Achieving Exceptional Volumetric Desalination Capacity Using Compact MoS2 Nanolaminates

Abstract

Capacitive deionization (CDI) has emerged as a promising technology for freshwater recovery from low-salinity brackish water. It is still inapplicable in specific scenarios (e.g., households, islands, or offshore platforms) due to too low volumetric adsorption capacities. In this study, a high-density semi-metallic molybdenum disulfide (1T'-MoS₂) electrode with compact architecture obtained by restacking of exfoliated nanosheets, which achieve high capacitance up to ≈277.5 F cm^-3 under an ultrahigh scan rate of 1000 mV s^-1 with a lower charge-transfer resistance and nearly tenfold higher electrochemical active surface area than the 2H-MoS₂ electrode, is reported. Furthermore, 1T'-MoS₂ electrode demonstrates exceptional volumetric desalination capacity of 65.1 mg_NaCl cm^-3 in CDI experiments. Ex situ X-ray diffraction (XRD) reveal that the cation storage mechanism with the dynamic expansion of 1T'-MoS₂ interlayer to accommodate cations such as Na⁺, K⁺, Ca²⁺, and Mg²⁺, which in turn enhances the capacity. Theoretical analysis unveils that 1T' phase is thermodynamically preferable over 2H phase, the ion hydration and channel confinement also play critical role in enhancing ion adsorption. Overall, this work provides a new method to design compact 2D-layered nanolaminates with high-volumetric performance for CDI desalination.

Keywords: 2D materials; capacitive deioniazation; electrochemical intercalation and exfoliation; exceptional volumetric capacity; nanolaminate membranes.