Engineered molybdenum disulfide-based nanomaterials for capacitive deionization applications

Abstract

Capacitive deionization (CDI) is a highly promising technique used for the removal of ions from water, showing great potential in the desalination of salty water and wastewater remediation. CDI has the advantages of energy efficiency, simple operation, excellent reversibility, long-term stability, and high feasibility for coupling with other techniques. Similar to supercapacitors, the electrode materials play a crucial role in determining the CDI performance, such as operating voltage, desalination capacity, and lifecycle of CDI cells. Molybdenum disulfide (MoS₂), a typical two-dimensional (2D) metal sulfide, has gained tremendous attention in the CDI technique due to its exceptional mechanical, electrical, and optical properties. Herein, we critically discuss the inventory and recent progress in the rational design of MoS₂-based electrodes for CDI cells. Initially, we present a brief introduction on the foundation knowledge of CDI systems and the structure of MoS₂. For a comprehensive review, we summarize the common techniques employed to prepare MoS₂-based nanomaterials, ranging from various exfoliation processes to chemical vapor deposition, colloidal synthesis, hydrothermal/solvothermal synthesis, and molten salt synthesis. Significantly, the recent progress in MoS₂-based electrodes for application in CDI is summarized in detail. These systems are divided into pristine MoS₂ and various MoS₂-based composites with other species, such as carbon, conducting polymers, metal oxides, MXenes, and C₃N₄. Finally, to aid in the further development of MoS₂ electrodes for efficient and long-term stable CDI, some challenges and possible solutions are outlined.