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

Environmentally benign CeO-WO/TiO catalysts are promising alternatives to commercial toxic VO-WO/TiO for controlling NO emission via selective catalytic reduction (SCR), but the insufficient catalytic activity of CeO-WO/TiO catalysts is one of the obstacles in their applications because of a lack of an in-depth understanding of the CeO-WO interactions. Herein, we design a Ce-W/TiO model catalyst by anchoring Ce-W atom pairs on anatase TiO(001) to investigate the synergy between Ce and W in SCR. A series of characterizations combined with density functional theory calculations and diffuse-reflectance infrared Fourier-transform experiments reveal that there exists a strong electronic interaction within Ce-W atom pairs, leading to a much better SCR performance of Ce-W/TiO compared with that of Ce/TiO and W/TiO. The Ce-W synergy not only shifts down the lowest unoccupied states of Ce near the Fermi level, thus enhancing the abilities in adsorbing and oxidizing NH but also makes the frontier orbital electrons of W delocalized, thus accelerating the activation of O. 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 VO-WO/TiO.