Three-dimensional diffusion of molecular hydrogen in graphdiyne: a first-principles study

Abstract

First-principles calculations with van der Waals correction included are carried out to investigate the intercalation and diffusion of molecular hydrogen in single-layer and bulk graphdiyne, which is crucial for understanding and improving the hydrogen storage capacity of graphdiyne. Different intercalation sites and hydrogen molecular orientations have been considered and compared. It is found that configurations with the axis of the hydrogen molecule parallel to graphdiyne layers are favoured. In contrast to graphite where hydrogen diffusion is restricted within the interlayer space, the unique porous structure of graphdiyne enables three-dimensional diffusion of hydrogen (in-plane diffusion and out-plane diffusion) with moderate energy barriers, thus ensuring easy hydrogen loading and unloading. The in-plane diffusion barriers largely depend on the interlayer distance, whereas the interlayer spacing has little effect on the out-plane diffusion barriers. This experimentally available novel carbon allotrope is expected to find applications in hydrogen storage.