On the oxygen evolution reaction at IrO2-SnO2 mixed-oxide electrodes

Taking advantage of an innovative sol-gel preparation, Ti-supported coatings based on iridium and tin oxides have been exploited for carrying out a thorough investigation of the oxygen evolution reaction. The research has been performed on devices having an Ir concentration between 20 and 90 mol% of noble-metal, at different temperatures (in the range from 2 to 60 °C) and at four different [H+] concentrations (between 1.0 and 10−3 mol l−1). Approximately constant activation energies have been obtained, with values close to 12.4 kcal mol−1; moreover, the electrode composition proved not to affect the reaction pathway in a significant manner. At all devices, the OER appears to take place with one and the same mechanism, as suggested by the relative constancy of Tafel slopes and reaction orders with respect to H+. The mechanistic path has been confirmed also on the basis of the reaction order with respect to the active site. The effective catalytic activity of the mixed-oxide coating is not influenced by the noble-metal content.