Energy dependent transient reaction kinetics of CO oxidation on Pd{1 1 0}

Translational energy dependence of CO adsorption and CO oxidation have been investigated by performing molecular beam surface scattering experiments on Pd{1 1 0}. We find that CO adsorbs molecularly on clean and oxygen precovered Pd{1 1 0} over a range of surface temperatures (300–500 K) and translational energies (4.8–21 kJ/mol). The initial sticking probability (S0) of CO on clean Pd{1 1 0} is shown to be strongly energy dependent. Only a weak surface temperature dependence is observed. Evidence is provided for the CO adsorption process being weakly activated. S0 of CO on the Pd{1 1 0}c(2×4)–O surface is largely energy independent. The initial reaction probability is, however, determined to depend on the CO translational energy. Both the surface temperature and the translational energy of CO are shown to enhance the initial reaction rate and shorten the reaction induction time required for the CO2 formation rate to reach its maximum. The role of the CO translational energy is discussed in terms of the weakening of the Pd–O bond.