2.3. Characterizations
An X-ray diffractometer (D8 ADVANCE) from Bruker (Germany) was used to
perform powder X-ray diffraction (PXRD) throughout the 2 range of 5-40°
with a scan speed of 5° min−1 and a step size of
0.02°. The Brunauer-Emmett-Teller (BET) surface area and pore volume of
material were determined with a gas adsorption analyzer (Best, China).
Fourier transform infrared (FT-IR) was carried out with a Thermo
Scientific Nicolet iS5 spectrophotometer. The spectra data were measured
from 4000 to 400 cm-1. For the analysis of solid
samples, the samples were mixed with pure potassium bromide (KBr) and
sample (about 1:100 mass ratio), the sample powder was compressed into
flakes with a tablet machine, and then tested in an infrared instrument.
Pure ILs samples were firstly pressed to be tablets with dry pure
potassium bromide, then applied on potassium bromide by a small amount
of IL and put on the instrument for testing. The morphologies of samples
were investigated with scanning electron microscopy (SEM, Gemini SEM
300). Energy dispersive spectroscopy (EDS) elemental mapping images were
performed. Transmission electron microscope (TEM) images were measured
by a Japan-JEOL-JEM 2011Plus. X-ray photoelectron spectroscopy (XPS) was
attained on a Thermo Scientific K-Alpha with Al Kα radiation.
Thermogravimetric analysis (TGA) data were recorded using
Japan-Hitachi-TG DTA7200. Instrument under N2 atmosphere
with a heating rate of 10 K·min-1 from 298 K to 783 K.