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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 5, Number 4
April 20, 1984 

An X-ray Diffraction Study of Na, Ag-A Reduced by Hydrogen. Ag3+ and Ag32+ Clusters
Yang Kim, Karl Seff
The reduction of vacuum-dehydrated NaxAg12-x-A, 0 ≤ x ≤ 9.2, and its reoxidation by O2, have been studied by X-ray powder diffraction. Also, the structure of Na6Na6-A treated with hydrogen at room temperature has been studied by single crystal methods in the cubic space group Pm3m at 24℃ (a = 12.221(2) Å). The diffraction pattern of dehydrated Ag12-A reduced by H2 contains only the (111) and (200) reflections of silver metal, indicationg that the zeolite structure has been lost, but the zeolite's diffraction pattern and structural integrity can be fully restored by oxidation with O2 at 100 or 200℃. In contrast, the structures of NaxAg12-x-A, x = 4.5 and 9.2, were not destroyed by treatment with hydrogen. Dehydrated Na6Ag6-A treated with 50 Torr of hydrogen gas at 24℃ for 30 minutes has 6 Na+ and 1.27 Ag+ ions at 6-ring sites. These Ag+ ions are associated with 2.54 Ag°atoms to form 1.27 Ag3+ clusters per unit cell. Also found were 0.7 Ag32+ clusters per unit cell near the 8-rings. The structure was refined to the final error indices R1 = 0.134 and R2 (weighted) = 0.147, using 168 independent reflections for which I0 > 3σ(I0).
135 - 140
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