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Title: Theoretical investigations of the effect of graphite interlayer spacing on hydrogen absorption

Abstract

This study investigates the absorption of hydrogen molecules between graphite layers using both first principles calculations and classical grand canonical Monte Carlo simulations. While a recent theoretical study showed that graphite layers have high storage capacity at room temperature, previous simulation results on hydrogen-graphite systems showed otherwise. Our first-principles calculations suggest that it is possible to store hydrogen molecules between the graphene layers if the energetically unfavorable initial absorption stage could be overcome. The barrier to the initial absorption originates from the large lattice strain required for H2 absorption: small amounts of initial absorption cause an interlayer expansion of more than 60%. To determine if significant storage is indeed possible at finite temperature (and pressure), we performed grand canonical Monte Carlo H2-absorption simulations with variable graphite interlayer spacing. Using two different potentials for the H2-C interaction, we found low H2 mass uptake at room temperature and moderate pressures (e.g., close to 2 wt-% at 298 K and 5 2 MPa.). Our results suggest that a graphite pore width or interlayer spacing around 6 has the optimum absorption capacity. PACS numbers: 68.43.-h, 81.05.Uw, 82.20.Wt, 83.10.-y

Authors:
 [1];  [1];  [1];  [1]
  1. ORNL
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
932014
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review B; Journal Volume: 76; Journal Issue: 16
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ABSORPTION; CAPACITY; GRAPHITE; HYDROGEN; STORAGE; STRAINS

Citation Formats

Aga, Rachel S, Fu, Chong Long, Krcmar, Maja, and Morris, James R. Theoretical investigations of the effect of graphite interlayer spacing on hydrogen absorption. United States: N. p., 2007. Web. doi:10.1103/PhysRevB.76.165404.
Aga, Rachel S, Fu, Chong Long, Krcmar, Maja, & Morris, James R. Theoretical investigations of the effect of graphite interlayer spacing on hydrogen absorption. United States. doi:10.1103/PhysRevB.76.165404.
Aga, Rachel S, Fu, Chong Long, Krcmar, Maja, and Morris, James R. Mon . "Theoretical investigations of the effect of graphite interlayer spacing on hydrogen absorption". United States. doi:10.1103/PhysRevB.76.165404.
@article{osti_932014,
title = {Theoretical investigations of the effect of graphite interlayer spacing on hydrogen absorption},
author = {Aga, Rachel S and Fu, Chong Long and Krcmar, Maja and Morris, James R},
abstractNote = {This study investigates the absorption of hydrogen molecules between graphite layers using both first principles calculations and classical grand canonical Monte Carlo simulations. While a recent theoretical study showed that graphite layers have high storage capacity at room temperature, previous simulation results on hydrogen-graphite systems showed otherwise. Our first-principles calculations suggest that it is possible to store hydrogen molecules between the graphene layers if the energetically unfavorable initial absorption stage could be overcome. The barrier to the initial absorption originates from the large lattice strain required for H2 absorption: small amounts of initial absorption cause an interlayer expansion of more than 60%. To determine if significant storage is indeed possible at finite temperature (and pressure), we performed grand canonical Monte Carlo H2-absorption simulations with variable graphite interlayer spacing. Using two different potentials for the H2-C interaction, we found low H2 mass uptake at room temperature and moderate pressures (e.g., close to 2 wt-% at 298 K and 5 2 MPa.). Our results suggest that a graphite pore width or interlayer spacing around 6 has the optimum absorption capacity. PACS numbers: 68.43.-h, 81.05.Uw, 82.20.Wt, 83.10.-y},
doi = {10.1103/PhysRevB.76.165404},
journal = {Physical Review B},
number = 16,
volume = 76,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • Layered molybdenum disulfide has demonstrated great promise as a low-cost alternative to platinum-based catalysts for electrochemical hydrogen production from water. Research effort on this material has focused mainly on synthesizing highly nanostructured molybdenum disulfide that allows the exposure of a large fraction of active edge sites. Here we report a promising microwave-assisted strategy for the synthesis of narrow molybdenum disulfide nanosheets with edge-terminated structure and a significantly expanded interlayer spacing, which exhibit striking kinetic metrics with onset potential of -103 mV, Tafel slope of 49 mV per decade and exchange current density of 9.62 × 10-3 mA cm-2, performing amongmore » the best of current molybdenum disulfide catalysts. Besides benefits from the edge-terminated structure, the expanded interlayer distance with modified electronic structure is also responsible for the observed catalytic improvement, which suggests a potential way to design newly advanced molybdenum disulfide catalysts through modulating the interlayer distance.« less
  • In this study, layered molybdenum disulfide has demonstrated great promise as a low-cost alternative to platinum-based catalysts for electrochemical hydrogen production from water. Research effort on this material has focused mainly on synthesizing highly nanostructured molybdenum disulfide that allows the exposure of a large fraction of active edge sites. Here we report a promising microwave-assisted strategy for the synthesis of narrow molybdenum disulfide nanosheets with edge-terminated structure and a significantly expanded interlayer spacing, which exhibit striking kinetic metrics with onset potential of -103 mV, Tafel slope of 49 mV per decade and exchange current density of 9.62 × 10 -3more » mA cm -2, performing among the best of current molybdenum disulfide catalysts. Besides benefits from the edge-terminated structure, the expanded interlayer distance with modified electronic structure is also responsible for the observed catalytic improvement, which suggests a potential way to design newly advanced molybdenum disulfide catalysts through modulating the interlayer distance.« less