Strained graphitic carbon nitride for hydrogen purification

Hydrogen purification from a mixture of gas is a critical step in hydrogen production as an energy source and other clean energy applications. Recently gas purification using membranes with sub-nanometer pores, such as porous graphene has offered an attractive option which purifies the targeted gas from other impurity gases based on size exclusion exploiting the differences in the gases' molecular size. Using a combination of density functional theory (DFT) and molecular dynamic (MD) simulations, we demonstrate that graphitic carbon nitride (g-C3N4), a graphene like 2-dimensional nanomaterial can effectively purify H2 from CO2 and CH4. However, under neutral conditions the H2 flux across the membrane is comparatively weak, and our theoretical analysis shows that the flux can be significantly improved by widening the pore area via applying biaxial strains as low as 2.5% and 5% on the membrane. Interestingly, the strain tuning only improves the membranes H2 permeability, while its excellent H2/CO2 and H2/CH4 selectivity is not compromised.