ELECTROCATALYTIC ACTIVITY OF ANODES IN REFERENCE TO CR(III) OXIDATION REACTION

The catalytic activity of the anodes used for the oxidation reaction of Cr(III) ions is studied. In the case of the MnO2 electrode it is shown that the electro-oxidation of Cr(III) proceeds involving the oxygen-containing particles chemisorbed on the anode. The first reaction step is the anodic ionization of water resulting in the formation of OH-groups chemisorbed on the electrode surface which interact with the Cr(III) compounds in the following chemical step. The adsorbed complex formed in this case is oxidized to Cr(VI) compounds In the following electrochemical step. It is assumed that there is a correlation between the reaction rate of the Cr(III) electro-oxidation and the adhesion strength between the electrode surface and chemisorbed oxygen. The series of increasing electrocatalytic activities correlates almost completely with that of the decreasing adhesion strengths between the oxygen-containing particles and the electrode surface.