Can One Atom Make A Difference? Enhancement in Aerobic Alcohol Oxidation Catalysis of Au25 Nanoclusters via Single Pd Atom Doping

Alina Bruma

University Of Birmingham

Bimetallic size selected nanoclusters exhibit a tremendous potential in catalysis, with greater opportunities for tailoring the catalytic activity and selectivity than their monometallic counterparts, the key for this catalytic boost residing in the synergy between their constituent elements, in addition to finite size effects [1-3]. A significant effort has been put in the last couple of years to exploit their potential fully, mainly a tight control of nanoclusters chemical composition, ordering, size and shape. However, a high-level control and characterization of small nanoclusters with atomic level precision is still a challenge that has hampered the understanding of the interplay between their structure and reactivity. The present study focuses on a direct, atomic-resolution imaging of calcined Au24Pd1 clusters supported on multiwall carbon nanotubes by employing Aberration-corrected Scanning Transmission Electron Microscopy (Cs-corrected HAADF-STEM). Using gold atoms as mass standards, we confirm the cluster size to be 25 ± 2 atoms, in agreement with the Au24Pd1(SR)18 (SR: thiolate ligands) precursor used in the synthesis. Concurrently, a Density-Functional/Basin-Hopping computational algorithm is employed to locate the low-energy configurations of free Au24Pd1 cluster. Cage structures surrounding a single core atom are found to be favored, with a preference for Pd to occupy the core site. The degree of electron transfer from the Pd dopant to Au is quantified through a Löwdin charge analysis, providing evidence that a single dopant of Pd may act as an electron promoter to the surrounding Au atoms when they are involved in the aerobic oxidation of benzyl alcohol. The study aims to bridge the gap between theoretical and experimental analysis of doped nanoclusters in order to gain a better understanding on their enhanced catalytic in comparison with their monometallic counterparts.