Microscopic Insight into Water Desalination through Nanoporous Graphene: The Influence of the Dipole Moment

Nanoporous graphene membranes with controllable pore size and chemical functionality may be one of the most desirable materials for water desalination. Herein, we investigate desalination performance of hydrogen-functionalized nanoporous graphene membranes. The charge values on hydrogen atoms (q_H) and carbon atoms at the pore rim are systematically adjusted. For q_H > 0, the flow rate decreases as q_H increases, whereas for q_H < 0, the flow rate tends to increase first and then decrease with increasing q_H, yielding a peak at ∼ -0.2 e. Moreover, nanopores with large dipole moments at the rim have little effect on the salt rejection. The calculated oxygen and hydrogen density maps, the potential of mean force for water molecule and salt ion passage through the nanopores, and the coordination number unveil the mechanisms underlying water desalination in nanoporous graphene. This work may inspire the design and improvement of two-dimensional membranes for water desalination.