An evaluation of the size-dependent electrocatalytic activity of single IrO ₂ nanoparticles <i>via</i> nano-impact electrochemistry

Characterizing the intrinsic electrocatalytic activity of single nanoparticles (NPs) is challenging due to the need for additives and binders in conventional methods. Herein, we employ the nanoparticle impact electrochemistry (NIE) method to overcome this limitation, enabling the real-time detection of enhanced oxygen evolution reaction (OER) activity at the single-particle level. The current-time curves from the IrO₂ NP impact study consist of repeated current spikes that return to the background level as oxygen forms and covers the NP surface. Leveraging high mass transport, we observed size-dependent electrocatalytic activity, confirming that the intrinsic OER performance scales with NP size. Notably, smaller IrO₂ NPs (7.4 nm) exhibited a tenfold higher turnover number (TON) per unit area compared to larger NPs (23 nm), highlighting the critical role of size control in electrocatalysis. This work offers a reliable approach for structure-activity correlation, which is important in fundamental research, energy-related fields, and biosensing.