Toward understanded the electrochemical capacitance mechanism of MXene by intercalation of inorganic ions and organic macromolecular ions

doi:10.1016/j.apsusc.2021.152030

Applied Surface Science

Volume 578, 15 March 2022, 152030

https://doi.org/10.1016/j.apsusc.2021.152030 Get rights and content

Highlights

•
MXene-NaCl and MXene-CTAB by ion ultrasonic intercalation were synthesized.
•
The intercalation of macromolecular ions CTA⁺ improves the electrochemical reaction activity.
•
MXene-CTAB has a redox reaction and adsorbs the counter-ions in the electrolyte.

Abstract

Interlayer ion modification of MXene is one of the effective ways to improve the pseudocapacitance performance. However, the origin of electrochemical capacitance mechanism still remains elusive due to the effect of different kinds of ion interlayer modification. In this work, interlayer modification of MXene (Ti₃C₂Cl₂) with inorganic ions (NaCl) and organic macromolecular ions (cetyl trimethyl ammonium bromide cation, CTAB) were carried out by ion ultrasonic intercalation and the electrochemical capacitance mechanism was investigated. It was found that MXene- CTAB has higher specific capacitance (258.28F g⁻¹ Vs 225.55F g⁻¹) and better cycle stability (93% retention Vs 85% retention after 3000 cycles) than MXene-NaCl. Such a large difference in electrochemical energy storage performance is mainly due to two points : (1) Organic macromolecular CTAB can effectively expand the layer spacing of MXene, which is conducive to the storage of electrolyte ions. (2) Compared with inorganic ions, organic macromolecular ions not only have redox reaction with interlayer ions of MXene, but also can adsorb counter ions in the electrolyte, thus providing additional pseudocapacitance. This work opens up a new way for the development of high-performance MXene based electrode materials.

Graphical abstract

Interlayer modification of MXene (Ti₃C₂Cl₂) with inorganic ions (NaCl) and organic macromolecular ions (CTAB) were carried out by ion ultrasonic intercalation. The specific capacitance of MXene-CTAB in (NH₄)₂SO₄ electrolyte is 258.28F g⁻¹, which is higher than that of MXene-NaCl which is 225.55F g⁻¹. In-situ electrochemical XRD and in-situ electrochemical Raman spectroscopy reveal the electrochemical capacitance mechanisms.

Introduction

As a two-dimensional material, MXene has incredible development potential in the field of supercapacitors since its discovery in 2011 [1], [2], [3]. MXene is usually prepared by etching the corresponding MAX with a fluorine-containing strong acid solution [4], [5]. In order to make the preparation of MXene more environmentally friendly, it is feasible to corrode MAX by Lewis acid [6], [7]. MXene is reported to have a flexible interlamellar spacing that can accommodate ions at high charge and discharge rates [8], [9], [10].However, MXene nanosheets are prone to aggregate and self-weight accumulate, which limits the accessibility of electrolyte ions and significantly reduces the electrochemical availability and intrinsic properties of MXene nanosheets [11].

The reversible insertion of cations and small organic molecules into MXene layers is an effective method to overcome the above problems. Han et al. inserted tetramethylammonium hydroxide (TMAOH) into multilayer MXene through hydrothermal process, in which TMAOH can diffuse and intercalate to promote the subsequent delamination [12]. Li et al. removed the end group by calcining after K⁺ intercalation, which significantly increased the capacitance of MXene [13]. After that, Al-Temimy et al. proved by characterizing the electronic structure of Ti₃C₂T_x after intercalation that cationic intercalation can expand the layer spacing and significantly change the surface chemistry of Ti₃C₂T_x [14]. Although it has been reported that interlayer modification can further improve the electrochemical performance, the relationship of interlayer modification between inorganic ions and organic macromolecular ions and the energy storage mechanism are not clear.

Herein, in order to investigate the electrochemical capacitance mechanism of MXene during ion insertion with different properties, the MXene (Ti₃C₂Cl₂) was modified respectively by inorganic ion Na⁺ and organic macromolecular ion CTA⁺, based on cationic intercalation. As a result, MXene-CTAB in (NH₄)₂SO₄ electrolyte has the highest specific capacitance which is 258.28F g⁻¹ when the current density is 0.5 A g⁻¹. When the power density is 200 W kg⁻¹, the maximum energy density of MXene-CTAB is 11.48 Wh K g⁻¹. Compared with MXene-CTAB under the same condition, the specific capacitance and energy density of MXene-NaCl are only 225.55F g⁻¹ and 10.02 Wh K g⁻¹. In addition, MXene-CTAB has better cycle stability, and the capacitance retention rate is about 100% after 2500 cycles at a current density of 1.0 A g⁻¹. The intercalation of CTA⁺ increases the interlayer spacing of MXene and improves the electrochemical reaction activity. In addition, CTA⁺ in MXene-CTAB not only has a redox reaction with interlayer ions of MXene, but also adsorbs counter-ions in electrolyte, making MXene-CTAB has better electrochemical performance than MXene-NaCl.

Section snippets

Materials

MAX phase (Ti₃AlC₂) powders and Cadmium Chloride (CdCl₂) were derived from Aladdin Chemical Reagent Company. Xi’an Keluo Chemical Reagent Co., Ltd provided sodium chloride (NaCl), Hexadecyl trimethyl ammonium Bromide (CTAB, C₁₉H₄₂BrN), sulfuric acid (H₂SO₄), N, N-Dimethylformamide (DMF, C₃H₇NO).

Synthesis of MXene (Ti₃C₂Cl₂)

Ti₃AlC₂ powders were mixed with CdCl₂ salt in 1:8 M ratio using an agate mortar. The resultant mixture was laid in a quartz boat and placed in a vacuum tube furnace which was heated to 610 ℃ in argon

Results and discussions

Fig. 1(a) indicates that MXene (Ti₃C₂Cl₂) was obtained by etching MAX phase according to salt etching method, and then obtained MXene-NaCl by intercalation of inorganic ion Na⁺ and MXene-CTAB obtained by intercalation of organic ion CTA⁺. The morphologies of samples were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). SEM and TEM of MAX phase and MXene (Ti₃C₂Cl₂) are shown in Fig. S1(a-f) (supporting information). Fig. 1(b,c) and Fig. 1(e,f) show

Conclusions

In summary, we used inorganic ions (NaCl) and organic macromolecular ions (CTAB) to intercalate MXene (Ti₃C₂Cl₂) and investigate the difference of layer spacing and electrochemical performance between MXene-NaCl and MXene-CTAB. The results show that the organic macromolecule CTAB can enlarge the layer spacing of MXene (Ti₃C₂Cl₂) to a greater extent than NaCl (The layer spacing of MXene-CTAB is about 1.16 nm and MXene-NaCl is about 1.14 nm). The specific capacitance of MXene-CTAB in (NH₄)₂SO₄

CRediT authorship contribution statement

Yuxuan Zhang: Methodology, Data curation, Software, Writing – original draft, Visualization, Validation, Writing – review & editing, Investigation. Zhilin Zhao: Methodology, Investigation, Data curation, Validation, Writing – review & editing. Chunyan Luo: Investigation, Validation. Xinming Wu: Methodology, Investigation, Validation, Writing – review & editing. Weixing Chen: Investigation, Validation.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgment

This work was supported by National Natural Science Foundation of China (21975196) and Natural Science Foundation of Shaanxi Province of China (2021JM-431).

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Short CommunicationToward understanded the electrochemical capacitance mechanism of MXene by intercalation of inorganic ions and organic macromolecular ions

Highlights

Abstract

Graphical abstract

Introduction

Section snippets

Materials

Synthesis of MXene (Ti3C2Cl2)

Results and discussions

Conclusions

CRediT authorship contribution statement

Declaration of Competing Interest

Acknowledgment

Electric Field Effect in Atomically Thin Carbon Films

Science

MXenes for Rechargeable Batteries Beyond the Lithium-Ion

Adv. Mater.

Two-Dimensional Nanocrystals: Two-Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2

Adv. Mater.

25th Anniversary Article: MXenes: a New Family of Two-Dimensional Materials

Adv. Mater.

Synthesis and Characterization of Two-Dimensional Nb4C3 (MXene)

Chem. Commun.

Covalent Surface Modifi-cations and Superconductivity of Two-dimensional Metal Carbide MXenes

Science

A general Lewis Acidic Etching Route for Preparing MXenes with Enhanced Electrochemical Performance in Non-Aqueous Electrolyte

Nat. Mater.

Atomic-Scale Clarification of Structural Transition of MoS2 upon Sodium Intercalation

ACS Nano

Short Communication
Toward understanded the electrochemical capacitance mechanism of MXene by intercalation of inorganic ions and organic macromolecular ions

Synthesis of MXene (Ti₃C₂Cl₂)

Two-Dimensional Nanocrystals: Two-Dimensional Nanocrystals Produced by Exfoliation of Ti₃AlC₂

Synthesis and Characterization of Two-Dimensional Nb₄C₃ (MXene)

Atomic-Scale Clarification of Structural Transition of MoS₂ upon Sodium Intercalation