IrO2/Ir Composite Nanoparticles (IrO2@Ir) Supported on TiNxOy Coated TiN: Efficient and Robust Oxygen Evolution Reaction Catalyst for Water Electrolysis

It is crucial but challenging to reduce the required noble-metal loading without compromising the catalytic performance of oxygen evolution reaction (OER) catalysts. This study presents a highly active OER catalyst composed of IrO2 with Ir rich surface (IrO2@Ir) nanoparticles supported over nano TiN coated with TiOxNy (IrO2@Ir/TiN). The present approach demonstrates superior OER catalysts with high activity through small, uniformly dispersed IrO2@Ir nanoparticles, along with high durability owing to robust catalyst support and strong catalyst-support interaction. The synthesized IrO2@Ir/TiN with an Ir loading of 40 wt % exhibits a mass-normalized OER activity of 637 Ag-Ir(-1), which is 2.4 times that of the unsupported commercial benchmark IrO2 OER electrocatalyst. The fine nanoparticles and high activity enable significant (similar to 60 %) reduction in the Ir metal loading required to obtain equivalent OER performance. In addition, when evaluated through an accelerated stress test using potential cycling, the catalyst exhibits outstanding durability (79 % retention) compared to that of the commercial equivalent (66 % retention). The OER activity loss was attributed to the catalyst dissolution (30 % loss) and the catalyst particle growth (70 %), with no measurable loss due to the TiN support corrosion. The development of ultra-fine IrO2@Ir nanoparticles and robust ceramic catalyst support significantly improved the Ir utilization and open a new perspective for supported OER catalyst.