Advances in Thermodynamic-Kinetic Model for Analyzing the Oxygen Evolution Reaction

A good electrochemical performance for a multistep electron transfer reaction calls for low thermodynamic energy barrier, fast kinetics, and abundance of surface reactive intermediates. While physical and spectral characterizations fail to obtain most of these details because of interference from the electrolyte and dynamic surface structures under reaction conditions, electrochemical measurements instead are able to provide the most direct information. A thermodynamic-kinetic model was developed in our previous work, which showed great capability to extract the adsorption energies of reactive intermediates through the Tafel plot without considering the exact structures of catalysts in the oxygen evolution reaction (OER). In this work, a more adaptive model in combination with probing the methanol oxidation reaction was developed. This approach offers the following advantages: From the aspect of thermodynamics, an experimentally rationalized adsorption profile could be obtained without the requirement to know the scaling factors of reactive intermediates. From the aspect of surface structure, the potential induced change of intermediates’ coverage in the reaction could be described with high sensitivity. From the aspect of kinetics, multiple Tafel slopes in a single Tafel plot could be explained by potential induced variation in intermediates’ coverage and activation energy in the rate-determining step (RDS). A volcano relation between the symmetry factor and adsorption energy was also discerned and discussed, showing the strong correlation between thermodynamics and kinetics. Our model offers a promising analyzing tool by providing essential information on the electrochemical interface and both thermodynamic and kinetic properties of catalysts, which are important for the design of next-generation high-performance catalysts for multistep electrochemical reactions.