3.5 BET surface areas and pore size distributions
The calculation results of Brunauer-Emmett-Teller (BET) specific surface area (SBET) and average pore size and pore volume of pure MCS, NiSe2 and MCNS-10 samples by N2 adsorption-desorption isotherms at 77 K as shownFig. 5 and Table 1 . As shown inFig. 5 , the all samples exhibited IV type isotherms with H3 hysteresis loops, indicating that they had mesoporous structure [42]. The SBETwas augmented from 12 to 15 m2 g-1after loading MCS onto surface of NiSe2, this was because the cubic NiSe2 provide enough space for anchoring of MCS nanoparticles, which effectively prevent the occurrence of agglomeration. In addition, the increased surface area of composite catalyst MCNS-10 exposing more activity sites, which enhancing photocatalytic hydrogen evolution performance [43]. In short, the change of SBET of MCNS-10 was consistent with the alter in morphology for MCNS-10 composite in TEM images.