F2100

Scanning electron microscopy (SEM) micrograph and elemental mapping analysis were obtained using a field-emission scanning electron microscope (Hitachi S-4800). Transmission electron microscopy (TEM) micrograph was recorded with a transmission electron microscope (JEOL F2100). The porosity was measured by the mercury intrusion method (AutoPore IV 9510, Micromeritics). Thermogravimetric analysis (TGA) was carried out using a thermal analyzer (STA 409/PC, Netzsch) in flowing air at a heating rate of 10 °C min⁻¹. The Brunauer–Emmett–Teller (BET) specific surface area was measured using a surface area analyzer (Tristar II 3020, Micromeritics). Fourier transform infrared (FTIR) spectroscopy was recorded with a FTIR spectrometer (Thermo Nicolet Nexus 470). X-ray powder diffraction (XRD) pattern was recorded using an X-ray diffractometer (Rigaku D/max 2550 V, Cu Kα radiation, λ = 1.54178 Å). The pore size distribution curve was analysed using a pore size analyzer (3H-2000, Beshide Instrument Technology) based on a bubble point method. The zeta potential was measured by a potential analyzer (ZetaPlus, Brookhaven, USA).