Tracking the Evolution of Iridium Nanocatalysts During Acidic Oxygen Evolution Reaction by Substrate-Stabilized...

Revealing the nanoscale structural evolution of electrocatalysts under realistic acidic oxygen evolution reaction (OER) conditions remains a major challenge. Here, we report the tracking of the evolution of the same individual iridium (Ir) nanocatalysts during prolonged acidic OER by developing identical-location transmission electron microscopy (IL‑TEM). The Ir nanocatalysts dispersed on a TEM grid serving as a working electrode are examined before and after OER operation. We find that the deposition of Au nanoparticles and the formation of SnO₂ nanoclusters occur when a conventional holey carbon-film-supported gold (Au) grid is used at 1.7 V versus the reversible hydrogen electrode (V_RHE), which obscure the identification of genuine Ir reconstruction. By coating the Au grid with Pt to form a stabilized working electrode, these artifacts are effectively suppressed for up to 2.5 h, enabling direct visualization of the nanoscale evolution of Ir nanocatalysts. Control measurements further confirm that the electrochemical response of Ir nanocatalysts on Pt-coated grids is dominated by the Ir catalysts rather than the Pt support. This study demonstrates that IL-TEM provides a practical approach for probing catalyst evolution in harsh, prolonged acidic environments by tracking the same nanocatalysts over extended reaction times, complementing in situ and operando TEM techniques.