Molecular Design of H2 Storage/Release Devices: A Direct Ab Initio MD Study

TL;DR

This study uses computational methods to design a hydrogen storage and release system based on graphene, showing it can efficiently store and release hydrogen with low energy barriers.

Contribution

The paper introduces a novel theoretical design for hydrogen storage/release devices using graphene and ab initio molecular dynamics.

Findings

Hydrogen abstraction from hydrogenated graphene occurs without an activation barrier.

Hydrogen storage and release processes have low and negative activation energies, respectively.

Graphene-based devices are proposed as efficient for hydrogen storage and release.

Abstract

To advance a hydrogen-based energy society, the development of efficient hydrogen storage materials is essential. In particular, such materials are expected to be lightweight and chemically stable. Moreover, they must allow for easy storage and release of hydrogen. In this study, we theoretically designed hydrogen storage and release devices based on graphene (GR)—a lightweight and chemically stable material—using a direct ab initio molecular dynamics (AIMD) approach. The target reaction in this study is the hydrogen abstraction from hydrogenated graphene, H-(GR)-H, by hydrogen atom, resulting in molecular hydrogen formation: H-(GR)-H + H → GR-H + H2. Hydrogen atom (H) can be readily generated through the discharge of H2 gas. The calculated activation energy was −0.3 kcal/mol. The direct AIMD calculations showed that the hydrogen abstraction reaction proceeds without the activation barrier, and H2 is easily formed by the collision of H atom with the H-(GR)-H surface. For comparison, the addition reaction of hydrogen atom to the graphene surface was investigated: GR + H → GR–H. The activation energies were calculated to be 5–7 kcal/mol. These energetic profiles indicate that both hydrogen storage and release proceed with low and negative activation energies, respectively. On the basis of these calculations, H2-storage/release device was theoretically designed.

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