“…at room temperature, the selectivity for He/Ne and He/Ar are about 5.17×10 6 and 1.89×10 39 by subjecting to a −6% strain, respectively. The values are much superior than that of other theoretical results and surely acceptable for the industrial application [8,30,33]. …”
Designing an efficient membrane for He purification is quite crucial in scientific and industrial applications. Ultrathin membranes with intrinsic pores are highly desirable for gas purification because of their controllable aperture and homogeneous hole distribution. Based on the first−principles density function theory and molecular dynamics simulations, we demonstrate that the compressively strained graphitic carbon nitride (CN) can effectively purify He from Ne and Ar. Under a −6% strain, the CN monolayer with a suitable pore size presents an easily surmountable barrier for He (0.11 eV) but formidable for Ne (0.51 eV) and Ar (2.45 eV) passing through the membrane, and it exhibits exceptionally high selectivity of 5.17 × 10 6 for He/Ne and 1.89 × 10 39 for He/Ar, as well as excellent He permeance of 1.94 × 10 7 GPU at room temperature, superior to those of porous graphene and C 2 N membrane. Our results confirm that strain−tuned CN membrane could be potentially utilized for He separating from other noble gases.
“…at room temperature, the selectivity for He/Ne and He/Ar are about 5.17×10 6 and 1.89×10 39 by subjecting to a −6% strain, respectively. The values are much superior than that of other theoretical results and surely acceptable for the industrial application [8,30,33]. …”
Designing an efficient membrane for He purification is quite crucial in scientific and industrial applications. Ultrathin membranes with intrinsic pores are highly desirable for gas purification because of their controllable aperture and homogeneous hole distribution. Based on the first−principles density function theory and molecular dynamics simulations, we demonstrate that the compressively strained graphitic carbon nitride (CN) can effectively purify He from Ne and Ar. Under a −6% strain, the CN monolayer with a suitable pore size presents an easily surmountable barrier for He (0.11 eV) but formidable for Ne (0.51 eV) and Ar (2.45 eV) passing through the membrane, and it exhibits exceptionally high selectivity of 5.17 × 10 6 for He/Ne and 1.89 × 10 39 for He/Ar, as well as excellent He permeance of 1.94 × 10 7 GPU at room temperature, superior to those of porous graphene and C 2 N membrane. Our results confirm that strain−tuned CN membrane could be potentially utilized for He separating from other noble gases.
“…2), the D 2 permeance Q ( D
2 ) and the kinetic selectivity S ( D
2 / H
2 ) 19, 21, 33, 34 . Unlike the case of helium isotopes 21, 33 , the ZPE correction leads to a lower barrier for D 2 than that for H 2 , and thus the larger quantum tunneling probability of D 2 .Figure 2Quantum tunneling probability t ( E ) of hydrogen passing through the pore of C 2 N- h 2D membrane as a function of kinetic energy under different strains.…”
Isotopes separation through quantum sieving effect of membranes is quite promising for industrial applications. For the light hydrogen isotopologues (eg. H2, D2), the confinement of potential wells in porous membranes to isotopologues was commonly regarded to be crucial for highly efficient separation ability. Here, we demonstrate from first-principles that a potential barrier is also favorable for efficient hydrogen isotopologues separation. Taking an already-synthesized two-dimensional carbon nitride (C2N-h2D) as an example, we predict that the competition between quantum tunneling and zero-point-energy (ZPE) effects regulated by the tensile strain leads to high selectivity and permeance. Both kinetic quantum sieving and equilibrium quantum sieving effects are considered. The quantum effects revealed in this work offer a prospective strategy for highly efficient hydrogen isotopologues separation.
“…45 It should be noticed that the predicted selectivities could be actually reduced if the lowering of the penetration barrier due to deformation of the pores is taken into account: for the heavier species the larger lowering is expected (see Fig. S1) even if we do not consider that this effect can alter significantly the very favourable He/CH 4 and Ne/CH 4 probability ratios we have found.…”
Section: Force Fields and Quantum Dynamical Simulationsmentioning
Two-dimensional (2D) materials deriving from graphene, such as graphdiyne and 2D polyphenylene honeycomb (2DPPH), have been recently synthesized and exhibit uniformly distributed sub-nanometer pores, a feature that can be exploited for gas filtration applications. Accurate first principles electronic structure calculations are reported showing that graphdiyne pores permit an almost unimpeded helium transport while it is much more difficult through the 2DPPH openings. Quantum dynamical simulations on reliable new force fields are performed in order to assess the graphdiyne capability for helium chemical and isotopic separation. Exceptionally high He/CH 4 selectivities are found in a wide range of temperatures which largely exceed the performance of the best membranes used to date for helium extraction from natural gas.Moreover, due to slight differences in the tunneling probabilities of 3 He and 4 He, we also find promising results for the separation of the fermionic isotope at low temperature.
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