Interlayer Structure Manipulation of FeOCl/MXene with Soft/Hard Interface Design for Safe Water Production Using Dechlorination Battery Deionization

Suffering from the susceptibility to decomposition, the potential electrochemical application of FeOCl has greatly been hindered. The rational design of the soft-hard material interface can effectively address the challenge of stress concentration and thus decomposition that may occur in the electrodes during charging and discharging. Herein, interlayer structure manipulation of FeOCl/MXene using soft-hard interface design method were conducted for electrochemical dechlorination. FeOCl was encapsulated in Ti₃C₂T_x MXene nanosheets by electrostatic self-assembly layer by layer to form a soft-hard mechanical hierarchical structure, in which Ti₃C₂T_x was used as flexible buffer layers to relieve the huge volume change of FeOCl during Cl⁻ intercalation/deintercalation and constructed a conductive network for fast charge transfer. The CDI dechlorination system of FeOCl/Ti₃C₂T_x delivered outstanding Cl⁻ adsorption capacity (158.47 ± 6.98 mg g⁻¹), rate (6.07 ± 0.35 mg g⁻¹ min⁻¹), and stability (over 94.49 % in 30 cycles), and achieved considerable energy recovery (21.14 ± 0.25 %). The superior dechlorination performance was proved to originate from the Fe²⁺/Fe³⁺ topochemical transformation and the deformation constraint effect of Ti₃C₂T_x on FeOCl. Our interfacial design strategy enables a hard-to-soft integration capacity, which can serve as a universal technology for solving the traditional problem of electrode volume expansion.