Sites for High Efficient Photocatalytic Hydrogen Evolution on a Limited-Layered MoS2 Cocatalyst Confined on Graphene Sheets―The Role of Graphene

Abstract

The development of an advanced cocatalyst is critical for improving the efficiency of the photocatalytic hydrogen evolution reaction. Noble metals such as platinum (Pt) have been identified to be the most active cocatalyst for this reaction; however, due to their low-abundance, high cost, their usage in the scale-up setup is impeditive. Here, we report a high active cocatalyst, limited-layered MoS2 confined on RGO sheets as an alternative of Pt, for hydrogen evolution in dye-sensitized photocatalytic systems. Growing a MoS2 cocatalyst on RGO sheets provides more available catalytically edge sites and thus exhibits much higher activity than large aggregated pristine MoS2 particles under visible light irradiation (≥420 nm). The apparent quantum efficiency (AQE) of 24% at 460 nm over an Eosin Y-sensitized MoS2/RGO photocatalyst has been achieved. In addition, the electrical coupling and synergistic effect between MoS2 and RGO sheets greatly facilitate the efficient electron transfer from photoexcited dye to the active edge sites of MoS2; as a result, the prolonged lifetime of photogenerated electrons and the improved charge separation efficiency have been accomplished, and the photocatalytic hydrogen evolution activity has been enhanced significantly. This work demonstrates that the structural integration of MoS2 with RGO will be a new promising strategy to develop a high efficient and low-cost non-noble metal cocatalyst for solar hydrogen generation.