Roles of MoS2 and Graphene as Cocatalysts in the Enhanced Visible-Light Photocatalytic H2 Production Activity of Multiarmed CdS Nanorods

The incorporation of cocatalysts into semiconductors is proved to be an effective approach to improving the efficiency of the photocatalytic H-2 production. Noble metals such as Pt have been widely used as cocatalysts and can significantly improve the performance of photocatalytic H-2 production. However, owing to the high cost and low abundance, the use of Pt in practical applications is restricted. Herein, we report two well-known 2D layered materials, MoS2 and graphene, as highly active cocatalysts for H-2 production in CdS-based photocatalytic systems. The CdS-MoS2 and CdS-MoS2-graphene nanocomposites were prepared by using a facile two-step solvothermal method, and the morphologies of CdS and MoS2 can be well controlled. The as-prepared binary CdS-MoS2 nanocomposite exhibits the enhanced visible-light photocatalytic activity for H-2 production in lactic acid aqueous solution compared with a CdS-graphene nanocomposite and a conventional platinized CdS photocatalyst. Moreover, the ternary CdS-MoS2-graphene nanocomposite achieves the highest visible-light photocatalytic H-2 production activity of 621.3molh(-1) and the apparent quantum efficiency of 54.4% at =420nm. The enhanced photocatalytic activity of the CdS-MoS2-graphene nanocomposite can be primarily attributed to the positive synergistic effect between graphene sheets and thin MoS2 nanoplates. The graphene sheets can accelerate the efficient electron transfer from CdS nanorods to the active edge sites of MoS2 nanoplates, and the nanosized MoS2 can facilitate the photogenerated electrons participating in the photocatalytic H-2 production. The mechanisms for improving the photocatalytic performance of the MoS2- and/or graphene-modified CdS nanocomposites were proposed by using the electrochemical analysis and photoluminescence measurement.