Ultrafast,Targeting Fluorion-Capture ElectrochemicalNanosystem Assembled with Polymeraldine Salt-Modulated Ti₃C₂T_<i>x</i> 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_<i>x</i>; PANI = polyaniline) modulated Ti₃C₂T_<i>x</i> MXene electrode as a mediator for electrochemical capture of fluoride ion (F^–) from groundwater. The single-stage configuration equipped with PANI-Cl_<i>x</i>/Ti₃C₂T_<i>x</i> electrode as anode and activated carbon as cathode exhibits an ultrafast removal rate of 4.7 mg-F^– g^–1 min^–1 toward F^– and high selectivity coefficients. Density-functional theory calculations and characterizations reveal that PANI-Cl_<i>x</i>/Ti₃C₂T_<i>x</i> can lower the charge-transfer resistance and activation energy, promoting the synergy of high selectivity of nitrogen-related motifs in PANI-Cl_<i>x</i> and a fast rate of ion intercalation in Ti₃C₂T_<i>x</i>. 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^–1-F^–). Our findings pave the way for the electrochemical production of potable water from fluorine-containing groundwater.