Reversibility of platinum voltammograms in aqueous electrolytes, ionic product and dissociative adsorption of water

Abstract

Well-known reversibility of platinum voltammograms in supporting aqueous electrolytes formally contradicts the equilibrium defined by the ionic product of water: K w = [H +] · [OH −] ≅ 1 × 10 14, since at any pH value, concentration of one of these ions should be too low (⩽10 7 M) to ensure reversibility in the whole potential region at usual scan rates. This contradiction could be overcome by allowing dissociative water adsorption on platinum. All available relevant data obtained by in situ physical methods appear to provide indirect experimental evidences for this hypothesis.