3.2 SEM and TEM analysis
The morphology and microstructure of MCS, NiSe2 and MCNS-10 samples were investigated by SEM and high-resolution TEM. As shown in Fig. 2a , the prepared MCS solid solutions were irregular particles and agglomeration agglomeration, which was consistent with the morphologies reported in previous literature [33]. In Fig. 2b , the NiSe2 was obviously observed to be greater irregular crystals than that MCS, some of them were cubic crystal structures consistent with XRD pattern. The TEM image (Fig. 2c ) showed some MCS nanoparticles were anchored on the surface of cubic NiSe2. Compared with pure MCS, the dispersion of MCS has been greatly improved in the composite catalyst, this intimate interface contact was conductive to separation and transfer of electron-hole pairs. HRTEM image in Fig. 2d shown the lattice fringes of the MCNS-10, the crystal plane spacing of 0.357 nm (red mark) and 0.298 nm (blue mark) were respectively corresponded to the (100) plane of hexagonal MCS and (200) plane of cubic NiSe2. Fig. 2e shown the EDX spectrum of the MCNS-10 which demonstrated the existence of Mn, Cd, S, Ni and Se elements, so the successful preparation of MCNS-10 may be proved. Further, the Cu element in the spectrum was mainly derived from the Cu carriers [34].