Niobia and alumina supported palladium catalyst promoted by copper were investigated in the reaction of nitrate catalytic reduction in water and characterized by temperature programmed reduction, physisorption, H-2 chemisorption and X-ray diffraction. Niobia supported Pd-Cu catalysts were as active and selective as an alumina supported catalyst. All catalysts had similar turnover frequencies independent of the support. The control of pH and the interaction between Pd and Cu were critical to improving the selectivity and activity of Pd-Cu/Nb2O5 catalysts. (c) 2007 Elsevier B.V. All rights reserved.