Mechanical Force-Driven Charge Redistribution for Hydrogen Release at Ambient Conditions in Transition Metal-Intercalated Bilayer Graphene

TL;DR

This study introduces a mechanical force method to control hydrogen release from transition-metal-intercalated bilayer graphene at ambient conditions, using DFT calculations to optimize interlayer distances for efficient desorption.

Contribution

The paper demonstrates that external mechanical forces can precisely modulate hydrogen desorption temperatures in TM-intercalated bilayer graphene by adjusting interlayer spacing, a novel control strategy.

Findings

Hydrogen desorption occurs below specific interlayer distances for Sc, Ti, and V intercalation.

Charge transfer from TM d-orbitals to H2 antibonding orbitals remains constant, but redistribution affects interaction strength.

Mechanical force can effectively bring hydrogen occupancy to zero, enabling ambient-condition release.

Abstract

Transition-metal (TM) atom-functionalized nanomaterials are promising candidates for hydrogen storage due to their ability to adsorb multiple hydrogen molecules through Kubas interactions. However, achieving efficient hydrogen desorption at ambient conditions remains a critical challenge for practical use. Here, we present a novel approach to modulate the desorption temperature of hydrogen in TM-intercalated bilayer graphene (BLG) using external mechanical forces. By employing first-principles density functional theory (DFT) and thermodynamic occupancy probability calculations, we demonstrate that adjusting the interlayer distance allows for precise control over the interaction energy of H2, thereby facilitating its desorption at ambient conditions. Complete hydrogen desorption occurs when the interlayer distance is reduced below 4.7 {\AA}, 5.3 {\AA}, and 5.1 {\AA} for Sc-, Ti-, and V-intercalated BLG, respectively. Our findings suggest that external mechanical forces can effectively bring hydrogen occupancy to zero by minimizing charge transfer from the TM d-orbitals to H2 antibonding orbitals. Notably, while the total charge transferred from the TM atoms remains nearly constant at varying interlayer distances, its redistribution between the graphene layers and H2 fine-tunes the interaction strength. This approach can be extended to large interlayer distances, as supported by recent experiments on graphene oxide membranes [ACS Nano 12, 9309 (2018)]. Furthermore, recent experimental advances in noble gas and alkali metal intercalation in BLG highlight the potential of this approach to overcome the long-standing challenge of high desorption temperatures in TM-functionalized layered nanomaterials.