Abstract text (incl. figure legends and references)
Surface and interface sensitive operando characterization methodologies are required to unlock electrochemical and electrocatalytic processes. Liquid phase electrochemical transmission electron microscopy (TEM) can provide the sensitivity and selectivity at single particle level. Herein, we investigate oxygen-evolving cobalt-based oxides in alkaline solution and we retrieve morphological, structural, chemical information during cyclic voltammetry measurements. We compare the highly active Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) to the spinel Co3O4 and rocksalt CoO. The potential-dependent variation of the local contrast is associated to the modification of the wettability from hydrophobic to hydrophilic character at the oxide surfaces through interfacial capacitance phenomena. Molecular oxygen is probed in real-time during its evolution which results to further dewetting of the surfaces. Our work on catalysts exemplifies the crucial role that surface sensitive and electrochemical microcell TEM techniques can play in detailing the mechanism of electrocatalytic processes and can provide a new characterization framework aiding development of novel design routes for targeted catalyst preparation.