Abatement of Nitrogen Oxides via Selective Catalytic Reduction over Ce 1 -W 1 Atom-Pair Sites.

Environmentally benign CeO 2 -WO 3 /TiO 2 catalysts are promising alternatives to commercial toxic V 2 O 5 -WO 3 /TiO 2 for controlling NO x emission via selective catalytic reduction (SCR), but the insufficient catalytic activity of CeO 2 -WO 3 /TiO 2 catalysts is one of the obstacles in their applications because of a lack of an in-depth understanding of the CeO 2 -WO 3 interactions. Herein, we design a Ce 1 -W 1 /TiO 2 model catalyst by anchoring Ce 1 -W 1 atom pairs on anatase TiO 2 (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 Ce 1 -W 1 atom pairs, leading to a much better SCR performance of Ce 1 -W 1 /TiO 2 compared with that of Ce 1 /TiO 2 and W 1 /TiO 2 . The Ce 1 -W 1 synergy not only shifts down the lowest unoccupied states of Ce 1 near the Fermi level, thus enhancing the abilities in adsorbing and oxidizing NH 3 but also makes the frontier orbital electrons of W 1 delocalized, thus accelerating the activation of O 2 . 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 V 2 O 5 -WO 3 /TiO 2 .