Oxygen surface exchange kinetics on PrBaCo2O5 + δ

The surface oxygen exchange kinetics on the double perovskite PrBaCo2O5 + δ has been studied using pulse 18O–16O isotope exchange measurements in the temperature range from 300 to 500 °C. The exchange rate, at oxygen partial pressure of 0.21 atm, shows an activation energy of 97 ± 3 kJ mol− 1. A two-step exchange mechanism is applied to account for the observed distribution of 16O2, 16O18O, and 18O2 in the effluent pulses. The results indicate that the oxygen exchange kinetics on PrBaCo2O5 + δ is determined by the rates of homolytic oxygen dissociative adsorption on the PrBaCo2O5 + δ surface and incorporation of oxygen adatoms in the oxide lattice. A changeover of the rate-determining step occurs upon increasing pO2 from 0.1 to 0.95 atm.