UC Riverside

The surface structures of catalysts have in some instances a large impact on their catalytic properties. On the other hand, historically, mild reactions are not considered to be surface structure sensitive. In this thesis we report on our observation that both the size and the shape of Pt nanoparticles strongly affect the selectivity of glycerol oxidation, a reaction that can proceed at low temperature and under atmospheric pressures. In a series of experiment using Pt/SiO2 catalysts with average particle sizes varying from 3.9 to 5.7 nm, it was determined that selectivity toward primary carbon oxidation increases as the proportion of larger particles increases. Together with CO IR titration result, these results appears to indicate that larger Pt particles with flat surfaces and extensive fractions of atop and bridge sites may promote primary carbon oxidation, whereas edge, corner, and other low-coordination Pt sites may promote secondary carbon oxidation. Further catalyst characterization and kinetic experiments will be needed to confirm this tentative conclusion. Tetrahedral- and cuboctahedral-shaped Pt catalysts were also tested for the glycerol oxidation reaction, and cuboctahedral-shaped Pt nanoparticles were found to display higher activity and higher selectivity toward primary carbon oxidation.