Automotive catalysis is more complicated than most applications of catalysts, because of the complex and dynamic changes in the exhaust gas environment. The ability to create highly dispersed, single-site catalysts, which are highly efficient and have low cost, is very much desirable [1]. While single atom sites can be created, there is still disagreement over whether the single atom sites are indeed catalytically active or if the observed catalytic activity of single-site catalysts is due to metal nanoparticles either unobserved during initial microscopy studies or formed upon exposure to catalytic conditions [2]. Such disagreements create a crucial need for the development of well-defined single-site catalysts with an accurate theoretical model in order to correctly determine the chemical nature of the catalytically active sites. To this end, we have studied low-temperature CO oxidation on Pt single-site catalysts supported on the “29” Cu surface oxide. The “29” Cu surface oxide is a high coverage chiral structure. Through the use of scanning tunneling microscopy (STM), CO temperature programmed desorption (TPD), and density functional theory (DFT) techniques, we determined that an accurate model for the “29” Cu oxide surface is formed from the growth of a CuxO layer formed from 6 fused hexagonal rings above the Cu (111) surface where 5 oxygen adatoms are added at the center of the CuxO rings [3]. Furthermore, the state of the Pt single atoms before, during, and after the reaction is determined through a combination of theoretical and experimental techniques. During catalysis, CO2 forms from the combination of an oxygen from the “29” Cu oxide surface with the CO adsorbed on the Pt single atoms. Moreover, as recent experiments have found oxidized Pt/Cu(111) single atom alloys to be reducible under hydrogen, DFT calculations were carried out to investigate this phenomena using our “29” oxide model with a Pt atom alloyed into the underlying Cu(111) substrate. Dissociative adsorption of hydrogen over this surface was found to be unfavorable as compared to unoxidized Pt/Cu(111) single atom alloys. Upon further analysis, we attribute this to the differing electronic structures of the Cu atoms surrounding the alloyed Pt, which demonstrates the impact of the surrounding oxide over Pt/Cu(111) single atom sites.

Elucidating the chemical nature of single-site catalysts from first principles

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.