Tristar 2 3020 system

XRD analysis was performed using an X-ray diffractometer (Empyrean; PANalytical, Almelo, The Netherlands). The samples were scanned at 2θ from 0.5 to 2.5° using a step size of 0.0070° and a scanning time of 19.9260 s. Nitrogen adsorption and desorption isotherms were measured using a TriStar II 3020 system (Micromeritics, Norcross, GA, USA). The samples were analyzed at 77.35 K. The adsorption and desorption data were calculated using Brunauer–Emmett–Teller (BET) theory to determine the specific surface area of the samples, and the pore-size distributions and pore volumes were determined using the Barrett–Joyner–Halenda (BJH) theory. Infrared (IR) spectra were obtained using a NICOLET IS 10 spectrometer (Thermo Fisher Scientific, Waltham, MA, USA). Microscopic images of nanoscale pore structures were taken using a transmission electron microscope (HT 7700 TEM; Hitachi, Tokyo, Japan) at 120 kV.

The structure and morphology of prepared samples were investigated using scanning electron microscopy (SEM; S-4200 field-emission, Hitachi) and high resolution-transmission electron microscopy (HR-TEM; JEOL JEM-2010). Nitrogen adsorption–desorption analysis was conducted with 77 K with Micromeritics Tristar II 3020 system to estimate pore size and specific surface area. To confirm the specific pore morphology, small-angle X-ray scattering (SAXS) patterns was detected using 4C SAXS beamlines at the Pohang Light Source (PLS). To investigate crystalline phase, X-ray diffraction (XRD) pattern was identified by D/max-2500 a diffractometer (Rigaku, Cu-Kα radiation). The carbon content of m-TiO₂-C was estimated using thermogravimetric analysis (TGA; NETZSCH STA 449C). Electron energy loss spectroscopy (EELS) analysis was performed to identify containing elements using energy-filtering transmission electron microscopy (EF-TEM, JM-220FS).