Platinum nanoparticle cubes in a catalytic flow reactor investigated by SFG vibrational spectroscopy

A model catalytic system composed of a monolayer of polymer capped 7 nm platinum cubes deposited on an α-alumina surface was studied by in situ total internal reflection sum frequency generation vibrational spectroscopy. SFG was employed to characterize nanoparticles during oxidation/reduction cycles, and in the presence of ethylene and CO. Subsequent to cleaning, the SFG spectrum of ethylene corresponded well with published data on a platinum(100) single crystal. In the presence of CO, the surface species restructure and linearly bound CO was observed. CO intensity and frequency was sensitive to the state of the nanoparticle and available sites. Rates were measured in flowing oxygen during the catalytic oxidation of CO. The apparent activation energy for CO oxidation was measured by the decay of the CO SFG intensity. In total internal reflection geometry, the sensitivity was increased with extremely low incident laser power and the effect of destructive interference was minimized. This is an abstract of a paper presented at the 231st ACS National Meeting (Atlanta, GA 3/26-30/2006).