Oxygen surface exchange kinetics on PrBaCo2O5+δ

The surface oxygen exchange kinetics on the double perovskite PrBaCo2O5 + delta has been studied using pulse O-18-O-16 isotope exchange measurements in the temperature range from 300 to 500 degrees 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 O-16(2), (OO)-O-16-O-18, and O-18(2) in the effluent pulses. The results indicate that the oxygen exchange kinetics on PrBaCo2O5 + delta is determined by the rates of homolytic oxygen dissociative adsorption on the PrBaCo2O5 + delta surface and incorporation of oxygen adatoms in the oxide lattice. A changeover of the rate-determining step occurs upon increasing pO(2) from 0.1 to 0.95 atm. (C) 2013 Elsevier B.V. All rights reserved.