TY - JOUR
T1 - Dendrimer templates for heterogeneous catalysts
T2 - Bimetallic Pt-Au nanoparticles on oxide supports
AU - Auten, Bethany J.
AU - Lang, Huifang
AU - Chandler, Bert D.
N1 - Funding Information:
We gratefully acknowledge the Robert A. Welch Foundation (Grant number W-1552) and the U.S. National Science Foundation (Grant number CHE-0449549) for financial support of this work. BJA also thanks the Welch Foundation's Departmental Grant program (W-0031) for a summer stipend and the Beckman Foundation for support during the academic year. Acknowledgement is made to the donors of the American Chemical Society's Petroleum Research Fund for supporting the purchase of the CO oxidation reactor system.
PY - 2008/6/24
Y1 - 2008/6/24
N2 - Polyamidoamine (PAMAM) dendrimers were used to template Pt, Au, and bimetallic Pt-Au dendrimer encapsulated nanoparticles (DENs) in solution. Adjusting the solution pH allowed for slow, spontaneous adsorption of the nanoparticles onto silica, alumina, and titania. After dendrimer removal, the catalysts were characterized with infrared spectroscopy of adsorbed CO and tested with CO oxidation catalysis. Infrared spectroscopy of the monometallic Pt catalysts showed a slight shift in the CO stretching frequency for the different supports. For the bimetallic catalysts, infrared spectra showed CO adsorbed on both Pt and on Au sites. Spectra collected during CO desorption showed substantial interactions between the two bands, confirming the presence of bimetallic particles on all the supports. The bimetallic catalysts were found to be more active than the monometallic catalysts and had lower apparent activation energies. The titania supported Pt-Au catalyst was resistant to deactivation during an extended treatment at 300 °C. Correlations between IR spectra and catalytic activity showed differences between the mono- and bimetallic materials and implicated a bimetallic Pt-Au ensemble at the catalytic active site. This is the first study to show that DENs are appropriate precursors for studying support effects on catalysis by metal nanoparticles, although the magnitude of the effects were small.
AB - Polyamidoamine (PAMAM) dendrimers were used to template Pt, Au, and bimetallic Pt-Au dendrimer encapsulated nanoparticles (DENs) in solution. Adjusting the solution pH allowed for slow, spontaneous adsorption of the nanoparticles onto silica, alumina, and titania. After dendrimer removal, the catalysts were characterized with infrared spectroscopy of adsorbed CO and tested with CO oxidation catalysis. Infrared spectroscopy of the monometallic Pt catalysts showed a slight shift in the CO stretching frequency for the different supports. For the bimetallic catalysts, infrared spectra showed CO adsorbed on both Pt and on Au sites. Spectra collected during CO desorption showed substantial interactions between the two bands, confirming the presence of bimetallic particles on all the supports. The bimetallic catalysts were found to be more active than the monometallic catalysts and had lower apparent activation energies. The titania supported Pt-Au catalyst was resistant to deactivation during an extended treatment at 300 °C. Correlations between IR spectra and catalytic activity showed differences between the mono- and bimetallic materials and implicated a bimetallic Pt-Au ensemble at the catalytic active site. This is the first study to show that DENs are appropriate precursors for studying support effects on catalysis by metal nanoparticles, although the magnitude of the effects were small.
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U2 - 10.1016/j.apcatb.2007.12.012
DO - 10.1016/j.apcatb.2007.12.012
M3 - Article
AN - SCOPUS:44749090349
SN - 0926-3373
VL - 81
SP - 225
EP - 235
JO - Applied Catalysis B: Environmental
JF - Applied Catalysis B: Environmental
IS - 3-4
ER -