3.4.3. Confirmation of Pd(poly) surface changes after ORR by height and phase AFM imaging
Fig. 9. AFM images (2 × 2) μm2 of Pd(poly) surfaces obtained immediately after preparation (left column), and after ORR in 0.1 M NaOH (right column) showing: a) surface topography, z-range 25 nm; b) phase image, z-range 30°; c) 51% of oxidized Pd surface in phase image with Panobinostat background set at 0°, d) surface topography, z-range 40 nm; e) phase image, z-range 120°; f) 67% of oxidized Pd surface in phase image with a background set at 0°.Figure optionsDownload full-size imageDownload as PowerPoint slide
In addition, surface topography AFM images of Pd(poly) surface mechanically polished and electrochemically cleaned as described for polycrystalline Pt  and of one obtained after UV/ozone treatment for 10 min (as explored in ref. ) are given in Fig. 10. The estimated surface roughness of such Pd surface, Fig. 10a, is almost two times higher than in the case when Pd is prepared in non-aqueous solution as explored in this work (see Fig. 9a). The image in Fig. 10b, clearly illustrates the change of palladium surface topography after ozone treatment. Surface roughness increases upon ozone treatment to nearly the same extent as during ORR measurements. This example illustrates again the strong influence of the presence of the excess of oxygen in the environment on both surface structure and surface chemistry of polycrystalline palladium. The electrocatalytic activity of ozone treated Pd surface will be further examined in our future work.