Facilitating room-temperature oxygen ion migration via Co-O bond activation in cobaltite films
Oxygen ion migration in strongly correlated oxides can elicit dramatic changes in crystal structure, chemical and magnetoelectric properties, which holds promising for wide applications in catalysis, energy conversion, and electronics. However, the high strength and stability of metal-oxygen (M-O) bonds cause large thermodynamic barrier of oxygen migration. Here, we design the Co-O bond activation in cobaltite (SrCoOx) films by Au-nanodot-decoration. Charge transfer from Au to SrCoOx effectively weakens Co-O bond, meanwhile Co-O-Au synergistic bonding remarkably decreases the migration barrier of oxygen ions. Fast oxygen evolution occurs at the perimeter of Au/SrCoOx interface, and the chemical potential gradient of O2− drives inner ion diffusion to surface. Consequently, bias-free topotactic phase reduction from perovskite SrCoO3–δ to brownmillerite SrCoO2.5 has been achieved at room temperature. Our finding explores a new dimension to accelerate oxygen ion kinetics in transition-metal oxides from the aspect of interfacial bond activation, which is significant for developing oxide/noble-metal interfaces for high-efficiency ion migration and redox catalysis at low temperature.