(3cg) Synthetic and Spectroscopic Methods to Facilitate Design of Highly Selective Catalytic Sites

Increasing energy costs and environmental concerns have increased the demand for highly selective and recyclable catalysts to eliminate costly purification steps and reduce waste and byproduct formation.  The nature of selective sites can be probed with advanced spectroscopic methods to determine structure-function relationships.  Investigating these relationships and creating synthetic methods to increase the number of highly selective sites are of paramount importance to achieving more selective and active catalysts.

My PhD research experience involved a plasma-based aerosol synthesis method for nanoparticles and characterization of nanomaterials.  The limited ability of current technology to determine nanoparticle size in situ led me to design, build, simulate, and validate the nano-RDMA, a new instrument capable of classifying nanoparticle size in the one to ten nanometer size range.  The instrument performance permitted in situinvestigation of size effects on surface dehydrogenation of silicon nanoparticles, demonstrating a lower activation barrier for dehydrogenation from small clusters.  Additionally, the capabilities of the instrument were tested through demonstrating the sputter production of atomic clusters (<1 nm in size) from an atmospheric plasma source.  While the resolving power was substantial, the simulation results allowed design of a second generation instrument that has a factor of four improvement in resolution.

In addition to synthesizing and characterizing nanoparticles, my research involved designing, building, and characterizing an electrospray source that was used to incorporate platinum nanoparticles in membrane electrode assemblies (MEAs) for low catalyst loading, solid acid fuel cell applications.  The electrospray source produced crystallites of the fuel cell membrane material on the scale of 100 nanometers – smaller than ever produced before – while simultaneously mixing platinum nanoparticles to create the MEA.  The reduced size discrepancy between the catalyst particle (i.e. 10 nm) and the membrane material permitted low catalyst loading for the fuel cell.

My post-doctoral research examines the cooperativity between acid and organic base sites in bio-inspired cooperative catalysis.  In enzymes, the catalytic active site is organized through a complex architecture to have (1) tuned interactions between acid and base groups, and (2) precise spatial organization.  Through designed immobilization of acid and base sites on a rigid support, these beneficial aspects can be integrated into simpler materials, permitting the ability to design-in catalytic cooperativity at the nanoscale.  Catalytic testing has shown that decreasing the acid-base interaction through using a weaker acid accelerates the rate of reaction.  Additionally, the spatial organization of the active site proved important with longer more flexible linkers resulting in highly cooperative catalysts.

Integrating my background of instrumentation design, material synthesis, and catalysis, my future research will seek to control material functionality for applications in the fields of energy, catalysis, and advanced functional materials.  Characterizing surface properties will elucidate properties that are responsible for catalyst selectivity, requiring new techniques and associated instrumentation to probe subtle yet significant changes that occur.  The integrated and multidisciplinary probing of materials properties will lead to fundamental discoveries of structure function relationships that can be utilized to synthesize more selective and active catalytic materials.

Post-doctoral Advisor: Christopher W. Jones, Georgia Institute of Technology, School of Chemical & Biomolecular Engineering

Doctoral Thesis Committee: Professors Konstantinos P. Giapis, Richard C. Flagan, Sossina M. Haile, and J. L. Beauchamp, California Institute of Technology, Division of Chemistry and Chemical Engineering

Publications:

[1] N.A. Brunelli, R.C. Flagan, K.P. Giapis, Aero. Sci. Tech. 2009, 43, 53-59.

[2] A. Varga, N.A. Brunelli, M. Louie, K. P. Giapis, S.M. Haile, J. Mater. Chem. 2010, 20, 6309-6315.

[3] J. Jiang, M. Attoui, M. Heim, N.A. Brunelli, P. McMurry, G. Kasper, R.C. Flagan, K.P. Giapis, and G. Mouret, Aero. Sci. Tech. 2011, 45, 48-492.

[4] N. A. Brunelli, W. Long, K. Venkatasubbaiah, C. W. Jones, Top. Catal. 2012 (in review).

[5] J. Thompson, C. Blad, N. A. Brunelli, M. Leydon, R. Lively, C. W. Jones, S. Nair, Chem. Mater. 2012 (in press).

[6] N. A. Brunelli, K. Venkatasubbaiah, C. W. Jones, Chem. Mater. 2012 (in review).

[7] N. A. Brunelli, S. A. Didas, K. Venkatasubbaiah, C. W. Jones, (in preparation).

[8] N. A. Brunelli, E. L. Neiholdt, K. P. Giapis, R. C. Flagan, J. L. Beauchamp, (in preparation).