The oxygen release and storage properties of 1 wt% Pd-loaded Pr2O2SO4 were studied using different cycled feed stream methods, namely a flow microbalance, in situ X-ray diffraction and anaerobic CO oxidation in a flow reactor. The redox between Pr2O2SO4 and Pr2O2S exhibited a large oxygen storage of 2 (mol of O-2) mol(-1) at high temperatures. Loading Pd can activate reducing gases (H-2/CO) so as to promote the oxygen release by the reduction of bulk Pr2O2SO4 to Pr2O2S. In contrast, the oxygen storage by the reoxidation of Pr2O2S to Pr2O2SO4 was much faster even in the absence of Pd, because the redox between Pr3+ and Pr4+ on the solid surface plays the role of a mediator. Pd species also formed active catalytic sites for an anaerobic CO oxidation, which consumed lattice oxygens released from Pr202SO4. The full capacity oxygen storage of 2 (mol of O-2) mol(-1) and anaerobic oxidation of 4 (mol of CO) mol(-1) could be cycled. The CO/O-2 cycled feed stream reactions achieved CO conversion > 85% at 700 degrees C, almost comparable to that of a steady-state CO-O-2 reaction. The catalytic activity was not affected by the presence of SO2, which rather improved the stability of Pr2O2SO4/Pr2O2S. (C) 2007 Elsevier Inc. All rights reserved.