NH3-DeNO(x) performances of the combined catalysts (CombiCats) prepared by mechanical mixing of RedOx component (CeO2-ZrO2 or Mn-Ce/CeO2-ZrO2) and zeolite component (Fe-Beta, H-Beta, USY, etc.) were studied in details. By comparing DeNO(x) performances of the CombiCats and their individual components a pronounced synergistic effect was revealed, as evidenced by the improvement of DeNO(x) activities and selectivities far above performances of the individual components. Significant improvement was observed within 150-250 degrees C temperature range. Detailed study of a possible origin of the synergistic effect suggested that the improvement of NH3-DeNO(x) activity can be attributed to the bifunctional mechanism comprising two main stages: 2NO + O-2 <-> 2NO(2) over RedOx component (1) NO + NO2 + 2NH(3) -> 2N(2) + 3H(2)O over zeolite component (2) Remarkably, the synergistic effect was attained by mixing RedOx component with H-Beta possessing negligible activity in Standard SCR but active in Fast SCR. Nevertheless, further research is required for revealing overall reaction network and understanding reaction mechanism responsible for the observed synergy. (C) 2015 Elsevier B.V. All rights reserved.