Structural analysis and characterization of layer perovskite oxynitrides made from Dion–Jacobson oxide precursors
✍ Scribed by Joshua A. Schottenfeld; Alan J. Benesi; Peter W. Stephens; Gugang Chen; Peter C. Eklund; Thomas E. Mallouk
- Book ID
- 104029269
- Publisher
- Elsevier Science
- Year
- 2005
- Tongue
- English
- Weight
- 537 KB
- Volume
- 178
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
A three-layer oxynitride Ruddlesden-Popper phase Rb 1+x Ca 2 Nb 3 O 10Àx N x Á yH 2 O (x ¼ 0:720:8, y ¼ 0:420:6) was synthesized by ammonialysis at 800 1C from the Dion-Jacobson phase RbCa 2 Nb 3 O 10 in the presence of Rb 2 CO 3 . Incorporation of nitrogen into the layer perovskite structure was confirmed by XPS, combustion analysis, and MAS NMR. The water content was determined by thermal gravimetric analysis and the rubidium content by ICP-MS. A similar layered perovskite interconversion occurred in the two-layer Dion-Jacobson oxide RbLaNb 2 O 7 to yield Rb 1+x LaNb 2 O 7Àx N x Á yH 2 O (x ¼ 0:720:8, y ¼ 0:521:0). Both compounds were air-and moisture-sensitive, with rapid loss of nitrogen by oxidation and hydrolysis reactions. The structure of the three-layer oxynitride Rb 1.7 Ca 2 Nb 3 O 9.3 N 0.7 Á 0.5H 2 O was solved in space group P4/mmm with a ¼ 3:887ð3Þ and c ¼ 18:65ð1Þ ( A, by Rietveld refinement of X-ray powder diffraction data. The two-layer oxynitride structure Rb 1.8 LaNb 2 O 6.3 N 0.7 Á 1.0H 2 O was also determined in space group P4/mmm with a ¼ 3:934ð2Þ and c ¼ 14:697ð2Þ (
A. GSAS refinement of synchrotron X-ray powder diffraction data showed that the water molecules were intercalated between a double layer of Rb+ ions in both the two-and three-layer Ruddlesden-Popper structures. Optical band gaps were measured by diffuse reflectance UV-vis for both materials. An indirect band gap of 2.51 eV and a direct band gap of 2.99 eV were found for the three-layer compound, while an indirect band gap of 2.29 eV and a direct band gap of 2.84 eV were measured for the two-layer compound. Photocatalytic activity tests of the three-layer compound under 380 nm pass filtered light with AgNO 3 as a sacrificial electron acceptor gave a quantum yield of 0.025% for oxygen evolution.