Facile fabrication of intercalation-type pseudocapacitive S-Ti₃C₂T_x/PANI/F-Ti₃C₂T_x cathode for asymmetric capacitive deionization

Although tremendous efforts have been paid on Ti₃C₂T_x as a cathode for capacitive deionization (CDI), its structural instability and easy agglomeration have always limited such a promising application. In this study, a hybrid of hollow Ti₃C₂T_x spheres and flakes was synchronously fabricated by a novel sacrificial-templated method for the first time, and then immobilized/bonded together by in-situ polymerization of polyaniline, which was labelled as S-Ti₃C₂T_x/PANI/F-Ti₃C₂T_x. The highest specific capacitance of S-Ti₃C₂T_x/PANI/F-Ti₃C₂T_x in 1 M NaCl solution was measured to be 102 F·g⁻¹, and diffusion capacitance of the as-obtained S-Ti₃C₂T_x/PANI/F-Ti₃C₂T_x was calculated to be 63%. Thus, a high salt adsorption capacity of 76 mg·g⁻¹ with a maximum salt adsorption rate of 11.45 mg·g⁻¹·min⁻¹ was obtained, which is much higher than that of Ti₃C₂T_x-related materials in literature for asymmetric CDI system. Moreover, such a superior desalination performance was verified stable at almost 100% after 30 cycles. Besides the ion intercalation and fluoro/hydroxyl groups of Ti₃C₂T_x, the high performance and stability of the as-obtained S-Ti₃C₂T_x/PANI/F-Ti₃C₂T_x should also be ascribed to the beneficial effects of immobilization/bonding role of conductive PANI between S-Ti₃C₂T_x and F-Ti₃C₂T_x. This study gives a new perspective to promote the real applications of CDI by designing highly capacitive and stable electrode materials.