Kinetics and mechanism of the cerium(IV)/cerium(III) redox reaction on a platinum electrode

The oxidation and reduction kinetics of the CeIV/CeIII redox reaction at a Pt electrode in sulphuric acid are reported. In contrast to previously reported studies, the thickness of platinum oxide on the electrode surface was standardised. Current efficiency data, voltammograms and Allen–Hickling plots are presented, and the reaction order in [H+], [SO2–4] and [CeIII], [CeIV] is examined. Evidence is presented to suggest that the mechanism is not the simple: Ce4++ e–→ Ce3+ which has hitherto been assumed, but rather that complex intermediate species, most probably sulphato complexes, are involved.