Study on hydrogen storage properties of Ca atom modified γ-graphyne

Hydrogen has emerged as an ideal energy source for addressing energy shortages and environmental pollution, owing to its abundant reserves, non - toxicity, and pollution - free nature. While hydrogen production is relatively straightforward, its storage remains a significant challenge. Thus, safe and efficient hydrogen storage is of utmost importance. Compared with other hydrogen storage methods, graphyne is a highly promising and safe hydrogen storage material. In this study, first - principles calculations based on density functional theory were employed to investigate the hydrogen storage performance of Ca - atom - modified graphyne and determine the optimal adsorption site of Ca atoms on graphyne through metal modification. The objective was to maximize the hydrogen storage capacity of Ca - modified graphyne. The key findings are as follows: The optimal adsorption site for a single Ca atom on graphyne is the T₁ site. For two Ca atoms, the most favorable adsorption mode is at two T₁ sites on the same side of graphyne. The 4Ca - GY system can stably adsorb up to 20 hydrogen molecules. The average adsorption energy of each hydrogen molecule is −0.133 eV, and the hydrogen storage mass ratio reaches 8.20 wt%, which far exceeds the 6.5 wt% specified by the DOE. Therefore, it can be regarded as an ideal hydrogen storage material.