Density functional calculations of efficient H₂ separation from impurity gases (H₂, N₂, H₂O, CO, Cl₂, and CH₄) via bilayer g-C₃N₄ membrane

Membrane technology has been used for H₂ purification. In this paper, the systematic density functional simulations are conducted to study the separation of H₂ from the impurity gases (H₂, N₂, H₂O, CO, Cl₂, and CH₄) by the bilayer porous graphitic carbon nitride(g-C₃N₄) membrane. Theoretically, the bilayer g-C₃N₄ membrane with a diameter of about 3.25 Å should be a perfect candidate for H₂ purification from these mixed gases, which is verified by the high selectivity (S) for H₂ over other kinds of gases (3.43×10²⁸ for H₂/N₂; 1.40×10²⁸ for H₂/H₂O; 1.60×10²⁶ for H₂/CO; 4.30×10¹⁴ for H₂/Cl₂; 2.50×10⁵⁵ for H₂/CH₄), and the permeance (P) of H₂ ($13mol/m^2\cdot s\cdot Pa$) across the bilayer g-C₃N₄ membrane at 300 K, which should be of great potential in energy and environmental research. Our studies highlight a new approach towards the final goal of high P and high S molecular-sieving membranes used in simple structural engineering. (paper)