(XRD) patterns were recorded using a D8 ADVANCE X-ray diffractometer
with Cu Kα radiation (λ = 0.15406 nm). The
scanning electron microscopy (SEM) images were recorded on an FEI-Sirion
200F field emission scanning electron microscope. The transmission
electron microscopy (TEM) images, high-resolution transmission electron
microscopy (HRTEM) images, selected area electron diffraction (SAED)
patterns, and the energy dispersive spectroscopy (EDS) spectra were
taken with an FEI-Tecnai G2 field emission transmission electron microscope.
The samples were obtained by peeling off the NiAl-LDH film from the
substrate. The Fourier transform infrared (FTIR) spectra were recorded
by a Thermo Nicolet 5700. The chemical state of LDHs was investigated
by X-ray photoelectron spectroscopy (XPS) on an ESCALAB 250Xi photoelectron
spectrometer with Al K (1486 eV) as the excitation light source. The
contents of metal ions in the solution were analyzed by an atomic
absorption spectrophotometer (TAS-990AFG). The UV–Vis diffuse
reflectance spectra were recorded by a UV–Vis spectrophotometer
(UV-3900H, Hitachi).