| In the recent decades, more demanding catalytic processes have challenged current catalyst technologies. Advances in monometallic catalysts through size and structure modifications have improved catalyst performance, but technological enhancements to monometallic catalysts are nearing exhaustion. One way to further improve catalyst design and function of these monometallic catalysts is through the addition of a secondary metal. Bimetallic catalysts are of great interest due to their increased performance and cost-saving potential when substituting expensive precious group metals for base metals. These bimetallic catalysts often have synergistic properties such as increased activity, selectivity, and stability unobserved in their monometallic counterparts. Therefore work is needed to better understanding how bifunctional, ensemble, and electronic effects aid bimetallic catalyst performance and how improvements to these catalysts can be made through rational catalyst design.;This work focuses on the synthesis, characterization, and evaluation of bimetallic catalysts on oxide supports. An adaptation of Strong Electrostatic Adsorption (co-SEA) to bimetallic nanoparticles was demonstrated over silica and alumina supports. With co-SEA, we demonstrate a relatively simple, effective, generalizable method to produce highly dispersed, well-alloyed bimetallic nanoparticles. Ten permutations of noble and base metals (platinum, palladium, copper, nickel, and cobalt) were synthesized with an average particle size of ~1nm on silica supports. Characterization through temperature-programmed reduction, X-ray diffraction, and electron microscopy confirmed the intimate and well-mixed atoms of the bimetallic pairs. Ultrasmall co-SEA Pt-Pd nanoparticles on alumina were evaluated as diesel oxidation catalysts (DOC) for the abatement of diesel exhaust emissions at Oak Ridge National Laboratory. These bimetallic alloyed Pt-Pd nanoparticles exhibited improved nanoparticle stability and phase alloying after hydrothermal treatments compared to conventionally synthesized Pt-Pd impregnation catalysts. Starting with smaller and more alloyed nanoparticles in the co-SEA catalyst resulted in higher catalyst dispersion and activity towards the oxidation of CO and hydrocarbons after simulated DOC lifetime.;Core-shell Ag-Ir catalysts were prepared by electroless deposition to demonstrate the principle of nanoparticle stabilization through differences in surface free energy (SFE). The combination of SEA and ED provided an unparalleled method to rationally control nanoparticle morphology. A low SFE Ag shell was deposited on the high SFE Ir cores. Not only was Ag anchored to Ir, but the addition of Ag improved the stability of the Ir nanoparticles up to 800°C. Experimental and computational studies revealed the addition of active sites for the Ag-Ir bimetallic pair compared to the monometallic Ir and Ag analogues. |
