471191 Supported, Homogeneously Alloyed Bimetallic Nanoparticles By Electrostatic Adsorption

Thursday, November 17, 2016: 9:50 AM
Franciscan A (Hilton San Francisco Union Square)
Andrew Wong1, Qiuli Liu1 and John R. Regalbuto2, (1)Chemical Engineering, University of South Carolina, Columbia, SC, (2)Department of Chemical Engineering, University of South Carolina, Columbia, SC

Bimetallic catalysts are often important for chemical reactions due to their enhanced performance over monometallic catalysts [1]. Incorporating a secondary metal into a system can benefit the catalytic system through ensemble, bifunctional, and electronic effects. The most prevalent method for synthesizing supported catalysts is dry impregnation (DI), also known as incipient wetness, in which a solution containing a specific amount of metal precursor is added to just fill the pore volume of the support [2]. While the procedure is simple and the metal loading is precisely known, limitations of DI preparations often include larger particle sizes and less intimate metal-support interactions. Moreover, bimetal catalysts produced through DI often exhibit a poor degree of alloying between the metals.

Our goal was to demonstrate a simple, effective method to synthesize highly dispersed, well alloyed bimetallic nanoparticles using strong electrostatic adsorption (SEA). SEA is achieved by charging the support by controlling the pH of the solution. A metal precursor that is oppositely charged can then be adsorbed onto the surface of the charged support. Using a simultaneous adsorption of either two cationic or anionic precursors allows excellent bimetallic interactions. The combinations of multiple bimetallic systems (Cu, Co, Ni, Pd, and Pt) prepared by SEA were compared to equivalent DI catalysts. Particle sizes and the degree of alloying were determined through electron micrographs, elemental mapping of nanoparticles, and powder XRD.

Results from XRD show the bimetallic catalysts produced by SEA were highly dispersed (<2 nm), while the DI catalysts exhibited large XRD peaks (>5nm). Initial elemental maps and STEM images indicate the SEA catalysts had a higher degree of alloying compared to the DI catalyst, and particle agglomeration was avoided for the SEA catalyst. A complete comparison of the bimetal systems prepared by DI and SEA will be discussed.

References

[1] Sankar, M., et al. (2012). "Designing bimetallic catalysts for a green and sustainable future." Chemical Society Reviews 41(24): 8099-8139.

[2] Cho, H.-R. and J. R. Regalbuto (2015). "The rational synthesis of Pt-Pd bimetallic catalysts by electrostatic adsorption." Catalysis today 246: 143-153.


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