Figure 7. Ti4C3 nanopores with pore density of (a) 10×1012 cm-2, (b) 3.54×1012 cm-2. (c) He/CH4 separation performance of 2.92 Å Ti4C3 nanopores with different pore density. The dashed lines represent the linear fitting lines.
To investigate the influence of pore density, we performed simulations of gas permeance at various pore densities and calculated their separation performance. Higher pore density implies a greater number of pores within the same area, as depicted in Figure 7a and7b . It has been observed that both He and CH4permeance gradually decrease as the pore density decreases. Moreover, our findings reveal a direct proportionality between gas permeance and pore density, as illustrated in Figure 7c . Interestingly, we observed that the pore density hardly affect the selectivity. This implies that by elevating the pore density, the gas permeance can be enhanced without deteriorating the selectivity.
In addition, the permeance of mixed gas through four kinds of MXene nanopores with various d were simulated (Figure 8 ), and the results indicate that the permeance of the mixed gas also rises withd increasing, and displays a cut-off effect around the gas molecule’s kinetic diameter (Figure 8a ), which aligns with the trend observed for single gases (Figure 8b ). Furthermore,P CH4 and P He of mixed gas simulation is quite close to corresponding permeance of single gas simulation, which could be attributed to that, each gas molecule passes through the nanopore quickly so that it does not affect other molecule passing through. Consequently, the selectivity of the mixed gas is quite close to corresponding ideal selectivity.