Imparting dispersibility and electrochemical activity to chlorine-terminated MXenes via oxygen enrichment

Chlorine-terminated Ti₃C₂ MXenes (Cl-MXenes) demonstrate remarkable resistance to water- and oxygen-induced degradation, yet their hydrophobic nature limits compatibility with polar solvents. This is a stark contrast to the hydrophilic, oxygen-terminated MXenes produced through conventional fluoride-based etching. Capitalizing on the labile character of surface chlorine atoms, we developed a solution-based approach to create oxygen-enriched Cl-MXenes (O,Cl-MXenes) through delamination in alkaline dimethyl sulfoxide. This controlled functionalization yields mixed chlorine-oxygen terminations (a ∼95% increase in the Ti–O/Ti–Cl ratio), substantially improving MXene dispersibility in organic solvents. Oxygen enrichment through direct addition at the Ti surface and partial chlorine substitution not only enhances dispersion stability and oxidation resistance (up to ∼10 days) but also combines the anodic stability (+∼0.2 V) of chlorine terminations with the high capacitive activity of oxygen groups. These results establish that co-functionalization with chlorine and oxygen produces MXenes with enhanced solution processability and environmental stability, offering a versatile materials design strategy for advancing MXene-based technologies.