Electrostatic Modulation of Nanoporous Phosphorene for Water Desalination: Simulation Insights

Phosphorene, with its atomic-scale thickness, anti-fouling, stability, and self-passivation properties, is a potential candidate for large-scale desalination. Here, we investigate charged but overall neutral phosphorene nanopores of varying sizes namely, D16 (~28 Ų), D18 (~41 Ų), and D20 (~38 Ų) using molecular dynamics simulations to explore the effect of electrostatic edge modulation on water and ion transport. Five distinct spatial charge distributions (CD-1 to CD-5) were applied to the nanopore edges, introducing local asymmetries while preserving global charge neutrality. The D18 nanopore exhibited the highest water flux, for CD-4 and CD-5 distribution, which feature oppositely charged feed and permeate sides. These distributions generate strong axial electrostatic fields that align water molecules, reduce energy barriers, and significantly enhance transport efficiency compared to the more symmetric CD-1 to CD-3. Ion rejection rates for Na⁺ and Cl⁻ ranged from 95% to 100%, supported by steep Potential of Mean Force (PMF) profiles that indicate robust energy barriers to ion permeation. Molar concentration and water density profiles further reveal effective ion exclusion and enhanced structuring within the pore. These findings highlight the critical role of charge patterning and pore geometry in tuning membrane performance, establishing electrostatic modulation of charge-neutral phosphorene as a viable strategy for highefficiency water desalination.