RUI: Preparation and Kinetic Characterization of New Bimetallic Au-M Selective Hydrogenation Catalysts

This award is funded by the Chemical Catalysis Program in the Division of Chemistry. Professors Bert D. Chandler and Christopher J. Pursell of Trinity University are supported to investigate the advantages of combining inexpensive metals with gold (Au) to form bimetallic nanoparticle catalysts. The project addresses the need to find alternatives to scarce and expensive catalysts which are prohibitive to large-scale chemical production. Improving the fundamental understanding of bimetallic nanoparticles and their catalytic properties has the potential to positively impact both the U. S. catalysis industry and the national economy by providing cheaper materials and consumer products as well as reducing pollution and industrial waste. The project involves preparing tailored nanoparticles with an inexpensive metal, such as copper, nickel and iron, at the core and Au on the outside. This includes finding new synthetic means to assemble a few hundred atoms from two metals - which is a challenging chemical synthesis problem. The goals are to evaluate synthetic methods, understand how the inexpensive metal alters the catalytic chemistry of gold, and test the new catalysts for improved performance in some industrially important reactions. Integrating the research with education provides research opportunities for undergraduate students, giving them hands on experience in this nationally important area of research and training them to be the next generation of scientists.

New nanoparticle and catalyst synthesis techniques are being employed to prepare bimetallic nanoparticles on alumina and titania. The primary goal is to take advantage of recent developments in solution nanoparticle synthesis to develop new routes to synthetically challenging bimetallic core-shell nanoparticle catalysts. Kinetics -based analytical techniques are being used to evaluate the new catalysts including (i) intentional poisoning studies to evaluate relative numbers of active sites, (ii) Michaelis-Menten analysis of poisoning experiments to evaluate the effects of thiol poisoning, and (iii) Hammett relationships to probe changes in nanoparticle surface charge. These studies enable new quantitative comparisons between catalysts and allow for assessing heterometals affect the chemistry of Au nanoparticles. In addition, these studies are addressing fundamental questions regarding the nature of the catalytic active sites. This project also expands on a recent discovery of 'broad band IR absorption' for Au/TiO2 catalysts, and uses this phenomenon to characterize the strength of H2 and CO adsorption on the catalysts. These physical characterization studies, combined with detailed kinetics studies, are enabling the development of structure-property-activity relationships that guide researchers in designing the next generation of catalysts. In particular, these studies are (i) providing clear information regarding how Au nanoparticle chemistry and catalysts can be tuned using other transition metals, (ii) testing recent computational models, and (iii) providing insight into potential new applications for Au based catalysts.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.