Atomic Contact With Cu Single Atom Promoting Pt3 Clusters for High-Performance Acetylene Semihydrogenation.

Understanding how second metal species modulate catalytic performance remains a central challenge in bimetallic heterogeneous catalysis. Here, we report a controllable strategy to construct atomically contacted and spatially isolated structures between Pt3 clusters and Cu atoms on γ-Al2O3 by atomic layer deposition (ALD), enabling direct interrogation of metal-metal synergy. By regulating anchoring sites around Pt clusters, Cu atoms can be selectively positioned either by bonding to Pt to form Pt3Cu1 clusters or by separating into isolated Cu single atoms. Comprehensive characterizations and theoretical calculations reveal that Cu single atom can act as an effective promoter only when directly bonded to Pt3 clusters. As electron donator, the bonded Cu atom can enhance the hydrogen dissociation ability of Pt clusters, weaken their strong acetylene adsorption, and facilitate ethylene desorption, thereby overcoming the activity-selectivity trade-off in selective hydrogenation of trace acetylene. In contrast, isolated Cu single atom fails to promote Pt3 clusters and even deteriorate selectivity. These results demonstrate that Pt─Cu bond formation, rather than simple proximity, governs synergistic effects in bimetallic cluster catalysts. This work establishes a clear design principle for atomically engineered catalysts and offers a general strategy to independently optimize catalytic activity and selectivity.