Ethanol oxidation at Pt-based alloys and UPD modified Pt/C catalysts

Abstract

Activity of two alloys, Pt3Sn/C and Pt3Ru2/C, was compared with the activity of Pt/C modified with corresponding amounts of SnUPD (~25 %) and RuUPD (~40 %) in overall oxidation of ethanol. Pt3Sn/C, Pt3Ru2/C and Pt/C catalysts were characterized by XRD. To establish the activity and stability of the catalysts potentiodynamic, quasi steady-state and chronoamperometric measurements were performed. Both alloys are more active than SnUPD or RuUPD modified Pt/C catalysts. Electronic effect determining dominantly the activity of Pt3Sn/C is the main reason for its higher activity compared to Pt3Ru2/C. Since SnUPD and RuUPD do not provoke any significant modification of electronic environment, both modified Pt/C catalysts are less active than corresponding alloys. More pronounced difference in activity between Pt3Sn/C and SnUPD modified Pt/C than between Pt3Ru2/C and RuUPD modified Pt/C is caused by electronic effect in Pt3Sn/C. High activity of Pt3Sn/C modified with small amount of SnUPD (~10%) can be explained by combining the electronic effect, causing less strongly bonded adsorbate on Pt sites and easier mobility of SnUPD, with enhanced amount of oxygen-containing species on Sn sites resulting finally in reinforcement of bifunctional mechanism.