Escalab mk 2

All chemicals and solvents were supplied from Fluka (Switzerland) or Merck (Germany). We used an ESCALab MKII (Thermo Fisher Scientific, USA) spectrometer with Al Kα (1.4866 keV) as the X-ray source to determine X-ray photoelectron spectroscopy (XPS). The ¹H NMR and ¹³CNMR analyses were carried out with a BRUKER DRX-250 AVANCE spectrometer at 250.0 MHz. The optical emission spectrometer inductively coupled plasma (Varian Vista MPX ICP-OES Axial) was used to measure content of W in the catalysts. X-ray diffraction (XRD) spectra were obtained on a Siefert XRD 3003 PTS diffractometer with Cu Kα radiation (λ = 1.54 Å). Thermogravimetric analysis (TGA) was recorded using a TGA Q 50 analyzer under N₂ flow at a heating rate of 10 °C min⁻¹. The optical characteristics of samples were measured by Shimadzu UV 2100 151PC UV–Visible spectrophotometer at room temperature. Field emission scanning electron microscope (FE-SEM) imaging and energy-dispersive X-ray spectroscopy (EDX) analysis were carried out on a SIGMA VP 500 (Zeiss) microscope equipped with an EDX measurement system. A Philips EM10C 200 kV microscope was used to record transmission electron microscopy (TEM) images. The fourier-transform infrared spectroscopy (FT-IR) spectra of the samples were recorded with the KBr pellet method by PerkinElmer PE-1600-FTIR spectrometer.

A field emission scanning electron microscope (FESEM, JSM-7600F, JEOL, Tokyo, Japan) was used for the evaluation of FPCs’ samples’ morphology. The transmission electron microscope (TEM, JEM-2100UHR, JEOL, Tokyo, Japan) was used to characterize the microstructures of the FPCs. To investigate the proportion of FPCs, a thermogravimetric analysis (TGA, TGA/SDTA851, Mettler Toledo, Zurich, Switzerland) was carried out from room temperature to 700 °C at a rate of 10 °C/min under air flow. An X-ray diffractometer (XRD, PANalytical X’Pert Pro, Panalytical, Almelo, The Netherlands) was used to analyze the crystal structures of FPCs, and an X-ray photoelectron spectroscopy (XPS, ESCALAB MK II, Thermo Scientific, Waltham, MA, USA) analysis was conducted to detect the surface chemical state of the samples. The specific surface areas (S_BET) and pore size distributions were calculated from the N₂ adsorption-desorption isotherms obtained on the automatic analyzer at 77 K (Micromeritics ASAP 2020, Micromeritics, Norcross, GA, USA).