3.4 UV-vis DRS analysis
A comparison of the UV-vis diffuse reflection spectroscopy (DRS) of MCS, NiSe2, MCNS composite were displayed in Fig. 4a . Pure NiSe2 exhibited high adsorption coefficient throughout in the visible light and near infrared regions, which was related to the metallic character [33]. The absorption edge of pure MCS solid solution was approximately 560 nm. With the increasing of NiSe2 amount, the absorption intensity peak for composite catalyst was obviously increased at the 520-800 nm regions, which were ascribed to intrinsic absorption of NiSe2 and gradual deepening of the catalyst color. The light absorption efficiency and photocatalytic performance of composite catalyst were thus vastly improved [41], which was also one of the most important reasons for the improved hydrogen production performance of the catalyst. In addition, Fig. 4b present the corresponding energy band gaps (Eg) of MCS and MCNS-10 were estimated by drawing on the Tauc plots of (ahv)2 versus hv . The corresponding energy band gap values of MCS and MCNS-10 were estimated to be 2.26 and 2.2 eV, respectively. It could be seen that the improvement of the light absorption performance was related to the decrease of the band gap values.