MXene-based gas separation membranes with sorption type selectivity

We report on the specific properties of O- and OH-terminated Ti3C2Tx nanosheets contributing the permeance of MXene membranes with sorption type selectivity. Thin MXene selective layers on porous support demonstrated separation factor for NH3/H-2 pair over 50 with ammonia permeance up to 5.0 m(3)(STP).m(-2).bar(-1).h(-1) facilitated for humid medium and separation factor for H2O/N-2 over 1000 with water permeance over 30 m(3) (STP).m(-2).bar(-1).h(-1) close to P-0(H2O). According to QCM and GIWAXS studies, high permeance and selectivity of membranes towards ammonia and water vapors are attributed both to ultimate sorption capacity for basic vapors and condensation-induced expansion of the interlayer space. Sorption capacity of MXene over 0.045 g.g (MXene)(-1) at 0.3P 0 for both NH3 and H2O, significantly exceeds the sorption capacity for permanent gases. Calculations of the diffusion coefficient suggest labyrinthine transport of vapors. For permanent gases no variation of diffusion coefficients was observed with feed pressure, indicating Knudsen diffusion mechanism. Diffusion coefficient of strongly absorbed gases significantly increases with pressure. According to GIWAXS the effect was attributed to the increase of the interlayer distance with saturation of membrane with vapors and reduction of activation barriers for hopping diffusion. Demonstrated characteristics of Ti3C2Tx nanosheets makes it a promising candidate for developing of ammonia selective membranes for Haber-Bosch process membrane extractors.

Automated summary

The specific properties of O- and OH-terminated Ti3C2Tx nanosheets contribute to the permeance and sorption type selectivity of MXene membranes. These membranes demonstrate high separation factors and permeances for ammonia and water vapors, with strong sorption capacities and labyrinthine transport. The diffusion coefficient of strongly absorbed gases increases with pressure, and the interlayer distance expands, reducing activation barriers for hopping diffusion. Demonstrated characteristics make Ti3C2Tx nanosheets a promising candidate for developing ammonia selective membranes.