Extraordinary Stability of IrO2(110) Ultrathin Films Supported on TiO2(110) under Cathodic Polarization

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Down to a cathodic potentials of -1.20 V versus the reversible hydrogen electrode, the structure of IrO2(110) electrodes supported by TiO2(110) is found to be stable by in situ synchrotron-based X-ray diffraction. Such high cathodic potentials should lead to reduction to metallic Ir (Pourbaix diagram). From the IrO2 lattice parameters, determined during cathodic polarization in a H2SO4 electrolyte solution (pH 0.4), it is estimated that the unit cell volume increases by 1% due likely to proton incorporation, which is supported by the lack of significant swelling of the IrO2(110) film derived from X-ray reflectivity experiments. Ex situ X-ray photoelectron spectroscopy suggests that protons are incorporated into the IrO2(110) lattice below -1.0 V, although Ir remains exclusively in the IV+ oxidation state down to -1.20 V. Obviously, further hydrogenation of the lattice oxygen of IrO2(110) toward water is suppressed for kinetic reasons and hints at a rate-determining chemical step that cannot be controlled by the electrode potential.


  • Tim Weber
  • Vedran Vonk
  • Marcel J.S. Abb
  • Jonas Evertsson
  • Martina Sandroni
  • Jakub Drnec
  • Andreas Stierle
  • Edvin Lundgren
  • Herbert Over
Enheter & grupper
Externa organisationer
  • Justus Liebig University Giessen
  • German Electron Synchrotron (DESY)
  • European Synchrotron Radiation Facility
  • University of Hamburg

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Fysikalisk kemi
Sidor (från-till)9057-9062
Antal sidor6
TidskriftJournal of Physical Chemistry Letters
StatusPublished - 2020
Peer review utfördJa