CATALYTIC-OXIDATION OF CO ON PT(335) - A STUDY OF THE ACTIVE-SITE

The catalytic reaction CO(a)+O(a)-->CO2(g) has been studied on Pt(335) using infrared reflection absorption spectroscopy (IRAS) and temperature programmed reaction (TPR) methods. Both dissociative 02 adsorption and CO adsorption occur preferentially on the step sites. It has been found that chemisorbed CO on the (111) terrace sites is more reactive than chemisorbed CO on the (100) step sites. In contrast, chemisorbed 0 on the step sites is more reactive at high CO coverages than chemisorbed 0 on the terrace sites. The results indicate that at high CO coverages the most reactive geometry involves step site O[O(S)] interacting with terrace sites CO [CO(T)]. This new information provides a conceptual basis for understanding the interplay between geometrical and energetic factors influencing the CO oxidation reaction.