Unveiling the Mechanistic Origin of High Efficiency in Selective Reduction of NO by NH over Mn-W/CeO Catalysts: Sufficient Acidity and Appropriate Reducibility.

Achieving remarkable activity in selective catalytic reduction of NO by NH (NH-SCR) over CeO-based catalysts was crucial for their industrial application but still faces a tough challenge, mainly owing to the insufficient acidity and overoxidation ability. Herein, the surface acidity and reducibility of CeO catalysts were finely tuned over Mn-W/CeO to efficiently eliminate NO and reveal the mechanistic origin of superior catalytic properties. Systematic surface and structure analyses revealed that MnO interacted with WO species in the possible form of Mn-O-W, which could enhance the dispersion of WO over the CeO surface. The resulting well-dispersed WO increased the concentration of both Brønsted acid sites and strong acid sites, effectively suppressing the generation of inactive nitrates and thus providing abundant catalytically active sites for the adsorption and activation of NH. Importantly, the electron withdrawal from Mn by W atoms associated with the shortened Mn-O bond distance resulted in the appropriate reducibility over Mn-W/CeO. Accordingly, the undesirable overoxidation of NH was weakened, thereby greatly increasing the high-temperature (250-400 °C) NH-SCR activity. DFT calculations and detailed in situ DRIFTS analysis demonstrated that both "E-R" and "L-H" mechanisms contributed mainly to this superior performance.