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 photocatalyst for H₂ 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 nanoparticles 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 H₂ evolution