In situ studies of the cathodic stability of single-crystalline IrO2(110) ultrathin films supported on RuO2(110)/Ru(0001) in an acidic environment

Abstract

We investigate with in situ surface X-ray diffraction (SXRD) and X-ray reflectivity (XRR) experiments the cathodic stability of an ultrathin single-crystalline IrO₂(110) film with a regular array of mesoscopic rooflike structures that is supported on a RuO₂(110)/Ru(0001) template. It turns out that the planarity of the single-crystalline IrO₂(110) film is lost in that IrO₂(110) oxide domains delaminate at a cathodic potential of −0.18 V. Obviously, the electrolyte solution is able to reach the RuO₂(110) layer presumably through the surface grain boundaries of the IrO₂(110) layer. Subsequently, the single-crystalline RuO₂(110) structure-directing template is reduced to amorphous hydrous RuO₂, with the consequence that the IrO₂(110) film loses partly its adhesion to the template. From in situ XRR experiments we find that the IrO₂(110) film does not swell upon cathodic polarization down to −0.18 V, while from in situ SXRD experiments, the lattice constants of IrO₂(110) are shown to be not affected. The rooflike mesostructure of the IrO₂(110) flakes remains intact after cathodic polarization to −0.18 V, evidencing that the crystallinity of IrO₂(110) is retained.