Paper SS+AS-WeM6
Theoretical Investigation of the Structure and Properties of Titania/Graphene Hybrid Materials

Wednesday, November 12, 2014, 9:40 am, Room 312

We are using modeling to understand the properties of complex materials that show promise for catalysis, filtration and decontamination. These materials are of interests both for chemical defense, as well as in many industrial applications. The main focus of our modeling so far has been determining the structure and properties of mixtures of TiO2 nanoparticles(NPs) and small sheets of graphene. The synthesis technique for these materials was pioneered at ECBC. It involves synthesizing graphene from alizarin molecules in close contact with TiO2 NPs. This was expected to create a close connection between the graphene and TiO2 NPs, and improve their catalytic properties. However, the exact structure of the small graphene patches and how and where they bind to TiO2 is difficult to characterize experimentally. Our models have shown that the binding between graphene TiO2 is quite weak (on the order of 0.01eV/Carbon atom), and that it is not strongly dependant on the addition of O and OH to the surface of the graphene, or to the size of the graphene patches. This appears to confirm the experimental finding that the surface graphene can be removed from the TiO2 particles simply by rubbing. We also modeled the case where graphene is surrounded by TiO2 on both sides, and the binding in this case increases by nearly 2x, suggesting that graphene would prefer to bind between TIO2 NPs. This may be the explanation for the disappearance of the smallest (~5nm) sized pores from the TiO2 NP agglomerates upon addition of graphene. We also find that there is a non-trivial degree of charge transfer between graphene and TiO2, which can be expected to improve TiO2’s photo catalytic properties.