Enhanced capacitive deionization by rGO@PEI/MoS2 nanocomposites with rich heterostructures

Abstract

Heterostructure electrodes prepared from the nanocomposite rGO/MoS2 have become one of the hot spots for capacitive deionization (CDI) research due to their excellent electrochemical properties. However, during the preparation process, the electrostatic repulsion by the electronegativity of graphene oxide (GO) and MoS2 precursor (molybdate ion) led to the undesirable combination of rGO and MoS2. Only a small amount of MoS2 existed on the surface of rGO, which was not conducive to the formation of heterostructures between rGO and MoS2. In this work, GO was modified by the positively charged polyethyleneimine (PEI), forming the GO@PEI with positively charged surfaces. Due to the electrostaticinteraction with the precursors (Molybdate ions) of MoS2, the rGO@PEI/MoS2 composites with rich heterostructures were successfully prepared. As result, the rGO@PEI/MoS2 composites exhibited high specific capacitance, excellent cycle stability, and enhanced desalination performance. The rGO@PEI/MoS2 had a maximum specific capacitance of 212.53F/g, which was a 45% improvement over rGO/MoS2. The maximum electro-adsorption of the rGO@PEI/MoS2 electrode was about 24.13 mg/g with pole plate spacing of 1 mm at 1.0 V. The excellent electrochemical properties and desalination capability of the rGO@PEI/MoS2 composite were attributed to the synergistic effect generated by the rich heterostructure. The rich heterostructure formed between rGO and MoS2 through van der Waals forces and chemical bonding (Mo-N-C) perfectly combined their advantages and counteracted their disadvantages.