High-Efficiency Water Desalination in Metal Chalcogenide Superlattice via Natural van der Waals Wrapping

Capacitive deionization (CDI) is an emerging technology for seawater desalination. Puckered p-block metal monochalcogenides (MX) are promising candidate materials for electrochemical desalination owing to their high ion removal capacity and layered ion transport channels, yet suffer from chemical instability and strong interlayer coupling induced by M-atom lone-pair electrons, as well as poor conductivity. Here, we introduce a van der Waals (vdW) wrapping strategy using a periodic vdW superlattice to mitigate these limitations. Using (SnS)_1.15TaS₂ superlattice as a proof-of-concept, we demonstrate that alternating SnS and conductive 1H-TaS₂ sublayers enhance structural stability and charge-transfer kinetics during CDI, while maintaining atomically smooth channels for efficient ion transport. Importantly, this architecture intrinsically encapsulates each SnS layer with 1H-TaS₂, dissipating mechanical stresses upon Na⁺ (de)intercalation and ensuring exceptional cycling stability. This design achieves an ultrahigh NaCl removal capacity of 59.6 mg g^-1 (500 mg L^-1 NaCl, 1.2 V), surpassing SnS and TaS₂ alone by factors of 136.5% and 100%. The desalination performance of (SnS)_1.15TaS₂ ranks among the best of reported 2D electrode materials. The electrode exhibits an excellent desalination rate of 8.7 mg g^-1 min^-1, and >85% capacity retention over cycling tests. The vdW wrapping strategy establishes a robust design paradigm for high-performance desalination electrodes.