Abatement of Nitrogen Oxides via Selective Catalytic Reduction over Ce1-W1 Atom-Pair Sites.

Abstract

Environmentally benign CeO2-WO3/TiO2 catalysts are promising alternatives to commercial toxic V2O5-WO3/TiO2 for controlling NOx emission via selective catalytic reduction (SCR), but the insufficient catalytic activity of CeO2-WO3/TiO2 catalysts is one of the obstacles in their applications because of a lack of an in-depth understanding of the CeO2-WO3 interactions. Herein, we design a Ce1-W1/TiO2 model catalyst by anchoring Ce1-W1 atom pairs on anatase TiO2(001) to investigate the synergy between Ce and W in SCR. A series of characterizations combined with density functional theory calculations and in situ diffuse-reflectance infrared Fourier-transform experiments reveal that there exists a strong electronic interaction within Ce1-W1 atom pairs, leading to a much better SCR performance of Ce1-W1/TiO2 compared with that of Ce1/TiO2 and W1/TiO2. The Ce1-W1 synergy not only shifts down the lowest unoccupied states of Ce1 near the Fermi level, thus enhancing the abilities in adsorbing and oxidizing NH3 but also makes the frontier orbital electrons of W1 delocalized, thus accelerating the activation of O2. The deep insight of the Ce-W synergy may assist in the design and development of efficient catalysts with an SCR activity as high as or even higher than V2O5-WO3/TiO2.