Directed synthesis of well dispersed and highly active AuCu and AuNi nanoparticle catalysts

Abstract

Controlled synthesis of bimetallic catalysts has attracted much attention in heterogeneous catalysis because their catalytic activity often depends on their size and structure. Traditional modification methods have no control over the deposition of the first metal, but concentrate on using the dispersion of the first metal to control the deposition of the second metal, resulting in the deficiency in controlling the dispersion of final bimetallic catalysts. In this work, one new method was proposed to control the synthesis of supported bimetallic AuCu and AuNi catalysts by controlling the dispersion of both the first metal and second metal. The first metal (Cu or Ni) of bimetallic nanoparticles was well dispersed as a configurational ion of hydrotalcites (HTs), which interacted with the other metal (Au) of bimetallic nanoparticles by a spontaneous redox and alloying reaction. The good dispersion of the first metal controlled the good dispersion of the final bimetallic nanoparticles through the interaction between the two metals. The size, structure and composition of bimetallic nanoparticles were characterized using X-ray diffraction (XRD), nitrogen physisorption, X-ray photoelectron spectroscopy (XPS) and scanning transmission electron microscopy (STEM) techniques. The mean sizes of the bimetallic nanoparticles were 1.9 nm for AuCu and 2.8 nm for AuNi, which were much smaller than that prepared by traditional methods (>8.7 nm). The catalytic activity of AuCu and AuNi nanoparticles in the aerobic oxidation of benzyl alcohol was tested, which showed far higher activity than those prepared by traditional methods.