Effect of fluorine additive on CeO₂(ZrO₂)/TiO₂ for selective catalytic reduction of NO by NH₃

A series of CeO₂(ZrO₂)/TiO₂ catalysts with fluorine additive were prepared by impregnation method and tested for selective catalytic reduction (SCR) of NO by NH₃. These samples were characterized by XRD, N₂-BET, Raman spectra, SEM, TEM, NH₃-TPD, H₂-TPR and XPS, respectively. Results showed that the optimal catalyst with the appropriate HF exhibited excellent performance for NH₃-SCR and more than 96% NO conversion at 360 °C under GHSV of 71,400 h⁻¹. It was found that the grain size of TiO₂ increased and the specific surface area reduced with the modulation of HF, which was not good for the adsorption of gas molecule. However, the modulation of HF exposed the high energy (0 0 1) facets of TiO₂ and increased the surface chemisorbed oxygen concentration, oxygen storage capacity and Ce³⁺ concentration of catalyst. In addition, the synergy of (1 0 1) and (0 0 1) facets was beneficial to the improvement of catalytic activity.