Highly-efficient hydrogen purification with the T-C3N2 membrane via strain and charge engineering as well as their synergistic effect

Abstract

The efficient separation and purification of high-purity hydrogen is imperative and desirable. We systematically explored the H2 purification performance of the T-C3N2 membrane with and without biaxial compressive (BC) strain and charge engineering by using MD simulations and DFT calculations. We found that the pure T-C3N2 membrane has relatively poor H2 selectivity as CO2 can also permeate through the membrane, and two modulation methods of BC-strain and charge were thus introduced separately to enhance the H2 separation performance for the first time. The T-C3N2 membrane with BC-strains modulation (1 %–3%) has excellent H2 permeance of 1.60 × 107–1.85 × 107 GPU at 300 K with 15.6 % enhancement with respect to the pure T-C3N2 membrane. The selectivity of H2 over gases (CO, N2, CO2, H2O, CH4) was drastically improved, for example, H2/CH4 is enhanced from 5.8 × 1020 to 2.1 × 1036 under 3 % strain engineering. The introduction of charge (1e ∼ 3e, 1e−–2e−) also enhances the H2 permeance of 1.47 × 107 ∼ 1.68 × 107 GPU and the selectivity at 300 K. In particular, the charge (1e) and (1e−) modulations exhibit a desired permeance-selectivity trade-off for H2 purification with the enhancement of 5 % permeability and at least 1.3 times selectivity of H2 to other gases, respectively. Finally, the synergistic effect of BC-strain and charge on the H2 separation was studied, and it is much superior to separated BC-strain and charge engineering for H2 purification, where the H2 permeance enhances up to 1.86 × 107 ∼ 1.89 × 107 GPU, and the H2 selectivity at 300 K is also enlarged at least ten times compared with that of the most effective modification of the isolated 2 % BC-strain and 1e charge, indicating synergistic effect further enhances the H2 separation performance. Therefore, the excellent modulations of appropriate BC-strain and charge engineering, particularly for their synergistic effect make the T-C3N2 membrane a promising candidate for highly permeant and selective H2 separation and purification that would be easily realized experimentally.