Promotional role of Nb modification on CuCeOx catalyst for low temperature selective catalytic reduction of NO with NH3: A mechanism investigation

• Nb modification can promote the adsorption of reactants on CuCeO x catalyst. • The SCR reaction on CuCeNbO x -0.4 catalyst mainly follows the L-H and E-R mechanisms. • The formed dual redox cycle on CuCeNbO x -0.4 catalyst favors the low-temperature SCR reaction. CuCeO x and CuCeNbO x - k with different Nb doping ratios were obtained by the citric acid method and applied in NH 3 -SCR process. The activity test results elucidated that the addition of Nb effectively ameliorated the low-temperature SCR performance. Among them, CuCeNbO x -0.4 catalyst had the finest SCR activity (more than 90% in 185–370 °C), highest N 2 selectivity, excellent SO 2 &H 2 O resistance and thermal stability. Numerous characterization analysis demonstrated that CuCeNbO x -0.4 had the largest specific surface area, the strongest surface acidity and the most excellent redox properties. The conclusions of in situ DRIFT manifested the Nb modification generated more activated species, enhanced the reactivity of ad-NH 3 and ad-NO x species, and the SCR reaction on CuCeNbO x -0.4 mainly followed the Langmuir-Hinshelwood (L-H) and Eley-Rideal (E-R) mechanisms. Furthermore, the Nb doping also formed the dual redox cycle (Cu 2+ + Nb 4+ ↔ Cu + + Nb 5+ , Cu 2+ + Ce 3+ ↔ Cu + + Ce 4+ ), which facilitated the low-temperature SCR reaction.