Fig. 3: H2/CO2 separation performance comparison of a series of porous-MXene nanosheet membranes and mechanism analysis.
a Mixed H2/CO2 separation performance of the 500-nm-thick nonporous-MXene nanosheet membranes and the porous-MXene nanosheet membranes after O3 treatment for different time. AFM images of the b nonporous- and (c) porous-MXene-O3-60s nanosheet membranes/VOx heterostructure (left). Raman peak area mapping at 197 cm−1 is shown before (0 h, top right) and after H2 passing through (3 h, bottom right). d Raman peak area ratio of 197 cm-1 before (A0) and after (A) H2 passing through the nonporous- and porous-MXene nanosheet membranes under the same roughness (19≤Ra≤20). The error bars in Fig. 3a, d denote the standard deviation obtained from measurements of three identically prepared membranes. e Four models of possible mass transport pathways through porous nanosheets assembled membrane. d1, d2, d1’, and dgas represent in-plane pore size, free interlayer spacing, overlapping pore size between adjacent porous nanosheets, and kinetic diameters of gas molecules, respectively. f Overlapping probability of the in-plane pores in the porous MXene nanosheets with the number of stacked layers by Monte Carlo simulations. Insets are the schematic diagrams of non-overlapping pores and overlapping pores. g Probability of pore overlapping of adjacent two-layer porous MXene nanosheets with different pore sizes and pore densities.
