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 appliedtechniquefor investigating the kinetics of these reactions limited by poormass transfer, e.g., for reactions involving gaseous reactants oflow concentration as a result of limited solubility. For irreversiblereactions of apparent first-order kinetics, kinetic parameters suchas the kinetic current and the rate constant are usually derived basedon the Koutecky-Levich equation. In this Perspective, we willdiscuss several frequently encountered and important issues that maysignificantly reduce the accuracy of the kinetic analysis. We willfocus on (i) variation or improper identification of the diffusionlimiting current; (ii) deviation of the RDE system from the steady-stateconditions; (iii) effect of catalyst loading; (iv) reactions withreactants of reaction order deviating from one; and (v) the mass transportlimiting of more than one reactant. Possible origins of the errorthat affects the accuracy of the kinetic analysis will be discussed,and practical protocols to avoid such errors will be recommended.