The effect of Nb promotion over a Cu-CeO2 catalyst was investigated in the lowtemperature water gas shift reaction. The Nb loading amount was systematically varied from 0 to 5 wt% for the Cu-Nb-CeO2 catalyst, and the 1 wt% Nb promoted Cu-Nb-CeO2 catalyst exhibited the highest catalytic performance even at extremely high GHSV of 72,152 h(-1). The catalysts were characterized through various techniques such as BrunauerEmmet-Teller measurements, X-ray diffraction, N-2 O-chemisorption, H-2-temperature programmed reduction, X-ray photoelectron spectroscopy, and transmission electron microscopy. It was found that the superior performance of the 1 wt% Nb promoted Cu-Nb-CeO2 catalyst was due to its enhanced reducibility, high BET surface area, small metallic Cu crystallite size, and high number of oxygen vacancies. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd.