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.