Abstract: The influence of Ag⁺ions on the evolution of O₂ and the anodic formation of Mn³⁺at Pt and Pb IPbO₂ anodes was investigated in concentrated sulfuric acid solutions. The ki netic data related respectively to Mn³⁺anodic formation and O₂ anodic evolution at Pt and Pb |PbO₂ anodes in mixed H₂SO₄-MnSO₄ solutions were measured by resolving the steady-state polarization curves. The Tafel slope of steady-state-lgi relationships for Mn³⁺anodic for mation reaction is close to 2×2. 303RT/βF, whereas for O₂ anodic evolution it is close to 2. 303RT/βF(with β 0. 5). The influence of Ag⁺ions on the kinetics of evolution and Mn³⁺anodic formation at Pt and Pb|PbO₂ electrodes was compared as a function of Ag⁺ions concentration. The O₂ evolution and Mn³⁺formation rate increased uniformly with increasing Ag⁺ions concentration in the electrolytes. The kinetic data show that Mn³⁺anodic formation (i(Mn³⁺)) and O₂ anodic evolution (i(O₂)) increased by Ag⁺ions. Since the effect on I (Mn³⁺)was larger than that on i(O₂) at the Pt electrode and smaller than that on i(O₂) at the Pb |PbO₂ electrode, the current efficiency of Mn³⁺formation increased at the Pt electrode and decreased at the Pb |PbO₂ electrode.

Key words: Platinum electrode, Lead dioxide electrode, Anodic formation of Mn³⁺ion, An odic evolution of oxygen, Promoting catalysis of silver(Ⅰ) ion