Unraveling the potential of graphene for hydrogen storage: insights from molecular dynamics simulations

Abstract

This thesis investigates the enhancement of hydrogen storage capabilities of graphene and its derivatives through various modifications, utilizing molecular dynamics simulations (MDS) to analyze the effects of temperature, pressure, strain, vacancy defects, and atomic-level modifications on hydrogen adsorption and desorption behaviors. The research introduces a novel method for potential energy distribution (PED) estimation to explore the gravimetric density of hydrogen adsorption, providing a comprehensive simulation framework for studying these phenomena under diverse conditions. The initial part of the study focuses on the hydrogen adsorption behavior on monolayer graphene, revealing that low temperatures and high pressures are optimal for achieving high gravimetric densities. The introduction of strain and vacancy defects in graphene nanosheets (GNS) shows significant increases in hydrogen storage capacity, with specific defects and strains identified as particularly effective for enhancing adsorption. Furthermore, the thesis delves into the potential of titanium-decorated polycrystalline graphene (Ti-PGs) and examines the influence of grain boundaries and Ti atom concentration, finding that these factors substantially augment hydrogen adsorption. Additionally, nitrogen doping and titanium adatom implantation on graphene sheets with vacancy defects (D-G) are explored as methods to further increase hydrogen storage efficiency. The study demonstrates that these atomic-level modifications can lead to notable improvements in hydrogen storage capacities, with certain configurations achieving significantly higher adsorption rates and capacities compared to pristine graphene sheets. Overall, this research provides valuable insights into the mechanisms of hydrogen adsorption by graphene and its derivatives, highlighting the potential of structural and compositional modifications for optimizing graphene-based materials for efficient and reversible hydrogen storage. The findings contribute to the development of novel materials and methodologies for hydrogen storage, addressing one of the critical challenges in the utilization of hydrogen as a sustainable and clean energy carrier. Keywords: Atomistic modeling; Graphene defects; Graphene doping; Hydrogen storage; Molecular dynamics simulation; Polycrystalline graphene.