Effects of Pd particle size on the rates of oxygen back-spillover and CO oxidation under dynamic oxygen storage and release measurements over Pd/CeO2 catalysts

Abstract

A kinetic mathematical model has been applied to investigate for the first time the effects of Pd particle size on the rates of oxygen back-spillover and CO oxidation during Oxygen Storage Capacity (OSC) measurements under dynamic conditions over Pd/CeO2 catalysts in the 500–700 °C range. The dependence of the intrinsic rate constant k1 of the CO oxidation reaction on PdO, and that of k 2 app of the oxygen back-spillover from ceria to Pd/PdO on the palladium particle size was estimated by performing curve-fitting of the experimental CO and CO2 pulse transient responses obtained. Activation energies of 8.0, 9.5 and 21.1 kJ/mol were calculated for the Eley–Rideal step of CO oxidation for the 1.3, 1.8 and 16.4 nm Pd particles, respectively, supported on CeO2. The transient rates of CO oxidation and oxygen back-spillover were found to decrease with increasing Pd particle size.