Tim Weber Tim Weber Institute of Physical Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany Center for Materials Research, Justus Liebig University, Heinrich-Buff-Ring 16, 35392 Giessen, Germany More by Tim Weber , Vedran Vonk, Marcel J. S. Abb, Jonas Evertsson, Martina Sandroni, Jakub Drnec, Andreas Stierle, Edvin Lundgren, and Herbert Ove
J. Phys. Chem. Lett. 11, 21, 9057–9062 (2020), https://doi.org/10.1021/acs.jpclett.0c02730
Publication year: 2020

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.

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