Platinum depletion layer

Strong evidence of delayed oxidation of a Pt monolayer on Pd nanoparticles in comparison with the oxidation of Pt nanoparticles was obtained from in situ XANES measurements as a function of potential. Figure 3a shows the Pt L3 edge spectra obtained on the PtML/Pd/C electrocatalysts at four different potentials. Only at the highest potentials is there an increase in the intensity of white line as a consequence of the PtOH formation causing a depletion of Pt s d-band. The increase in the intensity of the white line for the Pt/C electrocatalyst commences at considerably less positive potentials (Fig. 3b, c). This indicates that the oxidation of a Pt mono-layer on palladium substrate requires higher potentials than that of platinum nanoparticles on a carbon substrate, which is in accord with the voltammetry data [3]. 

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