Effect of Graphene/MoS2 interface on Hydrogen Evolution Reaction

In a previous work, we demonstrated the performance of MoS2 synthesized on Reduced Graphene Oxide as a electrocatalyst to hydrogen evolution reaction (HER) and the role of graphene to avoid 3D growth of MoS₂.¹ The present work shows the improved performance as a electrocatalyst to HER of Molybdenum Disulfide (MoS₂) synthesized on Mechanical Exfoliated Graphene (MoS₂/GRA) instead of chemically Exfoliated Graphene. By X-ray Photoelectron Spectroscopy of the composites, we detected that the first layers of MoS₂ are bonded to oxygen of the RGO by chemically covalent bond (Mo-O-C) and absence of this bands to MoS₂ when synthesized on mechanical exfoliated graphene, as illustrated in figure 1a and 1b. The structure and morphology were characterized by Scanning Electron Microscopy and Transmission Electron Microscopy. The electrochemical characterizations shows that overpotential was significantly reduced when mechanically exfoliated graphene was used in the synthesis of composite (MoS₂/GRA), (see Figure 1c). A synergetic effect was observed, once pure materials were employed a poor performance was reported. Moreover, the interface structure is a key parameter on the acting of composite, taking account that the simple mix of both, chemically exfoliated graphene with MoS₂ and mechanically exfoliated Graphene with MoS₂, exhibited different on set values.