Laser-Induced Nanoscale Engineering of Iridium-Based Nanoparticles for High-Performance Oxygen Evolution

While ruthenium oxide exhibits higher activity, it suffers from significantly lower stability in the acidic oxygen evolution reaction (OER). In contrast, crystalline iridium oxide is among the few materials that remain stable under such harsh conditions. However, its low activity and iridium scarcity require strategies to enhance atomic utilization. Conventional high-temperature post-synthetic processing increases the share of rutile-phase iridium oxide while promoting particle growth, reducing catalytic activity due to a diminished surface area. Here, we present a laser-induced nano-oven method using a silicon dioxide matrix as a nanoscale reaction chamber, enabling solid-state nanoparticle synthesis under ambient conditions while preventing agglomeration and allowing precise size control. The synthesized ultra-small crystalline rutile iridium oxide of ∼2 nm achieves a high mass activity of 350 ± 15 A g_Ir ^-1 at 300 mV overpotential, exceeding that of crystalline RuO₂ and reaching the activity benchmark of RuO₂-based catalysts. Analysis using a channel flow cell with on-line inductively coupled plasma mass spectrometry (ICP-MS) confirms that laser-engineered iridium oxide exhibits superior stability to commercial iridium oxide. Operando electron impact MS provided the synthesis mechanistic insights, demonstrating the potential of this strategy for synthesizing ultra-small crystalline metals and metal oxides for various applications.