Synergistically Activated Pd Atom in Polymer-Stabilized Au<sub>23</sub>Pd<sub>1</sub> Cluster.

Hasegawa, Shingo; Masuda, Shinya; Takano, Shinjiro; Harano, Koji; Kikkawa, Jun; Tsukuda, Tatsuya · ACS Nano · 2022

basic_science · Level V

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Abstract

Single Pd atom doped Au<sub>23</sub>Pd<sub>1</sub> clusters stabilized by polyvinylpyrrolidone (Au<sub>23</sub>Pd<sub>1</sub>:PVP) were selectively synthesized by kinetically controlled coreduction of the Au and Pd precursor ions. The geometric structure of Au<sub>23</sub>Pd<sub>1</sub>:PVP was investigated by density functional theory calculation, aberration-corrected transmission electron microscopy, extended X-ray absorption fine structure analysis, Fourier transform infrared spectroscopy of adsorbed CO, and hydrogenation catalysis. These results showed that Au<sub>23</sub>Pd<sub>1</sub>:PVP takes polydisperse but the same atomic arrangements as undoped Au<sub>24</sub>:PVP while exposing all the atoms including the Pd atom on the surface. Au<sub>23</sub>Pd<sub>1</sub>:PVP exhibited a significantly higher catalytic activity than Au<sub>24</sub>:PVP for the aerobic oxidation of <i>p</i>-substituted benzyl alcohols. The kinetic studies showed that the rate-determining step was the hydride abstraction from the α-carbon of the alkoxides for both systems. The activation energy for hydride abstraction by Au<sub>23</sub>Pd<sub>1</sub>:PVP was lower than that by Au<sub>24</sub>:PVP, indicating that the doped Pd atom acts as the active center.