Synthesis by design and application to desalination of VO2/CTAB-Ti3C2 capacitive deionization electrode

•The VO2/CTAB-Ti3C2 heterostructure is prepared via hydrothermal method.•Comparison of the effects of different surfactant treatment on Ti3C2 MXene.•The VO2 nanosheets serves as a support between the MXene layers and makes the MXene structure more stable.•The VO2/CTAB-Ti3C2 heterostructure owns excellent desalination performance. As an emerging technology in capacitive deionization (CDI), flow-electrode capacitive deionization (FCDI) has attracted much attention due to its unlimited electrosorption capacity and continuous operation. Like CDI, carbon is generally chosen as the electrode material for FCDI at this stage, but conventional carbon materials have limited desalination capacity due to the double electric layer. The two-dimensional layered material MXene has been gradually applied to CDI due to its unique structure and physicochemical properties. However, the van der Waals forces exist between the MXene layers, and the layered structure of MXene is susceptible to stacking, while exhibiting an obvious swelling behavior in aqueous solution, thus affecting its desalination performance. Herein, we report a designed VO2/CTAB-Ti3C2 heterostructure synthesised by a simple hydrothermal method. The addition of VO2 can alleviate the lamellar structure buildup of Ti3C2 and improve the desalination performance of Ti3C2. On the other hand, Ti3C2 can be used as a conductive substrate for VO2, which improves the charge transfer rate of VO2, prevents VO2 agglomeration, and provides more contact surfaces for ion intercalation. Compared with the pure VO2 and Ti3C2 electrodes, the composite electrode has a good desalination performance, and its desalination reaches 1041.5 mg g−1 at 1.2 V. Therefore, this VO2/CTAB-Ti3C2 hybrid material is expected to be used as an electrode material for flow capacitive deionization.