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Abstract

Simplified IrO_x
electrodes lacking typical mud crack structure have been produced on polycrystalline Ti cylinders with spin-coating using an iridium acetate solution and are compared to thicker samples in terms of stability, composition, and suitability as a model system. The spin-coating process forms smooth, thin islands of IrO_x
with limited cracking and decreases the surface-to-bulk ratio to allow a more intimate study of the growth, composition, and stability of the layer without the complications of the mud crack morphology. XPS and XRD measurements show a resulting (Ir,Ti)O_x
surface (x near 2) with OH– groups and H₂O. Cyclic voltammetry measurements indicate the expected high catalytic activity for the oxygen evolution reaction as well as a dry IrO_x
phase resulting from the thermal manufacturing process, although evidence of hydrous phases are found in XPS. Both films required only small overpotentials for the oxygen evolution reaction, with the spin-coated sample showing a slightly lower activity. CO temperature desorption spectroscopy analysis showed CO → CO₂ oxidation and, in combination with XPS, an unstable surface. The oxidation of CO was not due to the TiO_x
, and the absence of any evidence of an Ir-suboxide phase indicates the presence of near-surface active species present after synthesis or an active surface termination.