Investigação do armazenamento de hidrogênio em materiais bidimensionais via teoria do funcional da densidade

Abstract

With the increasing growth of energy demand and the pollution caused by fossil fuels, the need to search for efficient clean energy sources arises. Among the various possibilities, hydrogen emerges as a favorable candidate due to its high energy density and the fact that it does not generate pollutant emissions during its use. However, its storage remains a limiting factor due to the requirement of high pressures or extremely low temperatures. Among the alternatives, solid-state storage, especially through adsorption on two-dimensional materials, appears promising, eliminating the need for high pressures and extreme temperatures. Therefore, this work explores, through simulations employing density functional theory, the use of two two-dimensional materials for hydrogen storage: the NetY-B4N6, proposed and theoretically characterized in this work, and Dodecanophene, recently reported in the literature. Regarding NetY-B4N6, our results indicate its mechanical and dynamical stability, along with a metallic behavior. Concerning hydrogen storage, it is able to stably adsorb 32 H2 molecules with an average adsorption energy of −0.180 eV/H2, leading to a gravimetric storage capacity of 11.26 wt%. The interaction between the molecules and the monolayer occurs through van der Waals forces. The desorption temperature can reach values close to room temperature under low-pressure conditions. Dodecanophene was investigated in both its pristine form and in forms decorated with Na and K atoms. The results show that the decoration is mechanically and dynamically stable, with no tendency for clustering of the decorating atoms. In terms of storage, the pristine monolayer and the Na- and K-decorated structures were able to stably adsorb 28, 16, and 20 H2 molecules, with average adsorption energies of −0.200 eV/H2, −0.233 eV/H2, and −0.260 eV/H2, leading to gravimetric storage capacities of 10.59 wt%, 6.34 wt%, and 6.93 wt%, respectively. Thermodynamic analysis indicates that reversible storage is possible. The results for the four investigated structures are in agreement with the hydrogen storage criteria established by the U.S. Department of Energy (DOE). Therefore, the two-dimensional materials studied in this work are promising candidates for future hydrogen storage applications.