Maximising the oxygen storage capacity (OSC) or oxygen uptake of CeO2 based materials is a primary driving force in their development for use as catalysts, gas sensors and air separation materials. Higher oxygen uptakes can be achieved by aliovalent doping with Pr3+/Pr4+ to generate oxygen vacancy defects. The oxygen uptake of a series of Pr-CeO2 materials was measured using thermogravimetric analysis (TGA) at 420 °C and 600 °C and at both temperatures the 20 % Pr-CeO2 was found to have the highest uptake. Addition of Cu to Pr-CeO2 further increased the uptake although scanning electron microscopy energy-dispersive X-ray spectroscopy (SEM-EDS) revealed evidence of a segregated phase rich in Cu. Electron energy loss spectroscopy (EELS) was used to investigate the effect of Pr addition to CeO2; the Ce M5/M4 and O IB/IC ratios were calculated as these can be used to indicate changes in the Ce3+ and vacancy concentration, respectively. As the exhibited uptakes of Pr containing materials can be attributed to their reducibility, the stability of Pr-CeO2 was evaluated via monitoring the change in Ce M5/M4 and O IB/IC as a function of time. After prolonged irradiation the O fine structure features broadened and changes in the peak intensities due to reduction were observed. Thus, the oxygen uptake of Pr-CeO2 can be attributed to the presence of vacancies and cations in the +3 oxidation state which act as absorption sites.