The application of the EQCM data analysis for the examination of surface oxide formation on Pt-Pd-Ru ternary alloys

The stoichiometry of surface oxides, formed on Pt-Pd-Ru alloys in 0.5 M H2SO4 aqueous solutions, was postulated on the basis of cyclic voltammetric (CV) and the electrochemical quartz crystal microbalance (EQCM) measurements. A procedure of data analysis was elaborated to extract the information on surface oxide properties from the correlations between the EQCM frequency changes and electric charge. The average values of metal oxidation state in the oxides depend on potential of their formation, alloy composition and degree of alloy homogeneity. The highest metal oxidation state (+8) was reached for 10 %Pt-25 %Pd-65 % Ru alloy, while the lowest one (+4) for 35 %Pt-26 %Pd-38 %Ru alloy. Preliminary hydrogen electrosorption on Pd-rich (63 %) or Ru-rich (65 %) Pt-Pd-Ru alloys resulted in a decrease in the average metal oxidation states in surface oxides, whereas for other alloys the influence of hydrogen treatment was negligible