Interfacial Properties of Two-dimensional CdS/Graphene Nanocomposites
Austin Atsango ’18, Reid Smith ’18, and Leah Isseroff Bendavid (Chemistry)
Cadmium sulfide (CdS) is an attractive photocatalytic material due to its cheap production cost and narrow bandgap, which allows for the absorption of most visible light. Unfortunately, CdS has a low photocatalytic efficiency due to multiple properties such as aggregation, photocorrosion, and electron-hole recombination. The photocatalytic performance of CdS can be improved by coupling it with graphene in a nanocomposite, in which interfacial contact is a key factor in its effectiveness. One promising way to achieve maximum interfacial contact is by combining CdS nanosheets with graphene sheets. This study explored the photocatalytic potential of two-dimensional graphene/CdS nanocomposites by using density functional theory (DFT) to analyze the atomic-level interactions and electronic properties of the interfaces. 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 two-dimensional graphene/CdS nanoarchitecture. The optimized structures exhibited high interplanar distances and low adhesion energies, which are indicative of weak interfacial coupling. Bader charge analysis showed no charge transfer between CdS and graphene, and the electronic structures of both CdS and graphene in the interface were nearly identical to those of the isolated layers, further demonstrating the weak chemical interaction between the layers. The weak coupling and minimal interfacial adhesion signify the low photocatalytic potential of the two-dimensional graphene/CdS nanocomposite. Future work will search for methods to improve interfacial coupling in these nanocomposites by exploring doping of CdS, graphene, or both layers.