DFT Study on Molecular Hydrogen Physisorption on Graphene

초록

Over the past few decades, there has been extensive research to seek a solution for the issue of global warming caused from use of fossil fuels. One of the most challenging studies in this realm would be the development on exploitable hydrogen energy, since the hydrogen could be used as a clean and recyclable energy source in fuel cell. In this work, to investigate the physisorption properties, detailed DFT calculations on the interactions of molecular hydrogen, H2, on various poly-aromatic hydrocarbons (PAHs) as model systems for graphene sheets have been carried out. The results were compared to high-level ab initio calculation. The unit-cell approach implemented in the Dmol3 was examined using the n x n unit cell (n=1, 2, … , 8) approach. Physisorption orientations were also investigated to obtain favorable structures. It was predicted that ideal distance between two layers is about 5.5 ~ 6.0Å. The GGA (generalized gradient approximation) calculations were performed using the Perdew-Burke-Ernzerhof function, including the Grimme dispersion correction. Dispersion correction overestimates binding energy, but the optimized geometries were good agreement with experminetal finding. Additionally, to investigate the effect of defects or oxygen-containing functional groups, the system was modified by introducing some functional groups after removing some carbon atoms. The present work could expect to provide more useful and reliable information on the design of the graphene-based hydrogen storage.