A series of CuMnCeO catalysts with 10% CuO (weight loading) and variable atomic ratios of Mn/Mn + Ce (0, 0.02, 0.05 or 0.10) were synthesized by co-precipitation and employed for CO preferential oxidation (CO PROX). After doping a small amount of manganese into ceria, the catalysts show improved catalytic performance as compared with the undoped one, especially the catalyst with the Mn/Mn + Ce atomic ratio of 0.05 (CMC-0.05) which displays the lowest temperatures for half CO conversion (T-50 = 73 degrees C) and full CO conversion (T-100 = 108 degrees C). In addition, it also exhibits the widest temperature window of full CO conversion (108-149 degrees C) and 100% selectivity of oxygen to CO2 below 117 degrees C. As revealed by XRD and UV-Raman, the presence of appropriate amount of Mn cannot only enhance the formation of Ce-Cu-Mn-O ternary oxide solid solution with fluorite structure, inhibiting the growth of CeO2 crystallite size, but also increase the oxygen vacancies. The results of H-2-TPR and XPS indicate that the reducibility and amount of surface oxygen species of CMC-0.05 are also improved, both of which are beneficial to catalytic performance. In situ XANES results suggest that the bulk copper species still remain as Cu2+ ions below 200 degrees C even in H-2-rich CO PROX atmosphere; however, the in-situ DRIFTS spectra indicate that during CO PROX below 120 degrees C the surface copper species are Cu+ ions which are regarded as the main active sites for CO PROX; above 120 degrees C Cu-0 species appear, which enhance H-2 oxidation, decreasing the oxygen to CO2 selectivity. Copyright (C) 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.