Ab-initio study of hydrogen atom pairs adsorption on potassium doped graphene

The effects of the interactions of hydrogen (H) atoms on graphene (G) with potassium (K) pre-adsorbed, were predicted by means of first-principles calculations. The results were obtained with the pseudopotentials method and the generalized gradient approximation for the exchange-correlation potential. The structural parameters, bonding, electronic structure and magnetic properties of two H atoms on potassium doped graphene (2H-K/G) system are calculated by molecular dynamics. We found an important charge transfer from the K atom towards the G surface when an H atom was adsorbed, producing a chemical bonding transition from sp$^{2}$ to sp$^{3}$ in the bonded carbon atom. The binding energy per H atom was greater in the 2H-K/G system than both H-K/G and a H atom on the single G systems (H/G). The present results suggest that the hydrogen adsorption on graphene layer could be modulated by the pre-adsorption of potassium.