Enhancing both the long-term stability and methylene blue adsorption performance of TiVCT _x via a facile antioxidation treatment

MXenes are widely recognized as excellent dye adsorption materials. However, their propensity to oxidize will greatly reduce their stability and performance. In the present work, a simple antioxidation treatment was applied to TiVCT_x using three acid antioxidants (oxalic acid (OA), sodium citrate (SC), and tartaric acid (TA)) and their effects on the stability and methylene blue adsorption performance were investigated. The stability of TiVCT_x stored in an aqueous solution within 14 days was assessed using XRD and XPS. The antioxidant-treated TiVCT_x showed a significant improvement in both long-term stability and MB adsorption properties, with TA-TiVCT_x demonstrating the best performance. The MB adsorption of the as-prepared TiVCT_x was physical and multilayer, but it became a multilayer process where physical and chemical adsorptions coexist after antioxidation treatment. The maximum adsorption capacity of TA-TiVCT_x reached 8061.03 mg g^-1 and remained at 3887.28 mg g^-1 after 14 days of storage, far exceeding the performance of other reported adsorbents. It is found that the enhanced stability is attributed to the dense protective layer formed by the chelation between the antioxidant and TiVCT_x, and the improved MB adsorption performance is ascribed to the synergistic effect of electrostatic adsorption between TiVCT_x and MB and the Bloch reaction between the antioxidants and the MB molecules. The differences in the enhancement effects of the various antioxidants are related to the number of carboxyl and hydroxyl groups in the antioxidant molecules. This work provides useful reference and guidance for obtaining MXenes with better stability and adsorption performance.