Titanium deposition onto Cu₂O/Pt(111) films: violent redox-chemistry at a metal-oxide interface

Abstract Metal-oxide interactions are pivotal for the functionality of supported-metal catalysts. In this work, x-ray photoelectron spectroscopy and scanning tunneling microscopy (STM) are employed to study the interface reaction between Ti metal and crystalline Cu 2 O/Pt(111) films. Already at room-temperature, deposited Ti spontaneously oxidizes to predominately +4 and +2 charge states at low and high coverage, respectively. The electron transfer is accompanied by oxygen migration towards the Ti ad-layer, whereby Cu 2 O gradually reduces to Cu and Ti converts to TiO 2 . The process gets reinforced by heating the system to 450 K. The local nature of the interface reaction is derived from STM conductance spectroscopy. At low Ti load, electron transfer out of the ad-layer leads to a downward bending of the Cu 2 O electronic bands. With increasing coverage, the band bending ceases and formation of a Cu x O/TiO x hetero-junction is revealed in the spectra. The signature of metallic ad-particles is only detected at high Ti load, when electron tunneling into Ti deposits bound to the oxide spacer leads to Coulomb-charging effects. The observed strength of the redox reaction at the Ti/Cu 2 O interface impressively demonstrates the high reductive power of titanium.