On the Chemistry and Mobility of Hydrogen in the Interstitial Space of Layered Crystals H-BN, MoS2 and Graphite

10 December 2018, Version 1
This content is a preprint and has not undergone peer review at the time of posting.

Abstract

Recent experiments have demonstrated transport and separation of hydrogen isotopes in layered materials, such as hexagonal boron nitride and molybdenum disulphide. Here, based on first-principles calculations combined with well-tempered metadynamics simulations, we report the chemical interactions and mobility of protons (H+) and protium (H atoms) in the interstitial space of these layered materials. We show that both H+ and H can be transported between the layers of h-BN and MoS2 with low free energy barriers, while they are immobilized in graphite, in accordance with the experimental observations. In h-BN and MoS2, the transport mechanism involves a hopping process between the adjacent layers, which is assisted by the low- energy phonon shear modes. Defects present in MoS2 suppress the transport and act as traps for H species.

Keywords

proton and atomic hydrogen transport
2D membranes, quantum confinement
density functional theory
well-tempered metadynamics simulations
free energy landscape

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