Electrochemical Behaviour of Mixtures of V02 and H202 in 1 M HCIO4 on Mercury and Platinized Platinum

Abstract

The electrochemical behaviour of mixtures of VO2 and H2O2 in perchloric acid media was studied both on platinized platinum and on mercury. From voltammetric measurements on platinized platinum it was possible to show that within a definite potential range (from 0.94 to 0.44 V/S.C.E.) the electroreduction of VO(O2)+ to VO2+ and H2O as well as its electro-oxidation to VO2 and O2 arc preceded by the homogeneous decomposition of the VO(O2)^ ion: p VO(O2)+ + H2O->VO1 + H2O2. The rate constant p = 0.74 s-1. The polarographic behaviour of VO(O2)+ at a dropping mercury electrode in the presence of an excess of H2O2 is characterized by the decomposition of this ion according to the preceding equation, followed by the electroreduction of VO2 to VO2 ? and by the subsequent chemical regeneration of VO(O2)+ from VO2+ by hydrogen peroxide. The regeneration reaction was shown to be first-ordcr with respect to VO2 and second-order with respect to H2O2; its rate constant is 1.18 x 1031.2 mol-2. s-1.