Electrochemical investigation of interfacial properties of Ti₃C₂T_x MXene modified by aryldiazonium betaine derivatives

MXene was modified by aryldiazonium betaine derivatives terminated either in a sulfo (SB) or a carboxy (CB). Since MXene contains free electrons, betaine derivatives could be grafted to MXene spontaneously. Kinetics of spontaneous grafting of SB and CB towards MXene was electrochemically examined in two different ways and experiments confirmed quicker spontaneous SB grafting compared to CB. Electrochemical methods investigating non-Faradaic and Faradaic redox behaviour with contact angle measurements and secondary ion mass spectrometry confirmed differences in formation and interfacial presentation of betaine layers spontaneously grafted on MXene. Electrochemical grafting by a redox trigger provides denser layer of SB and CB on the interface compared to spontaneous. Electrochemically grafted SB layer offers much lower interfacial resistance and electrochemically active surface area compared to electrochemically grafted CB layer. By adjusting SB/CB ratio in the solution during electrochemical grafting it is possible to effectively tune redox behaviour of MXene modified interface. (authors)