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The development of affordable, low-iridium-loading, scalable, active, and stable catalysts for the oxygen-evolution reaction (OER) is a requirement for the commercialization of proton-exchange membrane water electrolyzers (PEMWEs). However, the synthesis of high-performance OER catalysts with minimal use of the rare and expensive element Ir is very challenging and requires the identification of electrically conductive and stable high-surface-area support materials. We developed a synthesis procedure for the production of large quantities of a nanocomposite powder containing titanium oxynitride (TiON x ) and Ir. The catalysts were synthesized with an anodic oxidation process followed by detachment, milling, thermal treatment, and the deposition of Ir nanoparticles. The anodization time was varied to grow three different types of nanotubular structures exhibiting different lengths and wall thicknesses and thus a variety of properties. A comparison of milled samples with different degrees of nanotubular clustering and morphology retention, but with identical chemical compositions and Ir nanoparticle size distributions and dispersions, revealed that the nanotubular support morphology is the determining factor governing the catalyst's OER activity and stability. Our study is supported by various state-of-the-art materials' characterization techniques, like X-ray photoelectron spectroscopy, scanning and transmission electron microscopies, Xray powder diffraction and absorption spectroscopy, and electrochemical cyclic voltammetry. Anodic oxidation proved to be a very suitable way to produce high-surface-area powder-type catalysts as the produced material greatly outperformed the IrO 2 benchmarks as well as the Ir-supported samples on morphologically different TiON x from previous studies. The highest activity was achieved for the sample prepared with 3 h of anodization, which had the most appropriate morphology for the effective removal of oxygen bubbles.

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Vanadium oxide (V 2 O 5 ) films were prepared by dip-coating from V-oxoisopropoxide sols and heating at 300ЊC for 1 h. Transmission electron microscopy combined with small area electron and X-ray diffraction revealed that the films consist of disordered V 2 O 5 grains with an orthorombic structure (P mmn ). Electromotor force (emf), cyclic voltammetric (CV), and chronocoulometric measurements, combined with in situ ultraviolet-visible (UV-vis) spectroelectrochemical measurements, revealed similar electrochromic and electrochemical properties with other sputtered and sol-gel derived V 2 O 5 films. IR absorbance and reflectionabsorption spectra, performed at near-grazing incidence angle (NGIA) conditions (80Њ, P-polarized), allowed us to compare the observed transverse optical (TO) and longitudinal optical (LO) frequencies of films with the TO and LO mode frequencies obtained from the dispersion analyses of V 2 O 5 crystalline reflection IR spectra. TO and LO spectra of charged films show that Li ϩ ...O interactions modify the terminal V-O A (vanadyl), bridging V-O B -V, and edge-sharing V-O C stretching frequencies, suggesting that these interactions take place between the oxygens bordering the cavities in which Li ϩ ions are accommodated during charging. The red-frequency shift of the V-O A stretchings [1016 cm Ϫ1 (TO), 1035 cm Ϫ1 (LO)] and the disappearance of the bridging V-O B -V stretching mode [795 cm Ϫ1 (TO), 895 cm Ϫ1 (LO)] can be used as a diagnostic tool to differentiate between films cycled in the safe and unsafe potential regions. A polaron absorption was observed above 2000 cm Ϫ1 in the ex situ TO and in situ NGIA reflectionabsorption (LO) spectra of films charged in the safe potential region.