The Study On Enhanced Ion Transport Behavior Based On Mg²⁺ Pre-Intercalation Into Nanochannels Of MXene

MXene membranes,as typical two-dimensional transition metal carbide,with unique two-dimensional nanoscale layered structure have received extensive attentions,in the fields of energy storage and water purification due to their rich functional groups on the surface and easy modification.In the fields of energy storage and water purification,the unique interaction mechanism of Mg²⁺with other ions,and channel’s surface within two-dimensional nanochannels of MXene has not been deeply explored yet.In this thesis,after obtaining MXene films with a thickness of～2.5μm by vacuum-assisted filtration,the ion transport rates of the original MXene films were tested using H-tubes,and the relevant transport rates were measured by transport rates corresponding to K⁺,Na⁺,Li⁺,Ca²⁺,and Mg²⁺in MXene films,as 1.3,3.27,2.015,2.46,and 4.58×10^-3mmol L^-1min^-1,respectively.The results revealed the variability of ion transport rates of MXene films for different ions,and the variability of ion transport rates of MXene films for different ions.By testing the ion transport rates of 2D MXene membranes in different ion solutions(Li⁺,Na⁺,K⁺,Ca²⁺,Mg²⁺)before and after pre-intercalation using H-tubes,we found that the ion transport rates are significantly increased due to the pre-intercalation of Mg²⁺.Especially for Li⁺transport,the enhancement reached268.49%.Through the X-ray diffraction（XRD）characteraization,it was found that the pre-intercalation of Mg²⁺significantly increased the layer spacing of 2D MXene nanochannels.Based on these results,Energy dispersive spectrometer（EDS）and X-ray photoelectron spectroscopy（XPS）characterizations are employed to investigate the two-dimensional MXene film with Mg²⁺pre-intercalated layers（Mg-Ti₃C₂T_x）.The obtained EDS spectra demonstrated the effective intercalation of Mg²⁺in the 2D MXene film,and in XPS spectra,the peak at 1305 e V of Mg 1s proved that Mg²⁺did not form any valence bond with the surface of MXene 2D nanochannels and existed alone in the 2D nanochannels.It was also found that the ratio of-OH functional groups on the surface of MXene films changed after a long period of Mg²⁺and Li⁺transport,with Mg²⁺increasing the content of-OH functional groups in the channels and Li⁺decreasing the content of-OH functional groups when entering the two-dimensional nanochannels.Ultraviolet photo-electron spectroscopy（UPS）results showed an increase in the work function of 2D nanochannel after Mg²⁺pre-intercalation（4.11 e V）,compared with Li⁺transport（4.07 e V）,demonstrating that the Mg²⁺pre-intercalation reduces the interaction of other metal ions with the channel.To confirm the stronger interaction of Mg²⁺with MXene,the Zeta potentials of MXene solution with different concentrations of Mg²⁺were measured.The enhancement of ion transport rate by Mg²⁺is mainly contributed from the fact that Mg²⁺intercalation increases the layer spacing of MXene membrane as a channel support between layers,while Mg²⁺increases the work function of MXene two-dimensional nanochannels,decreasing the interaction of other ions with the channel’s surface.