Theoretical design of a strain-controlled nanoporous CN membrane for helium separation

Abstract

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.

Pd/Pt embedded CN monolayers as efficient catalysts for CO oxidation

“…Results and discussion 3.1. Structure and Stability of Pd/Pt embedded CNThe optimized lattice parameter, corresponding C−N and C−C bond length of CN monolayer are 7.12, 1.34, and 1.51Å, respectively, coinciding with reported results [25,31,32]. We used 2 × 2 CN supercell containing 24 carbon and 24 nitrogen atoms, creating a hole surrounding by six sp 2 bonded nitrogen atoms, which are beneficial for Pd/Pt anchoring.…”

“…The optimized lattice parameter, corresponding C−N and C−C bond length of CN monolayer are 7.12, 1.34, and 1.51 Å, respectively, coinciding with reported results. [25,31,32] We used 2 × 2 CN supercell containing 24 carbon and 24 nitrogen atoms, creating a hole surrounding by six sp 2 bonded nitrogen atoms, which are beneficial for Pd/Pt anchoring. Taking Pd@CN as an example, it is indeed as expected that the Pd bonds to two N edge atoms with bond length of 2.20 Å and keeps its planar geometric structure undistorted after structural optimization [shown in Fig.…”

“…More importantly, the uniform nitrogen coordinators provides unique identification of active sites. Among these nitrogen−doped 2D carbon networks, CN has triggered intensive research in He separation, [31] H 2 storage [32] and O 2 evolution reaction. [29] Although intrinsic CN is inert in electrocatalytic processes, it is still attractive to study whether the transition metals−embedded CN system can exhibit promising catalytic performance with high stability and superior reactivity in the CO oxidation reaction.…”

Gas Separations using Nanoporous Atomically Thin Membranes: Recent Theoretical, Simulation, and Experimental Advances

“…In this regard, atomic-scale simulations have been carried out to estimate the gas permeances more precisely. Figure 4 summarizes the simulation results of gas permeation through NATM pores using molecular dynamics (MD) simulations, [59,61,63,64,66,67,[73][74][75] ab initio calculations, [29,70,83,[108][109][110][111][112][113][114][115][116][117][118][119][120][121] or a combination of both, [72,82,[122][123][124][125][126][127][128][129][130][131][132][133][134][135][136][137] as well as experimental results of gas permeation through individual graphene nanopores. [60,138] The gases considered in Figure…”

The electrical properties and modulation of g-C3N4/β-As and g-C3N4/β-Sb heterostructures: a first principles study

“…Researchers have been working on nding other 2D materials. Recently, hexagonal boron nitride (h-BN), 10,11 transition metal dichalcogenide (TMD), [12][13][14] graphitic carbon nitride, [15][16][17][18] and phosphorene [19][20][21] have been synthesized successfully. Thereaer, ultrathin 2D van der Waals heterojunctions and their devices have received extensive attention.…”