Aerobic Oxidation of Cyclohexane on Catalysts Based on Twinned and Single-Crystal Au₇₅Pd₂₅Bimetallic Nanocrystals

Abstract

Bimetallic Au75Pd25 nanocrystals with shapes of icosahedron and octahedron were synthesized by adding different amounts of iodide ions, and were employed as catalysts for solvent-free aerobic oxidation of cyclohexane. Although both icosahedrons and octahedrons were bounded by {111} facets, the turnover frequency number of Au75Pd25 icosahedrons reached 15,106 h(-1), almost three times as high as that of Au75Pd25 octahedrons. The conversion of cyclohexane reached 28.1% after 48 h using Au75Pd25 icosahedrons, with the selectivity of 84.3% to cyclohexanone. Density functional theory calculations along with X-ray photoelectron spectroscopy examinations reveal that the excellent catalytic performance of AuPd icosahedrons could be ascribed to twin-induced strain and highly negative charge density of Au atoms on the surface.