Influence of sulphuric acid concentration on current yield of peroxodisulphate

Abstract

Overall anodic polarization curves and partial polarization curves of oxygen evolution and formation of peroxosulphates (S2O82- + SO52-) were measured potentiostatically on a smooth platinum anode in 1-13M-H2SO4 at 25 °C at a small degree of conversion of SO42- to S2O82- ions. The known dependences of the current yield of peroxodisulphate on the total concentration of sulphuric acid at various current densities were substantiated. The found results were used to explain mechanism of formation of S2O82- ions, according to which in contrast to previous explanations the possibility of simultaneous discharging of SO42- and HSO4- ions is considered with partial rates depending on the reaction conditions. A mathematical formulation of this mechanism is in qualitative agreement with experiments, an evidence for the probability of the mechanism. A correlation of the current yield with the actual concentrations of SO42- and HSO4- ions at various temperatures helps to further elucidate the negative influence of the temperature on the current yield.