Amorphous FePO4-anchored three-dimensional macro-porous Ti3C2Tx for superior capacitive deionization and sodium-ion selectivity

Faradaic capacitive deionization (CDI), which exploits pseudo-capacitive electrodes, is an appealing water-purification candidate from low-salinity desalinated water due to its fast Faradaic electro-sorption and ion intercalations. However, current Faradaic CDI faces the challenge in low salt adsorption capacity and poor selective sodium-ion (Na + ) applicability. Herein, amorphous ferric phosphate (FePO 4 )-anchored on three-dimensional macro-porous Ti 3 C 2 T x network (3D FePO 4 @Ti 3 C 2 T x ) electrode is proposed without scarifying Ti 3 C 2 T x electronic conductivity, wherein sodium-ion captured FePO 4 provided abundant Na + adsorption site for enhancing desalination capacity and Na + selectivity. Simultaneously, highly-interconnected channels accelerated electron/ion transport to enable effective Na + intercalation in electro-sorption. Accordingly, the assembled FePO 4 @Ti 3 C 2 T x //activated carbon (AC) asymmetric CDI device delivered a typical Na + -intercalated behavior with high desalination capacity of 65 mg g −1 , in which electric current generation could power a blue light-emitting diode (LED) screen. Importantly, the asymmetric CDI device enabled an evident Na + selectivity over the Al 3+ with high separator factor up to 6.3 in binary mixture feed of Na + and Al 3+ . This study offers a new idea to achieve high desalination performance and sodium-ion selectivity via 3D framework supported ions-capture structure in seawater desalination.