Total Galvanic Replacement Strategy for Synthesizing Hollow Multimetallic Nanocrystals Toward Enhanced Catalysis

Abstract The synergistic effects in multimetallic nanocrystals make them attractive catalysts, but constructing hollow architectures with controlled features poses substantial challenges. Here, the galvanic replacement reaction between Ag nanocubes and three metal precursors (Pd 2+ , Pt 2+ , and Au 3+ ) is used to demonstrate that both atomic mixing and atomic arrangements of the resulting AgPdPtAu hollow nanocrystals can be tuned through four distinct precursor addition strategies. This study reveals that increasing the mixing entropy induces a transition from phase‐separated domains to a homogeneous solid solution. Moreover, preferential bonding between deposited and template metals promotes the formation of nanocubes enclosed by {100} facets with square atomic arrangements. When dispersed on semiconductor supports, these facet‐controlled AgPdPtAu hollow nanocrystals exhibit enhanced photocatalytic hydrogen production. Operando synchrotron X‐ray photoelectron spectroscopy and density functional theory calculations reveal that Pt‐containing bridge sites act as primary hydrogen adsorption centers, exhibiting high local electron density and strong hydrogen binding. Additionally, bridge sites formed by mixed‐affinity metal pairs (e.g., AuPt and AgPd), coupling strongly (Pt or Pd), and weakly (Au or Ag) hydrogen‐adsorbing elements, exhibit near‐optimal hydrogen adsorption and serve as key active sites for hydrogen evolution. This study establishes a versatile approach for engineering multimetallic hollow nanocrystals with tunable structures for catalytic applications.