KINETICS OF CO OXIDATION ON SINGLE-CRYSTAL Pd, Pt, AND Ir.

Article abstract of DOI:10.1021/j100329a030

The activity of Pt(100), Pd(110), Ir(111), and Ir(110) single-crystal catalysts for CO oxidation has been studied as a function of temperature and partial pressure of O//2 and CO in a high-pressure reactor-ultra-high-vacuum surface analysis apparatus over the temperature range 425-725 K and pressure range 0. 1-600 Torr. The specific rates and the partial pressure dependencies determined for the single crystals are in excellent agreement with results obtained previously for high surface area supported catalysts, demonstrating the structure insensitivity of this reaction. The single-crystal catalysts exhibit simple Arrhenius behavior over most of the temperature range studied, and the observed activation energies lie between 22 and 33 kcal/mol, close to the desorption energy of CO from these surfaces. These results are consistent with the generally accepted model in which the surface is primarily covered with CO and the reaction rate is controlled by the desorption of CO.