1. Study and Modification of the Graphene-Hydrogen adsorption barrier
Bonding C
Far C
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We have studied in detail the interaction between Graphene and Hydrogen, seeing the bonding mechanism which takes place. As a Hydrogen atom nears the Graphene plane, the system energy rises as the Hydrogen is repulsed by Graphene’s π band. However, this barrier is soon overcome by the puckering of the bonding Carbon atom, causing an sp3 bond which breaks the delocalization of the pz orbital involved.
Fluorine behaves rather differently by having no barrier of adsorption, due to its ionicity allowing for charge to transfer from the Graphene plane and attract the adsorbate coulombically before bonding takes place. We have developed a tight binding 3 electron model which takes into account this ‘tug-of-war’ between the C-C and C-H hopping integrals to model the barrier empirically. Coloumb interactions are also taken into account to compare Hydrogen and Fluorine’s differences on the weakening of graphene’s π band. DFT calculations allow us to ‘remove’ electrons from graphene at the Fermi level to probe the effect of charge on hydrogen adsorption. In practice, a gate voltage or AFM tip could allow charging of the graphene plane to facilitate hydrogenation greatly.
Arb.
Units
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