XANES characterizations of amorphous mixed metal oxides derived from Zn/Al layered double hydroxides through thermal treatment

• Published in: Journal of solid state chemistry Vol. 316; p. 123567
• Main Authors: Shimamura, Akihiro, Jones, Mark I., Metson, James B.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.12.2022
• Subjects: Amorphous phase; Layered double hydroides; Thermal treatment; XANES; Zinc oxide; Zn L-edge spectra; Zn L-edge spectra; Zinc oxide; Layered double hydroides; XANES; Amorphous phase; Thermal treatment
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2022.123567

The amorphous phase obtained by thermal treatment of Zn/Al-layered double hydroxide (Zn/Al-LDH) was characterized by X-ray absorption near-edge Spectroscopy (XANES) and Ultraviolet–Visible Diffuse Reflection (UV–vis DR). The highly crystalline Zn/Al-LDH was synthesized through homogeneous precipitation with urea as precursor, and then calcined up to 900 ​°C. X-ray Diffraction (XRD) and Thermogravimetry-Differential Thermal Analysis (TG-DTA) results showed that the crystalline Zn/Al-LDH was changed to amorphous phase through dehydroxylation by 300 ​°C. The amorphous phase decomposed to wurtzite-ZnO and spinel (Zn/Al2O4) above 600 ​°C. The amorphous phase was characterized with Zn L-edge, O K-edge and Al K-edge spectra. Those spectra determined the formation of amorphous Zinc/Aluminium mixed metal oxide (ZAO) with characteristic electron. The ZAO showed absorption of UV light which is higher energy band gap than pure zinc oxide. The analysis indicated changes in coordination due to the formation of a metal oxide phase by dehydration of the hydroxide layer of Zn/Al-LDH, and the formation of ZAO. This research is believed to be the first to apply Zn L-edge, along with O K-edge XANES spectra to analyses and clarify the thermal behavior of Zn/Al-LDH and is demonstrated to be a powerful tool for probing the structure of a variety of mixed metal oxides and catalysts based on Zn based LDH materials. Amorphous metal oxide derived from Zn/Al-LDH was characterized by X-ray absorption near-edge Spectroscopy with Zn L-edge and Al K-edge. [Display omitted] •Directly observation of formation of an amorphous mixed oxide derived from a Zn/Al-LDH through thermal transition by XANES.•XANES spectra providing characteristic features of the chemical bonding due to the formation of the amorphous mixed oxide.•Optical property measurements showing existence of amorphous mixed oxide over temperature range between 300 ​°C and 400 ​°C.