Electrochemically Active Surface Area: Voltammetric Charge Correlations for Ruthenium and Iridium Dioxide Electrodes

Electrodes made of ruthenium and iridium oxides on titanium substrates are currently used in many electrochemical processes, in particular the chlor‐alkali industry. Their electrocatalytic activity are attributed to both surface area effects and their intrinsic catalytic nature. In order to compare this intrinsic activity of candidate electrode materials, their electrochemically active surface area (EASA) must be determined. In this paper, EASA‐voltammetric charge correlations are presented for and electrodes, using zinc ion adsorption for measuring the EASA. The correlation for on titanium (1.5–14 mg/cm 2 ) was found to be 2643 cm 2 /C (0.05–1.0V vs. SCE). In the case of on titanium (0.88–2.7 mg/cm 2 ), it was observed to be 3626 cm 2 /C. Kinetic measurements of a simple redox couple were consistent with the EASA correlation for surfaces. However, in the case of , the use of EASA correlation gave kinetic rate constants one order below the expected magnitude. A dimensionless group comparison based on porous electrode accessibility indicates that the and behave in a similar manner, eliminating this reason for the variation in rate constants.