A lamellar chitosan-lignosulfonate/MXene nanocomposite as binder-free electrode for high-performance capacitive deionization

Ti3C2Tx (MXene) is considered as a superior electrode material for capacitive deionization (CDI) due to its high conductivity and two-dimensional structure. However, the electrochemical performance of pristine MXene nanosheets has been significantly impeded by the surface oxidation in the aqueous media and re-stacking caused by van der Waals forces which reduces the ions storage capacity. In this study, the chitosan-lignosulfonate/MXene (CLM) composite was used as a binder-free electrode to enhance the ion storage capacity and long-run cycling stability for hybrid capacitive deionization (HCDI). The chitosan-lignosulfonate nanospheres were able to increase the interlayer spacing between the MXene nanosheets effectively, which has significantly enhanced the ion storage capacity and electrochemical properties of the electrode. The binder-free CLM cathode demonstrated a high salt adsorption capacity of 44.6 mg g−1 and a maximum average salt adsorption rate of 5.8 mg g−1 min−1 at 1.2 V. A high cycling stability above 97 % for 30 cycles was observed. Also, the long-term stability of CLM electrode was studied by X-ray photoelectron spectroscopy (XPS) and the results showed that the CLM electrode was not prone to surface oxidation after 30 cycles. This study can guide future development of high-performance 2D material composite electrodes for enhancing capacitive deionization efficiency.