Strain-tunable self-passivated porous phosphorene for high-efficiency helium separation

Abstract

The skyrocketing demand for helium (He) has stressed the limitation of the global He storge. The helium-rich natural gas represents the most accessible resource of He, thus the development of effective ways to extract He from natural gas is of high priority on the research agenda. The membrane-based separation technique is regarded as a promising method for efficient He purification that might possibly mitigate the current He shortage. In this work, by employing first-principles calculations together with molecular dynamics simulations, we predicted that both the strained and unstrained self-passivated porous phosphorene membrane can be used for efficient He harvest from natural gas. The results demonstrate that the porous phosphorene exhibits high He selectivities (104 ~ 1018) over impure molecules (CO, N2, CO2, CH4) and high He permeance of 10-3 mol m−2 s−1 Pa−1 at 300 K, both far exceeding the industry standard. More importantly, the He permeance of the porous phosphorene can be effectively regulated under moderate strain along with high selectivity. Therefore, the porous phosphorene presented in this study is a robust and mechanically-controlled semipermeable membrane for efficient He purification that holds a great prospect in industrial application.

Simulation Studies on Improved Separation of Helium and Helium Isotopes by Strain Modulated r-N-GY Monolayer Nanostructure

“…As demonstrated in previous studies, 20,21,28,29,74 the tradeoff between permeance and selectivity is the limiting factor that restricts the efficiency of separation membranes. Therefore, we inspected the selectivity of the strained r-N-GY membrane (along the AC direction) through MD simulations, as shown in Scheme 1c.…”

“…Calculation of the Selectivity and Permeance Based on DFT Energy Barriers. The He-selectivity with respect to other gases (S He/gas ) can be evaluated by the Arrhenius equation 21,29,52…”

“…The He-selectivity with respect to other gases ( S He/gas ) can be evaluated by the Arrhenius equation ,, S H e / g a s = r normalH normale r normalg normala normals = A normalH normale e − E H e / R T A normalg normala normals e − E g a s / R T where r is the diffusion rate, A is the diffusion prefactor of gas molecules, and E is the diffusion energy barrier. Consistent with former researches, we assign that the diffusion prefactor A = 10 11 s –1 of all gases is identical …”

“…Benefitted from the rapid development of nanotechnology, two-dimensional (2D) materials have emerged as superior candidates that are used as semipermeable membranes for membrane-based separation technique. , Especially that, a wealth of theoretical studies have focused on the use of 2D materials, either drilled or intrinsically porous, for He separation. − For instance, graphene, the most extensively studied 2D material, has been utilized for He separation and achieved great success if proper-sized defects and doping are introduced (PG, PG-ES1, 24 2DPPH, P-10, 26 BG). However, the fabrication of controllable defects in 2D materials requires precise nano-structure engineering that is costly and limited by large-scale production.…”