In situ observation of the potential-dependent chemical state and structure of a Cu monolayer deposited on the surface of carbon-supported platinum clusters

A complete electrochemical oxidation-reduction cycle for a Cu monolayer on carbon-supported Pt clusters in alkaline solution has been monitored in sit u by X-ray absorption spectroscopy. No desorption of Cu was observed upon o xidation. Near-range order and oxidation state of the Cu layer as a functio n of potential was obtained by in situ X-ray absorption spectroscopy. In co ntrast to bulk copper, the adsorbed copper monolayer transforms directly fr om the reduced state to Cu2+ and from the oxidized form to Cu-0. Adsorption of OH- ions on the Cu layer was observed for potentials below those for th e Cu-0 --> Cu2+ and Cu2+ --> Cu-0 transitions.