• Electric fields induce valence-dependent ion accumulation in graphene nanochannels • Double-peak interfacial layers emerge above moderate field strengths • Multivalent ions form stable near-wall confinement layers • Accumulation suppresses near-wall mobility and redistributes flow • Ion hydration and valence govern electro-driven confinement dynamics Graphene nanochannels subjected to external electric fields exhibit complex ion transport and accumulation behaviour that is strongly influenced by ionic charge, chemical identity, and hydration. While previous molecular dynamics studies have demonstrated electric-field-driven accumulation of selected ions near graphene interfaces, a systematic understanding of ion-specific dynamics, solvent coupling, and transport consequences remains incomplete. In this work, classical molecular dynamics simulations are employed to investigate the behaviour of mono-, di-, and trivalent metal ions (Na⁺, Mg²⁺, Ca²⁺, Cu²⁺, Zn²⁺, Ni²⁺, Fe²⁺, and Fe³⁺) confined within graphene nanochannels under externally applied electric fields. Time-resolved distance profiles reveal a two-stage response comprising an initial migration phase followed by field-dependent accumulation near the graphene walls, with pronounced ion-specific intermittency at intermediate field strengths. Spatial number density profiles demonstrate the emergence of symmetric double-peak structures at moderate to high fields, accompanied by solvent depletion in ion-rich interfacial regions. Direct comparisons across ionic species reveal a clear hierarchy of accumulation propensity governed by ionic valence and chemical identity. Analysis under varying applied driving forces at an intermediate electric field (0.50 V Å⁻¹) further shows that strong interfacial accumulation promotes increasingly localized ionic and solvent distributions within the graphene nanochannel, rather than uniformly enhancing transport. Together, these results establish a unified picture linking ion migration, accumulation, solvent restructuring, and transport under nanoconfinement. The findings provide new insight into ion-selective electro-nanofluidic behaviour in graphene nanochannels and offer guidance for the design of electrically tuneable filtration, sensing, and energy-related nanodevices.
R.A. Harris (Fri,) studied this question.