Importance of entropic contribution to electrochemical water oxidation catalysis

Electrochemical water oxidation is considered as one of the most important reactions for a sustainable future. However, in heterogeneous water oxidation, atomistic understanding of this four-electron reaction is still elusive. In particular, the mechanism of O-O bond formation, the coupled transfer of proton and electron, and the hopping of high-valent metal-oxo intermediates are challenging issues. To date, binding energy related descriptors have been used successfully to predict the catalytic activities by matching the experimental data and quantitatively comparing the performances. In this Perspective, we attempt to emphasize the significance of entropic contribution, like enthalpy, by highlighting recent literature and calculating the entropy from the available data. We envision that this Perspective can suggest a new research direction toward the catalyst design to control the entropy during water oxidation and be technologically useful for characterizing the temperature effects.