Ambient pressure X-ray photoelectron spectroscopy during electrochemical promotion of ethylene oxidation over a bimetallic Pt–Ag/YSZ catalyst

The electrochemical promotion of the C2H4 + O2 reaction over a bimetallic Pt/Ag catalyst (Pt:Ag ratio ≈ 1.5) interfaced to yttrium stabilized zirconia (YSZ) has been studied at 0.25 mbar and T = 650 K using X-ray photoelectron spectroscopy as in situ method. Applying a positive potential of 2 V causes a relative rate increase in the CO2 production up to 120%; the electrocatalytic promotion effect is non-Faradaic (Λ ≈ 2). An electrochemical promotion is found to occur only at high enough p(C2H4) when a carbonaceous CHx layers builds up inhibiting O2 adsorption. The CHx film is estimated to be about 5–6 layers thick. Only at low p(C2H4), the application of an electric potential causes a decrease in the carbon signal associated with a growth of the O1s signal at 529.3 eV. The latter species can be assigned to an electrochemically generated oxygen spillover species at Ag sites.