Unexpected Redox Rectification by an Electrochemically Prepared Iridium Oxide Electrode/Aqueous Acid Interface.

摘要

In highly acidic aqueous solutions, electrochemically prepared iridium oxide films behave as steady-state insulators and transient rectifiers towards the Ru(NH3)6 3+/2+ redox couple. In less acidic solutions the films show only partial transient rectification or else fully reversible transient behavior, together with Koutecky-Levich type steady-state behavior. Experimental studies as a function of Ru(NH3)6 3+ concentration, solution pH, film thickness, voltammetric sweep rate and electrode rotation rate show that these unusual phenomena are related to: (1) transient uptake of Ru(NH3)6 3+ apparentlv in place of H+, during film-based Ir(IV/III) cycling, (2) Donnan exclusion of Ru(NH3)6 3+ from the reduced film under steady-state conditions and/or (3) film-based diffusional Inhibition of Ru(NH3)6 3+ reduction.