Well-dispersed few-layered MoS2 connected with robust 3D conductive architecture for rapid capacitive deionization process and its specific ion selectivity

Capacitive deionization (CDI) has aroused significant concern for its application in treating low-concentration brackish water. However, some carbonaceous materials suffer from the limited salt adsorption capacity (SAC), sluggish adsorption kinetics , and inferior selectivity to particular ions. Hence, we develop the well-dispersed few-layered two-dimensional pseudocapacitive material MoS 2 connected with a robust 3D conductive architecture constructed by carbon nanotubes (CNT) and carbon spheres (CS) (MoS 2 @CNT-CS). The enhanced dispersibility and expanded interlayer of MoS 2 nanosheets provide sufficient faradic effective sites for ion storage and transfer, while the interlaced carbonaceous network affords improved hydrophilicity , convenient electron transport path, and low charge transfer resistance for fast charge transportation and permeation. Therefore, the asymmetric hybrid CDI cell (CNT-CS for anode and MoS 2 @CNT-CS for cathode) delivers a prominent SAC (25.35 mg g −1 ), fast SAR (3.9 mg g −1  min −1 ), enhanced desalination kinetics, and favorable cycling stability. In addition, the specific ion selectivity of MoS 2 @CNT-CS electrode was evaluated systematically in the equimolar multi-salt solutions, and a selectivity order of Ca 2+  > Na +  > Mg 2+  > K + was obtained. The molecular dynamic (MD) calculation provides the lowest intercalation energy for Ca 2+ (−2.55 eV), further confirming the strong interaction and preferable pseudocapacitive deionization of MoS 2 @CNT-CS electrode to Ca 2+ over other cations.