UV Raman Studies of Adsorbed Oxygen and NO sub(x) Species on Pt/ gamma -Alumina Catalysts

Scientists derived in situ Raman spectra at 244 nm from a variety of Pt/ gamma -Al sub(2)O sub(3) catalysts under gas flows containing O sub(2), CO, NO sub(2), and H sub(2) at temperatures in the range of 20-600 degree C. Researchers observed a broad peak at 571/cm with O sub(2) or NO sub(2). This finding was attributed to the Pt-O stretch model of atomic oxygen. Data from this study are considered the first direct spectroscopic observation of this fundamental species on a real catalyst. Both CO and H sub(2) proved capable of removing the peak, even in tests enacted at room temperature. The appearance of several peaks linked to surface NO sub(x) species with NO sub(2) exposure is reviewed. Issues that should be addressed in future in situ analyses of catalytic mechanisms are discussed.