title: Single Pd Atoms on θ-Al2O3(010) Surface do not Catalyze NO Oxidation.
abstract: New convenient wet-chemistry synthetic routes have made it possible to explore catalytic activities of a variety of single supported atoms, however, the single supported atoms on inert substrates (e.g. alumina) are limited to adatoms and cations of Pt, Pd, and Ru. Previously, we have found that single supported Pt atoms are remarkable NO oxidation catalysts. In contrast, we report that Pd single atoms are completely inactive for NO oxidation. The diffuse reflectance infra-red spectroscopy (DRIFTS) results show the absence of nitrate formation on catalyst. To explain these results, we explored modified Langmuir-Hinshelwood type pathways that have been proposed for oxidation reactions on single supported atom. In the first pathway, we find that there is energy barrier for the release of NO2which prevent NO oxidation. In the second pathway, our results show that there is no driving force for the formation of O=N-O-O intermediate or nitrate on single supported Pd atoms. The decomposition of nitrate, if formed, is an endothermic event.
authors.affiliation: Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6133, USA. narulack@ornl.gov.
authors.forename: Chaitanya K
authors.identifier: http://orcid.org/0000-0001-5739-589X
authors.initials: CK
authors.lastname: Narula
authors.affiliation: Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6133, USA.
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Allard
authors.affiliation: Energy & Transportation Science Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Melanie
authors.identifier: http://orcid.org/0000-0003-0382-0824
authors.initials: M
authors.lastname: Moses-DeBusk
authors.affiliation: Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831-6133, USA.
authors.forename: G Malcom
authors.initials: GM
authors.lastname: Stocks
authors.affiliation: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA.
authors.forename: Zili
authors.initials: Z
authors.lastname: Wu
mesh_terms: D000537:Aluminum Oxide / Q000737:chemistry*; D002384:Catalysis; D008958:Models, Molecular; D008962:Models, Theoretical; D009569:Nitric Oxide / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010165:Palladium / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties
chemical_list: D009569:Nitric Oxide; D010165:Palladium; D000537:Aluminum Oxide; D010100:Oxygen