• Ce–MnO 2 prepared by a mechanochemical method has excellent NOx–toluene removal. • Mechanochemical effect reduces oxygen vacancy formation energy of Ce–MnO 2 . • NH 3 and toluene compete for active sites to reduce Ce–MnO 2 activity at low temperature. • NO 2 can promote toluene oxidation on the Ce–MnO 2 surface at high temperature. The flue gas emitted from industrial processes, which contains nitrogen oxides (NO x ) and volatile organic compounds (VOCs), poses significant environmental challenges. The development of low-temperature catalysts with the simultaneous removal of NO x and VOCs through selective catalytic reduction (SCR) remains a key challenge. In this study, to achieve efficient synergistic removal of NO x and toluene (SR), a mechanochemical method was proposed for the preparation of a Ce-MnO 2 catalyst. Compared with other methods, the catalyst prepared by the mechanochemical method has more oxygen vacancies, surface active sites, and a higher proportion of Ce 3+ and O ads . These structural advantages result in the excellent removal efficiency for both individual and synergistic NO x and VOCs. Specifically, the catalyst exhibits the widest high-efficiency (above 90% conversion) SCR reaction temperature window, the lowest T 90 of toluene removal (T 90 is the temperature when the conversion of toluene reaches 90%) and reaction activation energy, and the synergistic removal conversions of NO x and toluene are more than 90% at 185–240 °C. The density functional theory (DFT) reveals that the two reactants (toluene and NH 3 ) are competitively adsorbed on the surface of the Ce-MnO 2 catalyst, which decreases the synergistic removal efficiency of NO x and toluene. However, at elevated temperatures, the by-products such as NO 2 can promote the redox of toluene and reduce the T 90 of toluene removal. These findings demonstrate that the mechanochemical method is not only a simple and rapid approach for preparing catalysts, but also successfully prepares the Ce-MnO 2 catalyst with superior bifunctional performance for NO x and toluene abatement, which provides a promising method for the development of advanced catalysts with synergistic removal pollutants.
Zhang et al. (Sun,) studied this question.