Challenges in Unravelling the Intrinsic Kinetics of Gas Reactions at Rotating Disk Electrodes by Koutecky–Levich Equation

Rotating disk electrode (RDE) system is a widely applied technique for investigating the kinetics of these reactions limited by poor mass transfer, e.g., for reactions involving gaseous reactants of low concentration as a result of limited solubility. For irreversible reactions of apparent first-order kinetics, kinetic parameters such as the kinetic current and the rate constant are usually derived based on the Koutecky–Levich equation. In this Perspective, we will discuss several frequently encountered and important issues that may significantly reduce the accuracy of the kinetic analysis. We will focus on (i) variation or improper identification of the diffusion limiting current; (ii) deviation of the RDE system from the steady-state conditions; (iii) effect of catalyst loading; (iv) reactions with reactants of reaction order deviating from one; and (v) the mass transport limiting of more than one reactant. Possible origins of the error that affects the accuracy of the kinetic analysis will be discussed, and practical protocols to avoid such errors will be recommended.