Atomic Sn₁–Ir pair-modified dilute alloy clusters for efficient hydrogen oxidation electrocatalysis

Modifying Ir by foreign metals with oxophilicity is a promising strategy to accelerate the hydrogen oxidation kinetics. However, uncontrolled enrichment and oxidative dissolution of metastable oxophilic dopants in conventional Ir-based alloys impair their activity and durability. Here, we address these challenges by atomically dispersing oxophilic Sn sites within Ir clusters to form dilute alloys. The Sn₁–Ir pairs, confined within an atomic-scale lattice, prevent excessive *OH coverage caused by oxophilic site enrichment, while also reducing durability loss due to the dissolution of metastable dopants. Our analysis reveals that the Sn₁–Ir pairs facilitate electron transfer between Sn₁ and adjacent Ir sites, generating electron-rich Ir atoms and electron-poor Sn atoms. This modulation weakens *H and CO adsorption on Ir sites while enhancing OH adsorption on Sn sites. The resulting catalyst shows improved catalytic hydrogen oxidation performance in alkaline media, with mass activities 6.4 and 10.7 times higher than that of Ir/C and Pt/C, respectively. Under CO poisoning conditions, it retains 90.9% of its initial activity, outperforming both Ir/C and Pt/C. This work offers new perspectives on the design of dual-site catalysts for hydrogen oxidation catalysis.