In situ atomic-scale imaging of the metal/oxide interfacial transformation

Directly probing structure dynamics at metal/oxide interfaces has been a major challenge due to their buried nature. Using environmental transmission electron microscopy, here we report observations of the in-place formation of Cu₂O/Cu interfaces via the oxidation of Cu, and subsequently probe the atomic mechanisms by which interfacial transformation and grain rotation occur at the interfaces during reduction in an H₂ gas environment. The Cu₂O→Cu transformation is observed to occur initially along the Cu₂O/Cu interface in a layer-by-layer manner. The accumulation of oxygen vacancies at the Cu₂O/Cu interface drives the collapse of the Cu₂O lattice near the interface region, which results in a tilted Cu₂O/Cu interface with concomitant Cu₂O island rotation. These results provide unprecedented microscopic detail regarding the redox reactions of supported oxides, which differs fundamentally from the reduction of bulk or isolated oxides that requires the formation of new interfaces between the parent oxide and the reduced phase.Metal/oxide interfaces play an important role in heterogeneous catalysis and redox reactions, but their buried nature makes them difficult to study. Here, the authors use environmental transmission electron microscopy to probe the atomic-level transformations at Cu₂O/Cu interfaces as they undergo redox reactions.