Fluorine-Free Fabrication of MXene via Photo-Fenton Approach for Advanced Lithium–Sulfur Batteries

Abstract

The mainstream synthesis method for MXene is using aqueous fluorine-containing acidic solutions to eliminate the A-element layers from their MAX phases. However, this strategy is environmentally hazardous and impairs the material performance (e.g., supercapacitor and Li–S batteries) owing to the presence of ?F terminations. Herein, we exploit a low-temperature “soft chemistry” approach based on photo-Fenton (P.F.) reaction for the fabrication of F-free Ti₃C₂ (Ff-Ti₃C₂) with high purity of 95%. It is confirmed that the continuous generation of highly reactive oxygen species (HO^? and O₂^?– radicals) during the P.F. reaction weakens the metallic Ti–Al bonds in the MAX phase and promotes the formation of high concentration OH^– anions, which are conducive to the sequential topochemical deintercalation of Al layers. Moreover, the strengthened charge accumulation on the Ff-Ti₃C₂ surface creates rich electron “reservoirs” for actuating the Li–S chemistry, which not only strengthens the host–guest interactions but also propels the kinetics of the polysulfide conversion. Taking advantage of the superior mechanical robustness, better electrolyte wettability, and improved electrocatalytic activity, the resultant Ff-Ti₃C₂ can be used as an ideal sulfur host and Li–S chemistry mediator for advanced flexible Li–S batteries.