Molecular Simulation of Interfacial Chemistry of Oxygen and Water Molecules Within Defective Graphene/MoS2 Heterojunctions

The graphene/MoS2 composite is a functional heterostructure with broad applications that leverage the synergistic properties of its constituents. Generally, small ambient molecules might penetrate and adsorb into the interlayer of graphene/MoS2 and interact with surface defects, leading to chemical reactions within the confined spaces. Currently, the interfacial interaction and reaction mechanisms remain largely unclear. Herein, we employed density functional theory and ab initio molecular dynamics simulations to investigate the interfacial adsorptions and reactions of O2 and H2O molecules at the Graphene/MoS2 interfaces with various vacancy types of MoS2 surfaces. Various mechanisms and pathways have been identified for the thermodynamic trends and kinetic barriers in interlayer reactions. It is demonstrated that the pristine Graphene/MoS2 is inert for molecular interlayer adsorption. However, there are obvious chemical reactions at the defect-involved G/MoS2 interfaces. Specifically, the dissociation of molecular oxygen can induce surface oxidation, accompanied by the restoration of the electronic properties of graphene/MoS2. The water molecule can undergo spontaneous dissociation at the defect sites, exhibiting enhanced activity for water splitting. As compared with bare MoS2, the hybrid interfaces of graphene/MoS2 can alter the chemical reactivities of adsorbed molecules. This work provides new insights into the interlayer chemistry for heterojunction interfaces.