Understanding the Hydrogenation of Graphene

Since its discovery in 2004 [1], Graphene has attracted a great deal of attention due to its remarkable structural and electronic properties[2]. However, one of its main drawbacks is the lack of a gap in its electronic structure, which can limit its electronic applications. My advisor, Jorge Sofo theorized graphane in 2007[3], which is essentially a 2D hydrocarbon with one hydrogen atom attached to each carbon within the graphene lattice. This opens an insulating gap within the electronic structure, and graphane’s creation was shown to be energetically favorable. This new material remained in the realm of theory until 2009, when the group of A.K. Geim et al. in Manchester reported to have successfully hydrogenated graphene[4]. Their experimental results, however, brought up many interesting questions, such as the deviation of the lattice constant from theory, the large spread of lattice constants measured, and evidence suggesting less than full hydrogenation of graphene.

My research aims to understand the nature of hydrogen adsorption. To do this, I use a variety of tools, both computational and theoretical, to model the Graphene-H interaction and binding. Computationally, most of my work involves the use of VASP[5-8], a first-principles electronic simulation code which finds the electronic states of many body systems using Density Functional Theory (DFT). This code is run on and scales well with the CyberSTAR and Lion-X clusters here at Penn State. One calculation involved simulating the energetics of a single Hydrogen adsorbing onto graphene (See Figure 1), which showed a ~0.2 eV activation energy necessary for bonding. Once the Hydrogen has attached to the surface, there is also the matter of whether or not it can diffuse. Thi...

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