Binder-free Bi@MXene film with 3D sandwich structure for highly hybrid capacitive deionization

Abstract

Developing anode materials significantly enhances the desalination performance of hybrid capacitive deionization (HCDI). Bismuth exhibits high selectivity for chloride ion removal. However, the sluggish kinetics and poor cycling stability of bismuth present considerable challenges for its application in high-capacitance deionization. In this study, we successfully prepared a binder-free Bi@MXene film electrode for chloride storage by employing an electrostatic self-assembly strategy to anchor Bi nanospheres into MXene layers. The bismuth nanospheres, as the pillars of MXene network, improve the self-stacking problem of Ti₃C₂T_X layers. And MXene layers effectively mitigate the volume expansion of bismuth nanospheres through the spatial confinement effect. Benefiting from three-dimentional sandwich structure of Bi@MXene film, the HCDI system exhibits outstanding salt adsorption capacity (113.4 mg·g⁻¹), excellent adsorption rate (4.2 mg·g⁻¹·min⁻¹) and a good desalination capacity retention of 84.6 % following 50 cycles at 100 mA·g⁻¹. The development of this composite material provides insights for the design of efficient and stable chloride storage electrodes.