Enhancement of catalytic activity in NH3-SCR reaction by promoting dispersibility of CuCe/TiO2-ZrO2 with ultrasonic treatment

•Ultrasonic cavitation effect promotes the dispersibility of the catalysts.•Ultrasonic treatment enhances the synergistic interaction between Cu and Ce.•Ultrasound induces a higher ratio of Cu2+ and Ce3+ for better redox properties.•A novel qualitative analysis for active sites on catalysts by multifractal theory. A series of CuCe-modified TiO2-ZrO2 catalysts synthesized by stepwise impregnation method and ultrasonic-assisted impregnation method were investigated to research the removal of NO in the simulated flue gas. Results showed that the CuCe/TiO2-ZrO2 catalyst prepared by ultrasonic-assisted impregnation method exhibited the superior NO conversion, in which higher than 85% NO was degraded at the temperature range of 250–400 °C and the highest NO conversion of 94% at 350 °C. It proves that ultrasonic treatment can markedly improve the performance of catalysts. The effect of ultrasonic enhancement on CuCe/TiO2-ZrO2 was comprehensively studied through being characterized by physicochemical characterization. Results reveal that the ultrasonic cavitation effect improves the distribution of active species and the synergistic interaction between Cu with Ce components (Cu+ + Ce4+ ↔ Cu2+ + Ce3+) on the catalysts significantly, thus resulting in better dispersibility as well as a higher ratio of Cu2+ and Ce3+ of the catalysts. Moreover, it was found that the CuCe/TiO2-ZrO2 catalyst prepared by the ultrasonic-assisted impregnation method represented a higher degree of ultrafine metal particles and evenness. The above results were described with the generalized dimension and singularity spectra in multifractal analysis and validated by the comparative test. Therefore, it can be concluded that ultrasonic treatment facilitates the particle size and distribution of active sites on the catalysts.