Efficient hydrogen storage in defective graphene and its mechanical stability: A combined density functional theory and molecular dynamics simulation study

Abdelrahman Hussein,Gagus Ketut Sunnardianto,Othonas A. Moultos,Carey Walters,George Bokas,Poulumi Dey

doi:10.1016/j.ijhydene.2020.11.068

Abstract

A combined density functional theory and molecular dynamics approach is employed to study modifications of graphene at atomistic level for better H2 storage. The study reveals H2 desorption from hydrogenated defective graphene structure, V222, to be exothermic. H2 adsorption and desorption processes are found to be more reversible for V222 as compared to pristine graphene. Our study shows that V222 undergoes brittle fracture under tensile loading similar to the case of pristine graphene. The tensile strength of V222 shows slight reduction with respect to their pristine counterpart, which is attributed to the transition of sp2 to sp3-like hybridization. The study also shows that the V222 structure is mechanically more stable than the defective graphene structure without chemically adsorbed hydrogen atoms. The current fundamental study, thus, reveals the efficient recovery mechanism of adsorbed hydrogen from V222 and paves the way for the engineering of structural defects in graphene for H2 storage.

Highlights

The demand for energy globally has significantly escalated in the past years
The surrounding environment is not considered within our study since H2 molecules in the surrounding environment have no effect on the desorption process of V222 / V211þH2
A comprehensive study of the H2 adsorption-desorption on a hydrogenated defective graphene structure and its mechanical stability were performed based on a combined Density Functional Theory (DFT)-molecular dynamics (MD) approach

Summary

Introduction

Energy consumption has increased in all major sectors including industry [1], transportation [2] and household [3] Most of this energy demand is met by burning fossil fuels, and only a small fraction from renewable energy sources [4]. Attempts to limit the fossil fuel consumption [5] to prevent the climate change caused by the emissions of green-house gases have stimulated the research for alternative, cleaner, sources of energy. In this context, several sources of clean energy e.g., biofuels [6], solar [7], hydrogen gas [8,9], have been proposed. H2 is an ideal green fuel because it is renewable, lightweight, nontoxic in nature, and available in enormous amount

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Conclusion