*3.3. Catalyst Characterization*

The X-ray di ffraction (XRD) profiles of the catalysts were recorded using a Rigaku D/Max-RA di ffractometer (Tokyo, Japan) with Cu K α radiation operated at 40 kV. The specific surface areas of the catalysts were carried out on a Micromeritics ASAP-2000 instrument (Norcross, GE, USA). UV-visible spectroscopy was obtained on a Jasco V-550 spectrophotometer (Tokyo, Japan). Transmission electron microscope (TEM) images were conducted by a Tecnai G2 F20 S-Twin microscope operating (Hillsboro, OR, USA) at 200 kV. The morphology of the catalyst was investigated using a JEOL JSM-7001F scanning electron microscope (SEM). The total chemical compositions of the catalysts were determined using inductively coupled plasma-atomic emission spectroscopy (ICP-AES) with an Optima 2000 DV spectrometer (PerkinElmer, Waltham, MA, USA). X-ray photoelectron spectroscopy (XPS) was performed using a Thermo VGESCALAB250 X-ray photoelectron spectrometer (Waltham, MA, USA) with an Al K α source. All binding energies were referenced to the C 1s peak at 284.6 eV.
