Controlling the Thermally Induced Metal–Support Interaction and Ligand Effect of ATO-Supported IrO _<i>x</i> Electrocatalysts for the Oxygen Evolution Reaction

Antimony-doped tin oxide (ATO) serves as a promising corrosion-resistant and conductive support for reducing iridium (Ir) loading in oxygen evolution reaction (OER) catalysts for proton-exchange membrane electrolysis. While metal–support interactions (MSIs) are well-known to modify the catalyst activity and stability in heterogeneous thermal catalysis, their role in electrocatalysis─particularly for the ATO-supported Ir-based OER catalysts─remains underexplored. Herein, we disclose a thermally induced MSI during the synthesis of ATO-supported IrO x catalysts, which decisively controls the OER activity and stability. Upon air annealing of the ATO-supported Ir chloride precursor, Ir nanoparticles initially formed at 300 °C, transforming into an epitaxial rutile phase IrO x surface layer partially covered by ATO at 400 °C and finally evolving into an Ir–Sn mixed rutile oxides surface at 600 °C, demonstrating a strong MSI under high temperatures. This further leads to declined OER activity with increasing temperature, highlighting the importance of temperature control during the catalyst annealing. We further demonstrate that residual chlorine from the precursors markedly suppresses OER performance. Annealing under H 2 removes chlorine but weakens the MSI and induces nanoparticle agglomeration, compromising the catalytic stability. In contrast, using nitrate precursors under low-temperature air annealing effectively eliminates chlorine while preserving high IrO x dispersion, yielding simultaneous gains in both activity and durability. These results provide critical guidance for rational synthesis of ATO-supported Ir-based electrocatalysts with a finely tuned MSI through a controlled annealing atmosphere and precursor chemistry.