Spatial distribution of cerium valence in model planar Pd/Ce0.7Zr0.3O2 catalysts

Schematic of the spatial distribution of Ce3+ (in green) following Pd-catalyzed H2 reduction of Ce0.7Zr0.3O2, obtained by direct STEM/EELS measurements on a model planar catalyst. [Display omitted] ► The spatial distribution of Ce3+ in a model planar Pd/Ce0.7Zr0.3O2 catalyst, following reduction in H2, was measured by STEM/EELS. ► Spherical reduction zones were found beneath each Pd particle, consistent with a Pd-catalyzed, oxygen anion diffusion-limited bulk oxide reduction process. ► Evidence was also found for a more extended surface reduction process, possibly associated with hydrogen spillover from the Pd particles. The spatial distribution of cerium valence in H2-reduced model planar Pd/Ce0.7Zr0.3O2 catalysts was determined by electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM). Spherical reduction zones were found beneath each Pd particle, consistent with a Pd-catalyzed, oxygen anion diffusion-limited bulk oxide reduction process. Evidence was also found for a more extended surface reduction process, possibly associated with hydrogen spillover from the Pd particles.