Ultrafast, Targeting Fluorion-Capture Electrochemical Nanosystem Assembled with Polymeraldine Salt-Modulated TiCT MXene.

Fluoride-containing groundwater has become a major concern since it serves as a source of drinking water for over half the world's population. Here, we develop an ion-selective polymeraldine salt (PANI-Cl; PANI = polyaniline) modulated TiCT MXene electrode as a mediator for electrochemical capture of fluoride ion (F) from groundwater. The single-stage configuration equipped with PANI-Cl/TiCT electrode as anode and activated carbon as cathode exhibits an ultrafast removal rate of 4.7 mg-F g min toward F and high selectivity coefficients. Density-functional theory calculations and characterizations reveal that PANI-Cl/TiCT can lower the charge-transfer resistance and activation energy, promoting the synergy of high selectivity of nitrogen-related motifs in PANI-Cl and a fast rate of ion intercalation in TiCT. A stack-based multi-stage configuration operated at a staircase descent voltage mode is applied to produce freshwater from practical groundwater with low energy consumption (0.92 kWh kg-F). Our findings pave the way for the electrochemical production of potable water from fluorine-containing groundwater.