Perpustakaan Digital ITB

Density functional theory (DFT) method was employed in simulation of molecular hydrogen adsorption and the influence of impurities on electronic band structure of graphene. The hydrogen adsorption simulation could give us a picture to see whether graphene is appropriate to be applied in hydrogen storage system or not, since today people are still investigating the best mechanism of hydrogen storage in mobile fuel cell application. The result shows that graphene has opportunity for this purpose, but unfortunately is still not applicable due to adsorption temperature issue. We find a weak interaction between graphene and molecular hydrogen H2 with binding energy of approximately 18 meV. The strongest binding energy is achieved when H2 is placed on the top of carbon atom of graphene with orientation perpendicular to the graphene plane. Due to this small binding energy, H2 desorption process is predicted to work at very low temperature which makes this system cannot be used in practical. Some modification of graphene structure may fix this problem, that will be our next study. In another case; that is about the influence of impurities on band structure of graphene, electronic structure of pure graphene shows no band gap. The similar result is also found after H2 adsorption, still, no band gap revealed. The gap starts to open when atomic N and H are attached on the graphene surface. Indirect band gaps of graphene-H and graphene-N systems revealed with 2.67 and 4.68 eV in width respectively. This leads us to make graphene as a strong candidate in electronic device application since the energy band gap can be controlled by selecting kinds of impurity.