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Uniform Generation of Sub-nanometer Silver Clusters in Zeolite Cages Exhibiting High Photocatalytic Activity under Visible Light

El-Roz, Mohamad, Telegeiev, Igor, Mordvinova, Natalia E., Lebedev, Oleg I., Barrier, Nicolas, Behilil, Asma, Zaarour, Moussa, Lakiss, Louwanda, Valtchev, Valentin
ACS applied materials & interfaces 2018 v.10 no.34 pp. 28702-28708
carbon dioxide, crystals, ethanol, formic acid, hydrogen, nanosilver, photocatalysis, silver, zeolites
Sub-nanometer silver clusters that exhibit discrete electronic structure with molecular-like properties are highly desirable in various technologies. However, the methods for their preparation suffer from limitations related with the reproducibility and particles uniformity and/or the possibility of the scale-up. Another critical drawback is that free sub-nanometer silver clusters tend to aggregate into larger particles. In this work, a new approach that successfully overcomes the above limitations is developed. It allows, for the first time, an ultrafast preparation of sub-nanometer silver particles with high abundance, uniformity (7 Å), and stability into the cages of nanosized zeolite crystals. The new method consists of UV excitation of a water suspension of nanozeolite containing photoactive vanadate clusters in the presence of ethanol (as an electron donor) and silver precursor. The characteristic features of sub-nanometer silver particles are presented, and the mechanism of their formation is discussed. Sub-nanometer Ag clusters exhibit exceptional photocatalytic activity and selectivity in the reforming of formic acid to H₂ and CO₂ under visible light.