Hydrogen storage in carbon nanotubes: A Monte-Carlo simulation of adsorption at high pressure

The complementarily between Monte-Carlo predictive numerical simulations of adsorption and physical adsorption experiments enables to understand elementary mechanisms of gas adsorption on solid adsorbents. In the aim of hydrogen storage improvement, we have computed Monte Carlo simulations of hydrogen adsorption at room temperature and high pressure on carbonaceous solids to optimize micro-slit width and single-walled nanotube diameter that enable the highest hydrogen adsorption. The micro-slits are made by an array of parallel graphite basal planes (carbon atoms are located on the sites of an hexagonal compact structure). The single-walled carbon nanotubes are obtained by rolling up graphite basal planes. fn the Monte Carlo Grand Canonical simulations, we kept constant the volume of the cell, the temperature and the chemical potential. Pie took into account the description of the intermolecular interactions between hydrogen molecules, and, between hydrogen molecules and adsorbent carbon atoms. We described the potential energy between the gas molecules and the adsorbents by a Van der Waals interaction and between the gas molecules by a Van der Waals interaction. We optimized dimensions of the theoretical adsorbent models to obtain the highest excess surface adsorption of hydrogen. We obtained a value of 1 nm for the nanotube diameter. Furthermore, in order to enable hydrogen adsorption on the external surface of the nanotube walls, we optimized the distance between the walls to a value of 0.7 nm of the order of distance, we have obtained in the ideal slit width.