Developing efficient and durable bifunctional catalysts is essential for advancing hydrogen production and energy storage technologies, including Proton Exchange Membrane Water Electrolyzers (PEMWE) and Unitized Regenerative Fuel Cells (URFCs). Thus, iridium-based catalysts focusing on iridium-decorated platinum nanoparticles for URFCs and titanium-supported iridium nanoparticles for PEMWEs have been investigated.

Iridium-decorated platinum nanoparticles with several Ir-to-Pt ratios (Ir10/Pt90, Ir20/Pt80, and Ir40/Pt60) were studied to determine the catalyst composition that optimizes the performance  or oxygen reduction (ORR) and evolution reactions (OER). Among these, Ir40/Pt60 exhibited the highest OER mass activity (571.4 mA mgIr⁻¹), while Ir20/Pt80 demonstrated enhanced  multifunctional efficiency (57.7%), making it the most promising URFC catalyst.

For PEMWEs, iridium nanoparticles supported on TiO2, TiC, and TiN were evaluated. Ir/TiO2 and Ir/TiC achieved improved OER activity, with overpotentials of 260 mV and 259 mV at 10 mA cm^-2, respectively, comparable to unsupported Ir black (253 mV). In-operando and post-mortem analyses revealed degradation pathways specific to each support catalyst, such as oxidation, dissolution, or structural changes.

This work highlights the relationship between catalyst composition, morphology, and support properties with the catalyst activity, providing a foundation for designing advanced materials for sustainable energy applications.

Keywords: iridium, platinum, nanoparticles, electrocatalysts, titanium-based supports, unitized regenerative fuel cells, water electrolyzer.

corresponding author: e-mail: lublare93@gmail.com