Cover Picture: Role of Water in the Chlorine Evolution Reaction at RuO₂-Based Electrodes—Understanding Electrocatalysis as a Resonance Phenomenon (ChemSusChem 10/2012)

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.