PT  - JOURNAL ARTICLE
AU  - Lei, Y.
AU  - Mehmood, F.
AU  - Lee, S.
AU  - Greeley, J.
AU  - Lee, B.
AU  - Seifert, S.
AU  - Winans, R. E.
AU  - Elam, J. W.
AU  - Meyer, R. J.
AU  - Redfern, P. C.
AU  - Teschner, D.
AU  - Schlögl, R.
AU  - Pellin, M. J.
AU  - Curtiss, L. A.
AU  - Vajda, S.
TI  - Increased Silver Activity for Direct Propylene Epoxidation via Subnanometer Size Effects
AID  - 10.1126/science.1185200
DP  - 2010 Apr 09
TA  - Science
PG  - 224--228
VI  - 328
IP  - 5975
4099  - http://science.sciencemag.org/content/328/5975/224.short
4100  - http://science.sciencemag.org/content/328/5975/224.full
SO  - Science2010 Apr 09; 328
AB  - Production of the industrial chemical propylene oxide is energy-intensive and environmentally unfriendly. Catalysts based on bulk silver surfaces with direct propylene epoxidation by molecular oxygen have not resolved these problems because of substantial formation of carbon dioxide. We found that unpromoted, size-selected Ag3 clusters and ~3.5-nanometer Ag nanoparticles on alumina supports can catalyze this reaction with only a negligible amount of carbon dioxide formation and with high activity at low temperatures. Density functional calculations show that, relative to extended silver surfaces, oxidized silver trimers are more active and selective for epoxidation because of the open-shell nature of their electronic structure. The results suggest that new architectures based on ultrasmall silver particles may provide highly efficient catalysts for propylene epoxidation.