Selective lactose oxidation in aqueous-phase over Ag-Au bimetallic nanoparticles supported on Al2O3 under mild reaction conditions

DUARTE, H.A.; GARETTO, T.F.; REGENHARDT, S.A.; SEBASTIAN, V.; MEYER, C.I.; ZELIN, J.; MARCHI, A.J.

Molecular Catalysis

Elsevier BV

Año: 2020

2468-8231

In this work, Au-Ag based catalysts supported on Al2O3were prepared by a precipitation-deposition method atcontrolled pH and tested in the selective lactose (LA) oxidation to lactobionic acid (LB) in aqueous phase.Combining XPS and STEM-HAADF, it was found that there is an important surface Ag enrichment of bimetallicnanoparticles for bulk atomic ratios Au/(Au + Ag) > 0.5. These bimetallic nanoparticles were active for theselective LA oxidation into LB and the maximum activity was reached with Au/(Au + Ag) = 0.9. In this case, thesurface Au/(Au + Ag) atomic ratio was about 0.5, which indicates that there is the same amount of both ele-ments at the active surface of the catalyst. Assuming that LA is chemisorbed on Au sites, and O2on Ag ones, thisparticular surface atomic ratio would favor the interaction and reaction between both reactants. Thus, the sy-nergistic effect between Au and Ag could explain the results of this study. A compensation effect betweenfrequency factor and activation energy supports the existence of such synergy. If the atomic ratio is Au/(Au + Ag)≤0.5, a layer of Ag deposits over the Au nanoparticles (core-shell structure) and the conversion of LAinto LB drops to zero