Cathodic behaviour of IrO2 electrodes in alkaline solution Part I: Electrochemical surface characterization

Abstract

IrO2 electrodes prepared by thermal decomposition of IrCl3 on a titanium support at temperatures of calcination between 300 and 500°C have been characterized by cyclic voltammetry and potential steps. ‘Standard’ voltammetric curves have been recorded between −0.65 and 0.35 V vs SCE (prior to H2 and O2 evolution) as a ‘fingerprint’ of the surface state, and the associated charge,q *, has been used to monitor the morphology of the active layer. The effect of hydrogen evolution has been investigated by progressively decreasing the negative potential limit, and by increasingly holding the electrode under hydrogen evolution at a constant potential. Phenomena of proton penetration beneath the ‘outer’ surface into an ‘inner’ surface have been quantified by potential step experiments. The effect of storing the electrodes in water rather than in the open air has also been investigated. The thermal oxides lose their typical features at calcination temperature < 350° C. Cathodic load does not appear to cause macroscopic modifications of the surface state.