The cover image shows how the reaction path of the Cl2 evolution reaction (CER) is investigated by combining electrochemical and spectroscopic methods, as reported by Schuhmann et al. on page 1897. Oxidation and reconstruction of the catalyst surface during CER is a consequence of the interaction between RuO2 and water. The solvent is crucial in the formation of an oxygen-containing hydrophilic layer, which is a key prerequisite for electrocatalytic Cl2 formation. New insights in the general understanding of electrocatalysis are obtained utilizing the vibration frequencies of the crystal lattice as a dynamic catalytic descriptor, instead of thermodynamic descriptors such as the adsorption energy of intermediates. Interpretation of the derived “volcano”-curve suggests that electrocatalysis is governed by a resonance phenomenon.