Probing the synergistic effects of amino compounds in mitigating oxidation in 2D Ti3C2Tx MXene nanosheets in aqueous environments†

Abstract

The shelf life of 2D MXenes in functional devices and colloidal dispersions is compromised due to oxidation in the aqueous system. Herein, a systematic investigation was carried out to explore the potential of various amino compounds as antioxidants for Ti₃C₂T_x MXenes. A range of basic, acidic, and neutral amino acids were examined for their effectiveness, where certain antioxidants failed to protect MXenes from oxidation, while others accelerated their decomposition. Serine, threonine, and asparagine demonstrated excellent antioxidant activity, likely due to their evenly distributed molecular charges. These neutral amino acids outperformed glutamic acid, which possesses an electron-withdrawing COOH group, and lysine, with an electron-donating NH₂ group. Serine-functionalized MXene realized a stabilization time constant reaching 128 days, as determined by first-order reaction kinetics. Additionally, when employed as supercapacitor electrodes, aged MXene and serine-functionalized MXene exhibited specific capacitance values of 219.2 and 280.3 F g⁻¹ at 5 A g⁻¹ after 6 weeks, respectively. This work addresses the gap in the practical work on ionic stabilization of 2D MXenes and has significant implications for the long-term colloidal storage of MXenes using greener chemicals.