*3.4. Characterization of SeCS*

The surface morphologies of the samples were detected using MIRA4 SEM (Tescan, Brno, Czech). The elemental compositions of the samples were measured using a MIRAL SEM-EDS (Tescan, Brno, Czech). The FT–IR spectrums of the samples were measured using a Tensor 27 spectrometer (Bruker, Karlsruhe, Germany) from 4000 to 400 cm−<sup>1</sup> with a 4 cm−<sup>1</sup> resolution, i.e., 2 mg of the sample was completely ground with the spectroscopic grade potassium bromide (KBr) powder and a transparent tablet was used for measurement. The X-ray diffractometer of the samples was obtained using an Ultima VI diffractometer (Rigaku, Tokyo, Japan) operated at 40 kV and 40 mA. Moreover, the samples were investigated in the range of 10–80 degree (2θ angle).
