A novel lithium-decorated GeC5 monolayer for promising hydrogen storage: A DFT study

Hydrogen is recognized as a clean and sustainable energy source, and the use of porous two-dimensional (2D) materials to advance the efficiency and viability of hydrogen storage systems in future energy applications is a key research focus. Herein, a comprehensive investigation has been conducted to assess the potential of the novel 2D germa-graphene GeC5 decorated with lithium (Li) atoms for hydrogen storage, employing the density functional theory (DFT) approach. Our analyses revealed that the calculated adsorption energy of the H2 molecule on the pristine GeC5 surface is outside the range required for practical hydrogen storage applications. However, the addition of Li atom significantly enhances the hydrogen adsorption energy. Our findings indicate that each Li atom can adsorb up to three H2 molecules, with a favorable adsorption energy of -0.25 eV. Considering that Li atoms do not show a cluster tendency, eight Li atoms were placed on either side of the twodimensional surface of GeC5 to maximize the H2 molecules storage. Our results demonstrate that the system can accommodate up to 24H2 molecules with an adsorption energy of -0.22 eV. This configuration offers an exceptional storage capacity, reaching 7.62 wt%, exceeding the goals of U.S. Department of Energy (DOE) target of 5.5 wt% and outperforming numerous other 2D materials. Moreover, the measured desorption temperature (TD) greatly exceeds the critical point of hydrogen, which validates the reversibility of the hydrogen adsorption process. Overall, the novel Li-decorated GeC5 monolayer offers remarkable potential as an efficient carrier for hydrogen adsorption and release, owing to its remarkable properties, paving the way for significant advances in sustainable energy technologies.