Interfacially Regulated MXene‐Based Nanocomposite Membranes for Highly Selective Ion Transport and Salinity Gradient Energy Harvesting

ABSTRACT Achieving high ion selectivity, low membrane resistance, and long‐term stability remains a key challenge in developing two‐dimensional nanomaterial polymer composite membranes, where interfacial interactions critically influence membrane structure and ion transport. Here, we report interfacially regulated MXene‐based nanocomposite membranes in which humic acid (HA) mediates interactions between Ti 3 C 2 T x MXene nanosheets and a sulfonated polyethersulfone matrix. Structural characterization together with molecular dynamics simulations indicates that HA incorporation modifies MXene organization and interfacial interactions within the membrane, which are associated with enhanced ion‐transport properties. The optimized membrane achieved near‐ideal monovalent cation selectivity (∼99%), a low area‐specific membrane resistance of 0.06 Ω·m 2 , and an energy conversion efficiency of 45.6%. The same membrane was evaluated over multiple electrochemical testing cycles totaling approximately 300 h, including dedicated 48 h stability measurements under heavy‐metal‐ and organic‐foulant‐containing conditions. A model‐based assessment of a conceptual reverse electrodialysis (RED) stack predicts a 37% increase in power generation, accompanied by an increase in energy conversion efficiency from 30.0% to 41.1%, relative to the commercial‐membrane scenario. These findings demonstrate that regulating interfacial interactions provides an effective design strategy for developing MXene‐based ion‐selective membranes for salinity‐gradient energy harvesting and related electrochemical separation processes.