High-capacity hydrogen storage in Li-decorated newly synthesized 2D polyaramid: Insights from density functional theory

Abstract

Using Density Functional Theory, a newly synthesised 2-dimensional polyaramid (2dpa) system decorated with Li is explored for its hydrogen storage capability, and interesting results are obtained. Various sites on 2dpa are studied to ascertain the finest location for Li-decoration. The optimum configuration for hydrogen storage is then achieved by successively adding H₂ molecules, till it satisfies the adsorption energy window as prescribed by DoE (0.2–0.7 eV/H₂). Li has a good binding energy of −2.78 eV on 2dpa, higher than the cohesive energy for Li and thus prevents any possibilities of clustering. Yet the clustering has been checked by calculating the diffusion energy barrier for the Li atom which came to be around 1.92 eV. The average binding energy for H₂ on 2dpa + Li came to be −0.25 eV and the gravimetric weight percent with 3Li on 2dpa and 6H₂ molecules attached to each Li comes to be 10.62. Both values meet the conditions set by the US DoE for solid-state hydrogen storage systems. The thermal and dynamic stability of the system has been investigated using Ab initio Molecular Dynamics simulations and computing phonon spectra. Our theoretical results on newly synthesized 2D material may inspire the experimentalist to design a 2dpa-based high-capacity hydrogen storage device.