The turnover frequency (TOF) is conventionally used to measure activity in catalysis but is rarely used in electro-catalysis, which uses the value of the interfacial current instead. Herein, a procedure to quantify the TOF for the ethanol oxidation reaction (EOR) in electro-catalysis is proposed and compared with the value observed in catalysis (Sapi et al., Nano Lett., 14 (2014) 6727). The intrinsic TOF in an alkaline medium is 9.23 molecules site−1·s−1, which is three times larger than the value obtained in an acidic medium, explaining the major differences observed between the interfacial currents recorded during cyclic voltammetry and chronoamperometry in the two media. In the future this methodology will be extended to single crystal surfaces and nanoparticles, assisting the development of electro-catalysts on a more fundamental theoretical basis.