Role of Lattice Oxygen in the Oxygen Evolution Reactionon Co 3 O 4 : Isotope Exchange Determined Usinga Small-Volume Differential Electrochemical Mass Spectrometry CellDesign

This work demonstrates the role of lattice oxygen of metal oxide catalysts in the oxygen evolution reaction (OER) as evidenced by isotope labeling together with the differential electrochemical mass spectrometry (DEMS) method. Our recent report assessed this role for Co3O4 using a flow-through DEMS cell, which requires a large volume of electrolyte. Herein, we extend this procedure to different Co3O4 catalyst loadings and particle sizes as well as the mixed Ag + Co3O4 catalyst. We introduce, for the first time, a novel small-volume DEMS cell design capable of using disc electrodes and only <0.5 mL of electrolyte. The reliability of the cell is demonstrated by monitoring gas evolution during OER in real time. This cell shows high sensitivity, high collection efficiency, and very short delay time. DEMS results reveal that only the interfacial part (∼0.2% of the total loading or 25% of surface atoms) of the catalyst is active for OER. Interestingly, the amount of oxygen exchanged on the mixed Ag + Co3O4 cata...