Tuning Hydrogen Storage Properties of Li- and Na-Decorated 3D Carbon-Honeycomb through a Physisorption Process

Abstract

Understanding the adsorption, desorption, and diffusion of hydrogen within a three-dimensional carbon-honeycomb (C-h) is crucial in order to use it for efficient reversible H2 storage. By employing dispersion-corrected density functional theory (DFT-D2), this study investigates the suitability of lithium and sodium decorations on a C-h structure for H2 affinity by polarization mechanisms. We showed that Li- and Na-decorated C-h adsorbed the hydrogen molecule with adsorption energy at least 2 times stronger than that of the pure C-h (−0.135 eV per H2). At saturation, a total of 22 and 20 H2 molecules were adsorbed around 4Li@C-h and 4Na@C-h channels with theoretical gravimetric densities of 5.95 and 5.00 wt %, respectively. Besides, the van’t Hoff desorption temperature estimation shows the realization of hydrogen desorption in a range much higher than the critical point of hydrogen. Activation barriers indicate that the H2 molecule can migrate rapidly within the channels of C-h during the storage/release cycles. Our numerical results suggest that Li-decorated C-h can be an efficient solid-state material for the hydrogen storage medium.