Simultaneous Electrochemical Exfoliation and Covalent Functionalization of MoS<sub>2</sub> Membrane for Ion Sieving
Liang Mei, Zhonglin Cao, Ting Ying, Ruijie Yang, Huarong Peng, Gang Wang, Long Zheng, Ye Chen, Chuyang Y. Tang, Damien Voiry, Haihui Wang, Amir Barati Farimani, Zhiyuan Zeng
Abstract
Abstract Transition metal dichalcogenide membranes exhibit good antiswelling properties but poor water desalination property. Here, a one‐step covalent functionalization of MoS 2 nanosheets for membrane fabrication is reported, which is accomplished by simultaneous exfoliating and grafting the lithium‐ion‐intercalated MoS 2 in organic iodide water solution. The lithium intercalation amount in MoS 2 is optimized so that the quality of the produced 2D nanosheets is improved with homogeneous size distribution. The lamellar MoS 2 membranes are tested in reverse osmosis (RO), and the functionalized MoS 2 membrane exhibits rejection rates of >90% and >80% for various dyes (Rhodamine B, Crystal Violet, Acid Fuchsin, Methyl Orange, and Evans Blue) and NaCl, respectively. The excellent ion‐sieving performance and good water permeability of the functionalized MoS 2 membranes are attributed to the suitable channel widths that are tuned by iodoacetamide. Furthermore, the stability of the functionalized MoS 2 membranes in NaCl and dye solutions is also confirmed by RO tests. Molecular dynamics simulation shows that water molecules tend to form a single layer between the amide‐functionalized MoS 2 layers but a double layer between the ethanol‐functionalized MoS 2 (MoS 2 ‐ethanol) layers, which indicates that a less packed structure of water between the MoS 2 ‐ethanol layers leads to lower hydrodynamic resistance and higher permeation.