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

Tim Weber, Vedran Vonk, Marcel J.S. Abb, Jonas Evertsson, Martina Sandroni, Jakub Drnec, Andreas Stierle, Edvin Lundgren, Herbert Over

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskriftPeer review

5 Citeringar (SciVal)

Sammanfattning

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.

Originalspråkengelska
Sidor (från-till)9057-9062
Antal sidor6
TidskriftJournal of Physical Chemistry Letters
DOI
StatusPublished - 2020

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