Insight into the Effect of Highly Dispersed MoS2 versus Layer-Structured MoS2 on the Photocorrosion and Photoactivity of CdS in Graphene-CdS-MoS2 Composites

Designing a semiconductor CdS-based photo catalyst for H-2 evolution from water with high activity and stability is extremely desirable for practical application. We report the important morphological and structural influence of MoS2 cocatalyst on the photocorrosion and photoactivity of CdS that is carpeted on a graphene (GR) surface. Homogeneous dispersion of MoS2 nanopartides by a controlled photodeposition (PD) method produces the GR-CdS-MoS2 (PD) composite, which does not have the characteristic stacked layer structure of MoS2. However, this GR-CdS-MoS2 (PD) composite exhibits much higher activity and particularly antiphotocorrosion than the hydrothermal synthesized GR-CdS-MoS2 (HT) counterparts, which feature the characteristic MoS2 layer structure, toward photocatalytic water splitting under visible light irradiation. The characterization results indicate that homogeneous dispersion of tiny MoS2 for GR-CdS-MoS2 (PD) markedly improves the separation and transfer of charge carriers and provides the increased number of catalytic active sites afforded by the absence of the stacked layer structure of the MoS2 cocatalyst. This work provides direct evidence of the negative effect of the stacked layer structure of MoS2 on boosting the activity and photostability of CdS on the GR surface, which would guide the more rational use of MoS2 and GR as cocatalyst toward achieving a highly active and stable semiconductor-based composite photocatalyst for H-2 evolution.