Shell-Dependent Hydrogen Spillover Governs the Kinetic Stability of Single-Atom Alloys

High Resolution Image Download MS PowerPoint Slide Single-atom alloy (SAA) catalysts, distinct from conventional catalysts, stabilize isolated dopant atoms through metallic bonding with the host, yet their durability under electrochemical conditions remains insufficiently understood. Here, starting from a systematic thermodynamic screening of 30 Cu(100)-based SAAs, we further interrogate their kinetic stability under reaction conditions, with a particular focus on the role of adsorbed hydrogen (*H), an omnipresent surface species in electrocatalysis. Constant-potential molecular dynamics simulations reveal that *H regulates dopant stability in a coordination-shell-dependent manner. First-shell *H weakens the dopant-Cu interaction, driving Zn and Ag leaching by reducing the migration barriers by 0.73 and 0.48 eV, respectively. In contrast, second-shell *H reinforces dopant-support bonding and suppresses dopant leaching, increasing the Ag leaching barrier from 2.04 to 2.36 eV. This opposite kinetic response originates from shell-specific charge depletion or accumulation at the active site induced by *H, which selectively modulates dopant and its first neighbor Cu (Cu I ) bonding states under applied potential. By contrast, strong dopant-hydrogen interactions immobilize Al and Pd, yielding intrinsically stable catalytic sites even in hydrogen-rich electrochemical environments. Although *H promotes dissolution by weakening metallic bonds and inducing a “pre-activation” lattice expansion state, the actual dissolution process remains constrained by multiple factors, including the interaction between the dopant and *H, as well as the influence of reactants and intermediates in complex electrochemical reactions. These findings establish hydrogen as an active regulator of SAA stability and provide quantitative principles for designing durable SAA electrocatalysts for energy conversion reactions.