Surface Functional Groups and Electrochemical Behavior in Dimethyl Sulfoxide‐Delaminated Ti₃C₂T_x MXene

Abstract

Functional groups in two-dimensional (2D) Ti C T MXene are an important factor influencing electrochemical performance in many applications involving energy storage, electrochemical sensors, and water purification. However, after dimethyl sulfoxide (DMSO) delamination, the effect of surface functionalities in Ti C T is still unclear and there are no systematic reports on its capacitive behavior. Experiments and theoretical calculations confirm the relationship between different surface functionalities, the DMSO delamination effect, and the electrochemical behavior of the DMSO-delaminated Ti C T . The dominant -O and -OH terminations are attributed for surfaces delaminated by using HF [Ti C T (HF)] and LiF/HCl [Ti C T (LiF/HCl)], respectively. Theoretical results are also in agreement with experimental results in that -OH terminations are essential for the formation of a free-standing film. Compared to non-delaminated Ti C T (HF) (similar O/F ratios of 1.37 and 1.42), there is a significant DMSO delamination effect for Ti C T (LiF/HCl) because of different O/F ratios of 2.9 and 3.6. Additionally, the delaminated Ti C T (LiF/HCl) electrodes deliver a higher capacitance of 508 F cm than that of 333 F cm for the delaminated Ti C T (HF), although it exhibited lower equivalent series resistance, lower interlayer spacing, and slightly lower specific surface area. This study provides direct and systematic experimental evidence for different functional groups in Ti C T MXene based on the DMSO delamination effect.

Two‐Dimensional Transition Metal Carbides and Nitrides (MXenes): Synthesis, Properties, and Electrochemical Energy Storage Applications

“…Based on the neutron scattering measurements of Ti 3 C 2 T x , it is pointed out that interlayer interactions can be described by hydrogen bonding between O or F groups of one side of nanosheet and the ‐OH surface groups of the opposing side, and van der Waals bonding of O and/or F atoms between the sheets . The strength of interlayer hydrogen bonding depends on the orientation of the ‐OH groups relative to the layers and the amount of ‐OH relative to the ‐O and ‐F moieties positioned on the opposing surface . When water molecules are present between the layers, the hydrogen bonds form on the sheet surfaces.…”

Enhancing Capacitance Performance of Ti3C2Tx MXene as Electrode Materials of Supercapacitor: From Controlled Preparation to Composite Structure Construction

“…At present, there are many methods for accelerating the exfoliation of materials, including: (1) mechanical methods: Feng et al [56] showed the ultrasonic treatment-assisted exfoliating process could inhibit the formation of a stable force between layers to obtain Ti 3 C 2 T x sheets with rich functional groups on the surface, but also cause the problem of a small lateral dimension. (2) The introduction of repulsion groups: Qian et al [61] revealed that the repulsion between the methyl group of dimethyl sulfoxide (DMSO) organic intercalant and the hydroxyl group on the surface of Ti 3 C 2 T x contributes to increase the interlayer spacing. Meanwhile, -F is replaced partly by a hydroxyl group during the exfoliating, leaving the high boiling organic reagent [62].…”

Enhancing the conductivity, stability and flexibility of Ti3C2Tx MXenes by regulating etching conditions

“…From the XPS Ti2p region (Fig. 2d), the binding energies of approximately 455, 456, 458 and 569 eV were assigned to Ti2p 3/2 for Ti-C bond, Ti (Ⅱ), Ti (III) and Ti (IV)-O bond respectively, and the binding energies above 460 eV presented the corresponding peaks of Ti2p 1/2 electron orbit [38][39]. Obviously, Ti (IV)-O bond was much stronger in TM-Ti 3 C 2 T x than the other two samples and was absent in HF-Ti 3 C 2 T x , which well identified the results of the Raman analysis.…”