Isolated Pd ₁ Sites and Surface Hydrogen Cooperativity Enable Selective Direct H ₂ O ₂ Synthesis in PdSn‐Based Catalysts

Direct synthesis of hydrogen peroxide (H 2 O 2 ) from H 2 and O 2 has been pursued as an alternative to the anthraquinone process. Pd‐based catalysts offer high activity by enabling H 2 and O 2 activation, but unselective O─O bond cleavage on Pd limits H 2 O 2 selectivity. Using density functional theory calculations and molecular dynamics (MD) simulations, we show that pristine Pd, Pd 3 Sn, and O/H‐covered Pd 3 Sn surfaces intrinsically favor O─O bond cleavage and fail to account for the high selectivity reported for PdSn catalysts. MD simulations under working conditions show that the PdSn alloy/SnO 2 interface evolves toward atomically dispersed Pd species, with isolated Pd 1 thermodynamically preferred over contiguous Pd 2 and Pd 3 motifs. On Pd 1 /SnO 2 , hydrogen readily dissociates and stabilizes at surface O sites. These surface hydrogens reshape the reaction landscape by tuning the surface electronic structure, thereby promoting O 2 hydrogenation while kinetically suppressing competing O─O bond cleavage. These results reveal cooperative roles of isolated Pd sites and surface hydrogen in governing selectivity and provide mechanistic insight for designing Pd‐based catalysts for H 2 O 2 synthesis.