The most common method of preparing supported metal catalysts begins by impregnating a porous oxide or carbon with an aqueous solution of dissolved metal complexes. The goal of most preparations is to convert the deposited precursor, often a coordination complex, into small metal particles firmly anchored onto the high surface area support. For a given amount of metal, the smaller the metal particles, the more catalytically active sites are created. In promoted or bimetallic catalysts, the goal is normally to maximize contact of the metal and promoter, or the two metals. How to achieve this effectively is the subject of many studies, both academic and industrial.In many cases these preparation steps are considered to be art.
Professor John Regalbuto of the University of South Carolina has been effectively studying the fundamental phenomena that occur during supported metal catalyst impregnation, striving to transform the art of catalyst preparation into a science. With past support from NSF his research group has described the uptake of noble and base metal coordination complexes over many oxides and carbons during impregnation in terms of a simple electrostatic mechanism leading to an optimal pH at which the precursor-surface interaction is strongest. Fundamental aspects of the other preparation steps of these monometallic catalysts have also been studied. In this proposal, the strong electrostatic adsorption approach will be applied to the most complicated but highest impact preparations - bimetallic catalysts. Regalbuto postulates that this approach will yield unprecedented control of the morphology of bimetallic catalysts prepared with real, high surface area supports using common, commercially available metal precursors. Specifically, he hypothesizes that core-shell morphologies can be prepared by selectively adsorbing one metal precursor complex onto the oxide form of a second metal, and that core-shell morphology will be retained with low reduction temperatures and alloys will form at higher temperatures. Another alternative application of the science approach predicts that homogeneous alloys can be prepared with low temperature reductions by coadsorbing metal complexes in a single adsorption step.
It is hoped that successful demonstrations of the proposed work will lead to a transformation in the understanding and practice of bimetallic catalyst preparation. The potential scientific impact is extremely broad, affecting all facets of the chemical industry which employ bimetallic catalysts. With that target, this award is a GOALI award. Regalbuto has teamed with the Johnson Matthey Technical Centre in Sonning, UK, a world leading company in noble metal catalyst manufacture. Measurements of point of zero charge and adsorption surveys over a wide range of noble metal oxides will be made for the first time at JMTC as well as at the University of South Carolina. Strategically, the partnership with industry will allow access to the copious amounts of noble metal oxides needed for the fundamental studies of adsorption properties.
The project work has been formulated specifically for REU students; this work will be relatively easy to undertake, exciting to do, and will get noticed in peer reviewed publications and conference presentations. In addition the PI will tie into the comprehensive portfolio of outreach and diversity programs offered at USC: the Louis Stokes Alliance for Minority Participation, the SC Alliance for Minority Participation, and the South East Alliance for Graduate Education.
