CO ADSORPTION ON PD(111) AND PD(100) - LOW AND HIGH-PRESSURE CORRELATIONS

The adsorption of CO on Pd(111) and Pd(100) have been studied using infrared reflection-absorption spectroscopy over a wide range of CO pressures and temperatures. A strong dependence of CO adsorption on the initial conditions was found for Pd(111) while CO adsorption on Pd(100) was essentially independent of the conditions of adsorption. Initial isosteric heats of adsorption of 30 and 38 kcal/mol were determined for Pd(111) and Pd(100), respectively. For Pd(111) and equilibrium phase diagram was constructed on the basis of the infrared (IR) data. The excellent correspondence among IR data for the single crystal Pd surfaces and a supported Pd catalyst suggests that the Pd particles in the supported catalyst consist primarily of low index [(111) and (100)] crystal faces.