Invia reflex confocal raman spectrometer

Raman spectra were recorded on an inVia-Reflex confocal Raman spectrometer (Renishaw, China) fitted with a 532 nm laser for excitation.

The morphology of the samples was characterized via SIGMA microscope (Zeiss, Germany) and transmission electron microscope (TEM, 2100F, JEOL). The crystal structures were explored by X-ray diffractometer (XRD-6100 spectrometer with Cu-Kα radiation, Shimadzu) and Raman spectrometer (inVia-reflex confocal Raman spectrometer, Renishaw) with a 532 nm laser as the excitation source. XPS spectra were obtained on a K-Alpha ESCALAB 250Xi instrument (ThermoFisher-VG Scientific, USA), with Al Kα radiation as the excitation source. N₂ adsorption–desorption analysis was measured on surface area and porosity analyzer (ASAP 2020, Micromeritics). BET method and the Barrett–Joyner–Halenda (BJH) method were performed to deduce the specific surface area and pore size distribution.