Insight into the role of Cd atoms in clusters for the oxidation reaction of styrene

Abstract

The precise construction of catalytic sites on the surface of metal nanoclusters is of great significance, but it currently faces substantial challenges. In this work, we precisely dope Cd atoms on cluster surfaces to synthesize the structurally well-defined Au16Cd2(2-SAdm)16 (abbreviated as Au16Cd2) cluster via the metal exchange strategy. Furthermore, using single-crystal X-ray diffraction to determine the geometric structure of Au16Cd2. Structural analysis reveals that the Au16Cd2 cluster features an Au6Cd2 bi-tetrahedral core, which resembles the core of the reported Au24 cluster. The two Cd atoms occupy two vertex sites of the kernel and exhibit significantly stronger Hirshfeld charges than the Au atoms, which may lead to distinct catalytic behaviours. Using styrene oxidation as a model reaction, Au16Cd2 demonstrates substantially higher conversion than Au24 (98% vs. 34%). Combining Density functional theory (DFT) calculations and experimental results to explore the reason for this difference, the results show that the Cd sites facilitate electron withdrawal from the C=C bond of styrene to oxidation. To further validate the critical role of Cd atoms in catalyzing styrene oxidation, we extended the study to a broader range of clusters. The results consistently showed that AuCd alloy clusters exhibit superior catalytic performance compared to gold clusters.