CO OXIDATION ON PALLADIUM .2. A COMBINED KINETIC-INFRARED REFLECTION-ABSORPTION SPECTROSCOPIC STUDY OF PD(111)

The oxidation of carbon monoxide was studied on a single-crystal Pd(11 1) catalyst using an elevated pressure IR cell/ultrahigh vacuum surfac e analysis system. The reaction kinetics were followed at elevated pre ssures by measuring the total pressure change during the course of rea ction. In the temperature range of 500-570 K an apparent activation en ergy of 28.1 +/- 0.3 kcal/mol was determined, which agrees well with t he 25 +/- 2 kcal/mol obtained for the heat of adsorption of CO on Pd(1 11). Below 500 K the apparent activation energy decreases to 21 kcal/m ol in concert with the decrease in the CO heat of adsorption.