Understanding less-noble-metal (M) dissolution of Pt-alloy-based oxygen reduction reaction (ORR) electrocatalysts as well their interaction with Pt surface is crucial for maximizing their performance. In pursuing this goal, two ORR electrocatalysts – a benchmark Pt-Co/C and an in-house designed Pt-Cu/C materials are investigated. Both are characterized with a range of standard techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with energy dispersive spectroscopy (EDX) and thin film-rotating disc electrode (TF-RDE) measurements. A special focus is put on combining the latter with a highly sensitive electrochemical flow cell (EFC) on-line connected to inductively coupled plasma mass spectrometry (ICP-MS) measurements. A combination of standard and novel techniques provides unprecedented insights into the dissolution behavior and dynamics of metals as well as their subsequent surface interactions and effects on the electrochemical performance. A special focus is devoted to the significance of electrocatalyst activation protocols and their effects on metal dissolution. Distinct differences in the behavior of Pt-Cu and Pt-Co alloys are revealed which will help develop proper protocols for practical implementation of Pt-alloy electrocatalysts.

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, X-ray 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 IrO₂ 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.