Kinetics of surface reactions on rotating disk electrodes

The diffusive–convective equation under the hydrodynamic conditions of rotating disk electrodes was solved for electrochemical reactions following the Langmuir–Hinshelwood kinetic mechanism, and an expression has been obtained for the current (reaction rate) as a function of the rotation rate, considering adsorption–desorption equilibrium and slow reaction of adsorbed species on the electrode surface. This expression has been applied to the experimental evaluation of electrochemical oxygen transfer to p-methoxyphenol and p-nitrophenol on lead dioxide electrodes. The Langmuir equilibrium constants and kinetic reaction rate constants obtained with the rotating disk electrode compare well with the corresponding values determined from independent adsorption isotherm and electrolysis studies, respectively, demonstrating that the approach presented appropriately describes the kinetic couplings between mass transport, adsorption–desorption equilibrium, and surface reactions, occurring in processes following the Langmuir–Hinshelwood mechanism.