Pd/ZnO/Al₂O₃ catalysts have been shown to be highly active for methanol steam reforming and selective towards production of CO₂ and H₂. Previous work has shown that PdZnO catalysts prepared from an acidic precursor can etch the support, destroying the faceted morphology of the ZnO support, and leading to a decrease in activity. Preserving the ZnO facets through use of an organic precursor leads to improved catalytic activity. It is not clear wether ZnO participates in this reaction through a bifunctional pathway. This work addresses the role of ZnO by systematically investigating the catalytic activity of samples prepared from faceted ZnO of differing morphology (nanorods and platelets), etched and reprcipitated ZnO, and ZnAl₂O₄. Pd deposition on each support was carried out by using incipient wetness with a Pd(OAc)₂ precursor. An alternative catalyst preparation using preformed nanoparticles was also investigated. We used CO oxidation activity to quantitatively determine the number of active Pd sites, and methanol steam reforming (after forming PdZn particles in-situ). These results show that the ZnO surface morphology plays a significant role in afecting the reactivity of Pd based steam reforming catalysts.

This work has been supported by the United States Department of Energy, Office of Basic Energy Sciences under contract number DE-FG02-05ER15712 (University of New Mexico) and DE-AC0494AL85000 (Sandia National Laboratories). Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy.