Interfacial Properties of Two-dimensional CdS/Graphene Nanocomposites

Cadmium sulfide is an attractive photocatalytic material that is challenged by low photocatalytic efficiency. The photocatalytic performance of CdS can be improved by pairing it with graphene in a nanocomposite with strong interfacial coupling. Interfacial contact would be maximized in a two-dimensional nanosheet bilayer architecture. This study explored the photocatalytic potential of a graphene/CdS bilayer by using density functional theory (DFT) to analyze the atomic-level interactions and electronic properties of the interface. We first determined an appropriate DFT method for bulk CdS and graphene, validating the accuracy of the Perdew-Burke-Ernzerhof (PBE) and Heyd-Scuseria-Ernzerhof (HSE) functionals. PBE and HSE were then used to examine the interfacial interactions in various models of the graphene/CdS nanocomposite. The optimized structures exhibited high interplanar distances and low adhesion energies, which are indicative of weak interfacial coupling. Bader charge analysis and interfacial electronic structures also suggest a weak chemical interaction between the layers. The weak coupling and minimal interfacial adhesion signify the low photocatalytic potential of the pure graphene/CdS nanocomposite. We then examined the potential to improve interfacial coupling in these nanocomposites via boron and nitrogen doping and codoping of graphene. The dopants considered did not significantly modify the interfacial interactions. Currently, we are studying the adhesion of various models of graphene oxide to the CdS monolayer, and examining if the epoxy and hydroxyl functional groups result in stronger interfacial interactions. Additionally, we are comparing the two-dimensional bilayer structure to the adhesion of pure and doped graphene on the CdS(0001) and CdS(000-1) surface, which may exhibit differing trends due to the undercoordination of the surface atoms.