LAUSR

Electron transfer is the most crucial step in several electrochemical reactions; therefore, finding alternative ways for its control represents a huge step toward the design of advanced electrocatalytic materials. We demonstrate that the electrons from an oxide-buried metal interface can be efficiently exploited in electrochemical reactions. This is proven by studying the electrochemical activity of model systems constituted by cobalt oxide ultrathin (<2 nm) films epitaxially grown on Pd(100). Metal/metal oxide interfacial hybridization and electron tunnelling from the metal substrate through the oxide endow CoOx ultrathin films with exceptional electrochemical activity and improved poison tolerance. In situ XPS and Raman measurements indicate that during the oxygen reduction reaction, CoO is transformed into CoOOH, whereas Co3O4 is stable. These results demonstrate that the in situ study of ultrathin films on single crystals is a powerful method for the identification of materials active phase and of nov...