Anodic Processes at Smooth Platinum Electrode in Concentrated Solution of Methanesulfonic Acid

Abstract

Some features of processes occurring during the polarization of smooth platinum electrode in 10.0 M methanesulfonic acid (CH₃SO₃H) solution at high anodic potentials are studied by the cyclic voltammetry method. On cyclic voltammograms of smooth platinum electrode in concentrated methanesulfonic acid solution, well-pronounced oxidation waves are observed at potentials E = 2.0–2.5 V and E = 2.9–3.7 V. The electrochemical processes occurring in 10 M CH₃SO₃H solution within the E = 2.0–2.5 V potential range are shown to be associated with discharge of water molecules; the broad oxidation wave within the potential range of E = 2.9–3.7 V is related to the formation of peroxide compounds. Based on the electrochemical measurements and analysis of products of preparative electrooxidative electrolysis, the formation of a complex organosulfur peroxide compound, bis(methanesulfonyl) peroxide CH₃S(O)₂OOS(O)₂CH₃ (other names: dimethyl disulfoperoxide, or dimethanesulfonyl peroxide, or dimesylate peroxide) is established. Anodic oxidation mechanism in concentrated CH₃SO₃H solutions is proposed. It is supposed that the formation of the peroxide compound is associated with the participation of mesylate-radicals that dimerize at the smooth platinum anode and then are desorbed into the solution bulk.