We introduced oxygen vacancies into Nb2O5 via thermal treatment at 700 degrees C under oxygen-deficient conditions for different lengths of time. Niobia-supported Pt catalysts were subsequently synthesized using the wet impregnation method with the fabricated Nb2O5. The catalytic activity of the synthesized catalysts for CO oxidation exhibited a significant increase from that obtained for a counterpart having the Nb2O5 support treated under saturated oxygen conditions (i.e., in air). Moreover, increasing the number of oxygen vacancies was found to increase the catalytic activity. At 150 degrees C, the TOF calculated for the catalyst with the most oxygen vacancies was 0.36 s(-1), which was much higher than that obtained from the catalyst possessing the fewest oxygen vacancies (0.05 s(-1)). Systematic characterization of the synthesized catalysts revealed the crucial impact of oxygen vacancies and active lattice oxygen on the enhancement of catalytic activity. (C) 2019 Elsevier Inc. All rights reserved.