Mechanistic insights into sequential impregnation for inducing active sites evolution in Fe-Mo-W/TiO2 catalysts: A multiscale study.

This study investigates the mechanistic effects of sequential impregnation on Fe-Mo-W/TiO2 catalysts for synergistic removal of NOx and VOCs from coal-fired flue gas. Through experimental characterization, molecular dynamics simulations, and density functional theory calculations, we demonstrate that the impregnation sequence critically governs catalytic performance. Catalysts with Mo-prioritized impregnation or Fe+W co-impregnation exhibited superior activity: NOx conversion consistently outperformed the control group within 260-420°C, reaching a maximum of 94.8 %, while maintaining excellent VOCs removal efficiency exceeding 94.4 % for benzene and 82.5 % for toluene. Characterization revealed that Mo-prioritized impregnation reduced the surface PZC, facilitating crystalline Fe2O3 formation and stabilizing high-valence Fe3 + . Molecular dynamics simulations showed Fe+W co-impregnation mitigated metal clustering, whereas Fe-first sequences promoted detrimental Fe-Mo compounds. Density functional theory calculations identified site-specific adsorption behaviors, with Mo sites dominating NO/O2 chemisorption and Fe sites preferentially activating NH3. This work establishes a theoretical framework for designing bimetallic catalysts through impregnation sequence optimization.