Atmosphere‐Dependent Encapsulation and Dewetting in Au/ZnO: A Transient‐Overlayer Strategy for Maximizing Metal‐Support Interfacial Catalysis

ABSTRACT The strong metal–support interaction (SMSI) has traditionally been viewed as a static phenomenon that modulates catalysis through site blocking. Here, we challenge this classical view by demonstrating that SMSI in Au/ZnO is an atmosphere‐dependent dynamic process that can be harnessed to engineer catalytic interfaces. Using in situ transmission electron microscopy, infrared spectroscopy, and X‐ray photoelectron spectroscopy, we track the structural evolution of the Au/ZnO interface throughout redox cycles and reaction conditions. Under H 2 , oxygen vacancy formation triggers ZnO x encapsulation, followed by AuZn alloying at elevated temperature, which induces nanoparticle reconstruction and expands the metal‐support interfacial area. Upon exposure to O 2 , the alloy decomposes, and the ZnO x overlayer dewets into nanoislands, with some regions undergoing complete retraction. Under CO oxidation conditions, the fully encapsulated state is lost, yet the H 2 ‐pretreated catalyst exhibits superior activity and stability. This enhancement arises from alloying‐induced interface reconstruction together with residual ZnO nanoislands that persist after dewetting, creating an enlarged and highly active metal–oxide interface. Our work demonstrates a transient‐overlayer strategy for catalyst design, in which a pre‐formed SMSI layer serves as a precursor that, through controlled redox cycling or reaction conditions, transforms into a high‐interface area, sintering‐resistant catalytic architecture, thereby transcending the classical encapsulation‐activity dilemma.