Bimetallic Ag–Au/SiO2 catalysts: Formation, structure and synergistic activity in glucose oxidation

Abstract

SiO 2 supported Ag-Au bimetallic catalysts were prepared by sol adsorption method with 10/90, 20/80, 33/67, and 50/50 Ag/Au molar ratios. Reduction of HAuCl 4 in Ag sol resulted in alloyed AgAu colloid particles and that structure remained after calcination and reduction treatment. The alloy structure of the catalysts was confirmed by UV-visible spectroscopy and high resolution transmission electron microscopy. The Au-Ag bimetallic effect and its dependence on the Ag/Au molar ratio was studied in glucose oxidation where synergistic activity increase was observed compared to the Au/SiO 2 reference sample in case of the bimetallic samples with less than Ag/Au=50/50 molar ratio. The Ag/SiO 2 was inactive at the same conditions. The Ag/Au surface atomic ratios -calculated by X-ray photoelectron spectroscopy (XPS) -were slightly higher than in the bulk -determined by prompt gamma activation analysis (PGAA). The higher activity of the bimetallic samples is suggested to be caused by the improved O 2 activating ability provided by Ag sites. The further increase of Ag loading above the optimal concentration may dilute or cover the Au to such an extent that the number of gold ensembles necessary for glucose activation decreases deteriorating the activity.

Au–Ag/CeO2 and Au–Cu/CeO2 Catalysts for Volatile Organic Compounds Oxidation and CO Preferential Oxidation

“…Au-Cu was one of the most investigated bimetallic system with several examples of excellent performance reported both for selective oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylicacid [23], for CO oxidation [24] and CO-PROX [25]. Au-Ag catalysts also received considerable attention in the literature for glucose oxidation [26], CO oxidation [27] and CO-PROX [28].…”

Alginate fibers embedded with silver nanoparticles as efficient catalysts for reduction of 4-nitrophenol

“…[6][7][8] Consequently, it is desirable to explore simple and effective methods to maintain the longterm stability so as to determine the catalytic performance of AgNPs. [17][18][19][20][21] Lu et al reported on the in situ synthesis of AgNPs onto polystyrene (PS) core-poly(acrylic acid) (PAA) polyelectrolyte brush particles. [9][10][11][12] Hybrid catalysts integrated AgNPs with inorganic and organic supports have been successfully developed.…”

Chemical Preparation of Supported Bimetallic Catalysts. Gold-Based Bimetallic, a Case Study

“…Interestingly, electron microscopy revealed that the particles in Au-Pd/TiO 2 remained bimetallic after H 2 or after O 2 then H 2 treatment whereas those in Au-Rh/TiO 2 , turned Janus-type after H 2 treatment, and tended to segregate into two separate phases with small Rh particles and larger Au ones after O 2 then H 2 treatment (Figure 4). PVA was also used to stabilize Au-Ag colloids but first with the synthesis of PVA-stabilized Ag to avoid AgCl precipitation then the addition of HAuCl 4 and PVA followed by NaBH 4 [71]. Adsorption of the Au-Ag colloids on TiO 2 was assisted by poly(diallyldimethylammonium) chloride (PDDA) addition.…”