Dual-ion electrochemical deionization system based on binder-free Bi2O3@MXene-Bi@MXene electrodes

Dual-ion electrochemical deionization (DEDI) system is a promising strategy for increasing the performance of capacitive deionization (CDI). We presented a simple strategy to simultaneously prepare chloride and sodium ion storage film electrode by combing MXene with Bi2O3. The sandwich-like three-dimensional (3D) structure Bi2O3@MXene film electrode can well storage sodium ions by intercalation reaction. Interestingly, the Bi@MXene film electrode can be prepared from Bi2O3@MXene film simply by reducing Bi2O3 to Bi, which can capture chloride ions by the electrochemical reaction of Bi and BiOCl. The MXene provides outstanding conductivity and flexibility for the composite film electrodes, and the introducing of Bi2O3 limits the re-stacking of MXene nanosheets while the Bi enhances the chloride ions adsorption of MXene by conversion reaction. When assembled as a DEDI device, it obtained a high desalination capacity of 86.8 mg/g at the current of 20 mA/g, and the fastest desalination rate of 3.21 mg/g/min under the current of 200 mA/g. Moreover, a strong power source built by two DEDI devices in series can drive an LED more than 5 min during the regeneration process. Such a simple and effective strategy can promote the development of binder-free electrode DEDI system.