The catalyst that stores charge first Alkaline oxygen evolution on Co3O4 involves more than adsorption and electron transfer at a fixed surface. The article draws on operando electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D), surface X-ray diffraction (SXRD), Raman, UV/Vis and impedance spectroscopy. On this basis, it discusses pseudocapacitive oxidation of cobalt ion sites, electrolyte uptake and near-surface transformation, and asks which of these changes are kinetically coupled to electrocatalysis. 4 81-84 81-84 Deutsche Bunsen-Gesellschaft für physikalische Chemie e.V.