Optimization of CdS@MoS2 core–shell nanorod arrays for an enhanced photo-response for photo-assisted electrochemical water splitting under solar light illumination
We prepared CdS@MoS2 core–shell nanorod arrays using a hydrothermal method and a subsequent electrodeposition. The well-defined physical features of the nanorod array of CdS@MoS2 provide both possibilities of a reverse biased P region and a forward biased N region. The preparation conditions (such as the hydrothermal reaction time, deposition time and precursor concentrations) were investigated to optimize the structures of the CdS@MoS2 core–shells, and thereafter to explore their effects on the photoelectrocatalytic activity. Specifically, the thickness of the MoS2 shell and the length of the CdS nanorods can be controlled through the deposition time, hydrothermal reaction time and precursor concentrations. The characterization results indicated that the structure of the CdS@MoS2 core–shell (length of the rods or layers of the shell) markedly influences the adsorption of light, and the separation and transfer of photogenerated charge carriers. Different proportions of MoS2 will result in different biased regions, in which a reverse bias will be beneficial for the photocatalytic activity, and a forward bias will have the opposite effect. The results indicated that a large portion of MoS2 will provide the great possibility of having a reverse biased P region under cathodic polarization, whereas, a large portion of CdS favors the reverse biased N region under anodic polarization. Herein, both of the reverse biased regions, either P or N, improve the photocatalytic activity. This investigation offers direct evidence of the effect of a CdS@MoS2 core–shell structure, when used as a photocathode, on improving the photo- and electrocatalytic activity, highlighting the importance of a more rational use of CdS/MoS2 cathodes toward achieving enhanced electrocatalytic activity through photo-assistance.