Spatial distribution of cerium valence in model planar Pd/Ce 0.7Zr0.3O2 catalysts

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.