Performances of Pd-Me (Me = Ag, Pt) catalysts in the direct synthesis of H2O2 on catalytic membranes

The performances in the direct synthesis of hydrogen peroxide (H2O2) with Pd-Me (Me = Ag, Pt) catalysts prepared by depositing the noble metals by electroless plating deposition (EPD) or deposition–precipitation (DP) methods on α-Al2O3 asymmetric ceramic membrane with or without a further surface coating by a carbon thin layer are reported. The effect of the second metal with respect to Pd-only catalysts considerably depends on the presence of the carbon layer on the membrane support. On ceramic membranes the use of Pd-Ag bimetallic catalysts avoids the formation of β-PdH and improves the catalytic performances, while in the case of Pd-Pt bimetallic catalysts small defective nanoparticles are formed which catalyze the unselective formation of water. Conversely, on carbon-coated membranes the latter effect is not present and good H2O2 productivities and selectivities are shown for the Pd-Pt bimetallic systems, in particular those synthesized with the EPD method, although for both types of preparations the Pd-Pt bimetallic catalyst show improved behavior with respect to Pd-only systems.