Thermal conductivity and structural behavior of confined H₂ from molecular dynamics simulation

Abstract In this work, we perform equilibrium molecular dynamics simulation to study the thermal conductivity of hydrogen molecules (H₂) under extreme confinement within graphene nanochannel. We analyze the structural behavior of H₂ molecules inside the nanochannel and also examine the effect of nanochannel height, the number of H₂ molecules, and temperature of the system on the thermal conductivity. Our results reveal that H₂ molecules exhibit a strong propensity for absorption onto the nanochannel wall, consequently forming a dense packed layer in close to the wall. This phenomenon significantly impacts the thermal conductivity of the confined system. We made a significant discovery, revealing a strong correlation between the mass density near the nanochannel wall and the thermal conductivity. This finding highlights the crucial role played by the density near the wall in determining the thermal conductivity behavior. Surprisingly, the average thermal conductivity for nanochannels with a height (h) less than 27 Å exhibited an astonishing increase of over 12 times when compared to the bulk. Moreover, we observe that increasing the nanochannel height, while the number of H₂ molecules fixed, leads to a notable decrease in thermal conductivity. Furthermore, we investigate the influence of temperature on thermal conductivity. Our simulations demonstrate that higher temperature enhance the thermal conductivity due to increased phonon activity and energy states, facilitating more efficient heat transfer and higher thermal conductivity. To gain deeper insights into the factors affecting thermal conductivity, we explored the phonon density of states. Studying the behavior of hydrogen in confined environments can offer valuable insights into its transport properties and its potential for industrial applications.