P123-stabilized Au–Ag alloy nanoparticles for kinetics of aerobic oxidation of benzyl alcohol in aqueous solution

Colloidal Au–Ag alloy nanoparticles with various Ag/Au molar ratios were first prepared by a co-reduction method in P123 aqueous solution and characterized by UV–vis, TEM, and XPS. The prepared Au–Ag alloy nanoparticles were substantially stable and had comparable particle sizes (3–4 nm) for aerobic oxidation kinetics of benzyl alcohol. The addition of Ag not only significantly enhanced the reaction rate but also increased the apparent activation energy (Ea) compared to that for monometallic Au nanocatalysts. The kinetics investigations indicated that on the pure Au sites, the oxidation of benzyl alcohol followed 1.5-order reaction kinetics, while on Au sites adjacent to Ag atoms, it followed 0.5-order reaction kinetics. The presence of Na2CO3 greatly improved the catalytic activity of Au–Ag nanocatalysts but decreased the selectivity to benzaldehyde.

Graphical abstractAu–Ag alloy nanoparticles were synthesized as catalysts for aerobic oxidation of benzyl alcohol in aqueous solution. The alloying of Au with Ag can significantly enhance the oxidation rate of benzyl alcohol and result in different reaction mechanisms and kinetics from pure Au. On the active sites with Au alone, the oxidation of benzyl alcohol follows 1.5-order reaction kinetics while on Au active sites adjacent to Ag atoms, 0.5-order reaction with respect to benzyl alcohol.Figure optionsDownload full-size imageDownload high-quality image (100 K)Download as PowerPoint slideHighlights► Stable Au–Ag alloy nanoparticles having comparable particle sizes (3–4 nm) are first prepared in P123 aqueous solution. ► The Au–Ag nanoparticles show certain activity for aerobic oxidation of benzyl alcohol without added base. ► The synergistic effect between Ag and Au significantly improves the catalytic activity of Au particles. ► On the mere Au sites, the oxidation follows 1.5-order while on Au sites adjacent to Ag atoms 0.5-order. ► The presence of base improves the catalytic activity of Au–Ag particles, but decreases the selectivity to benzaldehyde.