ELECTROOXIDATION OF FORMIC-ACID ON THE IRIDIUM ELECTRODE AS A FUNCTION OF PH

The behavior of the Ir electrode in formic acid solutions of different pH values was studied by cyclic voltammetry. The pH range was 1.6-12. Three different pH zones were observed: in the range 1.6-6 the intensity of formic acid oxidation increases with increasing pH; in the range 6-7, the intensity starts to decrease slowly with increasing pH; in the range 7-12, the intensity decreases very sharply with increasing pH, and the intensity is dramatically dependent on the potential sweep limits; at pH 11, all measurable electrocatalytic activity has already disappeared. The dependence of these phenomena on the electrode surface layer properties and the reaction pathway is discussed.