied along with the acid's effect on electrore duction of the S2O82- and BrO4- anions. When recording the potential depend ences of the differential capacitance, it is found that, in the pH interval 4.0-6.2, at a constant concentration of 1-AdCOOH, a transition is observed from a complete coverage of the surface by a condensed layer to disappeara nce at relatively high pH values of effects that are typical for a two-dime nsional condensation of organic compounds. Correspondingly, in this pH inte rval, a transition takes place from a strong inhibition of processes of the electroreduction of anions to its complete termination. In the case of the BrO4- anion, during the reduction of which the near-electrode layer experi ences alkalization, at some pH values, the effect is discovered of noncoinc idence of regions of potentials of adsorption and inhibition of the process which disappears in relatively acidic (pH approximate to 4.0) and buffer s olutions. The effects discovered are explained from the viewpoint of a part icipation of 1-AdCOOH in acidic-basic equilibriums both in the bulk solutio n and in the near-electrode layer. Estimates are conducted of pH and concen tration of 1-AdCOOH in the near-electrode layer.