Accordion-like Multilayered Two-Dimensional Ti₃C₂T_x MXenes for Catalytic Elimination of Organic Dyes from Wastewater via the Fenton Reaction

Two-dimensional (2D) MXenes have attracted tremendous research interest due to their layered structure and exceptional properties. Herein, we have synthesized accordion-like multilayered titanium carbide MXenes (m-Ti3C2Tx) via a single-step HF etching method from titanium aluminum carbide (Ti3AlC2). We demonstrate that the as-grown m-Ti3C2Tx acts as an efficient catalyst for dye degradation through a Fenton reaction in water without requiring any heterostructure due to the presence of a large amount of low-valence Ti states (Ti2+ and Ti3+). Post-growth annealing studies establish the critical roles of Ti2+ and Ti3+ species of m-Ti3C2Tx in dye degradation. Our quantitative analysis reveals a direct correlation between the catalytic efficiency of m-Ti3C2Tx MXene and its Ti2+ content. Under optimum experimental conditions, the degradation efficiency of 100% was achieved from 50 mL of 20 μM concentration methylene blue (MB) solution within 24 min without the need for light illumination. The effect of MB concentration and pH of solutions on the degradation efficiency was investigated, and excellent degradation efficiency was found in acidic as well as basic media, which is significant. Furthermore, the free radical scavenging test indicates that •OH radicals are the main active species involved in this degradation process. We also explored the effect of the nature of dyes on the catalytic degradation efficiency, which reveals that the cationic dye (e.g., rhodamine B) has much higher degradation efficiency than the anionic dye (e.g., methyl orange). This work paves the way for the direct use of 2D MXenes for efficient catalysis without requiring any heterostructure or light illumination, and it provides significant insights for the practical application of m-Ti3C2Tx for polluted water treatment through an advanced oxidation process.