Structural Investigation of Zn(II) Insertion in Bayerite, an Aluminum Hydroxide.
Bayerite was treated under hydrothermal conditions (120, 130, 140, and 150 °C) to prepare a series of layered double hydroxides (LDHs) with an ideal composition of ZnAl4(OH)12(SO4)0.5·nH2O (ZnAl4-LDHs). These products were investigated by both bulk techniques (powder X-ray diffraction (PXRD), transmission electron microscopy, and elemental analysis) and atomic-level techniques ((1)H and (27)Al solid-state NMR, IR, and Raman spectroscopy) to gain a detailed insight into the structure of ZnAl4-LDHs and sample composition. Four structural models (one stoichiometric and three different defect models) were investigated by Rietveld refinement of the PXRD data. These were assessed using the information obtained from other characterization techniques, which favored the ideal (nondefect) structural model for ZnAl4-LDH, as, for example, (27)Al magic-angle spinning NMR showed that excess Al was present as amorphous bayerite (Al(OH)3) and pseudoboehmite (AlOOH). Moreover, no evidence of cation mixing, that is, partial substitution of Zn(II) onto any of four Al sites, was observed. Altogether this study highlights the challenges involved to synthesize pure ZnAl4-LDHs and the necessity to use complementary techniques such as PXRD, elemental analysis, and solid-state NMR for the characterization of the local and extended structure of ZnAl4-LDHs.
Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark.
Suraj Shiv Charan
SS
Pushparaj
Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark.
Nicholai Daugaard
ND
Jensen
Institut de Chimie de Clermont-Ferrand, Université Clermont Auvergne, Université Blaise Pascal , BP 10448, F-63000 Clermont-Ferrand, France.|CNRS, UMR 6296 , F-63178 Aubiere, France.
Claude
C
Forano
Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL, U.K.
Gregory J
GJ
Rees
Institut de Chimie de Clermont-Ferrand, Université Clermont Auvergne, Université Blaise Pascal , BP 10448, F-63000 Clermont-Ferrand, France.|CNRS, UMR 6296 , F-63178 Aubiere, France.
Vanessa
V
Prevot
Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL, U.K.
John V
JV
Hanna
Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark.
Dorthe B
DB
Ravnsbæk
Department of Chemistry and Interdisciplinary Nanoscience Center, Aarhus University , Gustav Wiedsvej 14, 8000 Aarhus C, Denmark.
Morten
M
Bjerring
Department of Physics, Chemistry, and Pharmacy, University of Southern Denmark , Campusvej 55, 5230 Odense M, Denmark.
Ulla Gro
UG
Nielsen