Metal nanoparticle (NP) catalysts are widely used in catalytic reactions. The size of the particles greatly affects their performance, especially the activity and selectivity. The tight coupling between the geometric and electronic effects related to the particle size tends to restrict the optimization of the catalyst’s performance, and, in many catalytic reactions, it results in a see-saw relationship between activity and selectivity. Therefore, it remains a challenge to design and synthesize a catalyst that simultaneously achieves high selectivity and high activity.  

In a study published in Nature Catalysis, Prof. LU Junling and Prof. LI Weixue from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences, by focusing on the selective hydrogenation reaction of halonitrobenzenes (HNBs), designed and synthesized a core–shell bimetallic Au@Pt/SiO₂ catalyst with a monolayer platinum shell (Au@1ML-Pt), which solves the see-saw dilemma. 

The researchers first found that Pt/SiO₂-catalyzed hydrogenation of HNBs into haloanilines (HANs) showed a see-saw relationship in its activity and selectivity. Then they pointed out that the lattice-stretch and the shift of the 5d-band center of Pt, caused by placing a monolayer of Pt(111) on the surface of Au(111), was capable of raising the catalyst’s activity and sustaining a high selectivity. Based on the theoretical predictions, they fabricated the Au@Pt/SiO₂ catalyst with Au@1ML-Pt using the technique of atomic layer deposition (ALD). They found that the geometric and electronic structure of Pt was well-modulated in the bimetallic catalyst.  

The Au@1ML-Pt catalyst has good performance in catalyzing the hydrogenation of HNBs. It showed an over 99% selectivity and a relatively high activity, resulting in a far better yield of HANs in the product than that of Au-Pt alloy or monometallic Pt catalyst. 

The model of a core–shell bimetallic catalyst with a monolayer metallic shell holds unique characteristics in its geometric and electronic structures. It provides a promising strategy for designing metallic catalysts with high activity and high selectivity in the future.