Amorphous FePO-anchored three-dimensional macro-porous TiCT 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)-anchored on three-dimensional macro-porous TiCT network (3D FePO@TiCT) electrode is proposed without scarifying TiCT electronic conductivity, wherein sodium-ion captured FePO 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@TiCT//activated carbon (AC) asymmetric CDI device delivered a typical Na-intercalated behavior with high desalination capacity of 65 mg g, 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 with high separator factor up to 6.3 in binary mixture feed of Na and Al. 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.