(476d) Gold Bimetallic Nanoparticles for Applications in Selective Oxidation Catalysis

Gold nanoparticles have demonstrated catalytic activity and excellent selectivity for various oxidation reactions such as carbon monoxide oxidation, benzyl alcohol oxidation, and propene epoxidation. The activity and selectivity of gold nanoparticles can be further tuned by adding a second metal to the system creating a bimetallic nanoparticle. As an example, recent work from Hutchings et al. has demonstrated the activity of bimetallic AuPd in direct methane partial oxidation.^{1, 2}

Building off of successes in partial oxidation reactions with gold and gold-alloy nanoparticles,^1-4this work demonstrates new synthetic methods for producing small bimetallic clusters with gold. In small particles, there are a large fraction of surface atoms that are undercoordinated, and it is believed in many systems that the undercoordinated sites are the most catalytically active sites. Our new method uses a facile one-pot synthesis where copper and nickel have been used to alloy with gold in our materials to produce bimetallic clusters with triphenylphosphine as the bound ligand. These particles also stable when deposited onto support materials such as titania and silica. As a comparison, this work also synthesizes supported nanoparticles consisting gold alloyed with copper or nickel synthesized using strong electrostatic adsorption (SEA) methods. While the synthesis of some bimetallic nanoparticles using SEA methods has been demonstrated, catalytic testing of these materials largely has not been investigated. This work takes the SEA method-synthesized gold alloy bimetallic nanoparticles and uses them as catalysts for oxidation reactions such as benzyl alcohol oxidation and CO oxidation.

HAADF-STEM confirms that the alloyed nanoparticles are sub-3 nm synthesized via strong electrostatic adsorption and sub-1 nm for the clusters synthesized in solution. Liquid phase batch reactions analyzed with were conducted for benzyl alcohol oxidation with aliquots removed and analyzed via GC. Gas phase CO oxidation activity was measured using an in-line GC-MS. XPS and ICP-MS were utilized to determine the composition of bimetallic nanoparticles and result in the prescribed ratio of metals. Combining the characterization data and the catalysis data, relationships between the catalyst structure and composition have been developed for these oxidation reactions and will be presented. These results help to inform the design of bimetallic catalysts for important these and other important oxidation reaction systems.

References

1. C. Williams, J. H. Carter, N. F. Dummer, Y. K. Chow, D. J. Morgan, S. Yacob, P. Serna, D. J. Willock, R. J. Meyer, S. H. Taylor and G. J. Hutchings, ACS Catalysis, 2018, 8, 2567-2576.
2. N. Agarwal, S. J. Freakley, R. U. McVicker, S. M. Althahban, N. Dimitratos, Q. He, D. J. Morgan, R. L. Jenkins, D. J. Willock, S. H. Taylor, C. J. Kiely and G. J. Hutchings, Science, 2017, 358, 223-227.
3. A. Maclennan, A. Banerjee, Y. Hu, J. T. Miller and R. W. J. Scott, ACS Catalysis, 2013, 3, 1411-1419.
4. M. O. Nutt, J. B. Hughes and M. S. Wong, Environmental Science & Technology, 2005, 39, 1346-1353.