Influence of surface termination groups on electrochemical charge storage of MXene electrodes

Abstract

Two-dimensional transition-metal carbides/nitrides (MXenes) have been intensively investigated as electrode materials for electrochemical energy storage devices, such as batteries and supercapacitors, due to their high electronic conductivity and open interlayer spaces. Although MXenes possess various surface termination groups (e.g., –O, –OH, –F, –Cl, and –Br) that directly interact with the accumulated cations to exhibit charge transfer, the influence of each surface termination group on the electrochemical properties of MXene remains elusive. Herein, we report the electrochemical properties of MXenes with controlled surface termination groups. We found that the termination groups play a crucial role in electrochemical reactions in both aqueous and non-aqueous electrolytes.

Prediction of induced magnetism in 2D Ti2C based MXenes by manipulating the mixed surface functionalization and metal substitution computed by xTB model Hamiltonian of the DFTB method

“…3,4,11,25,26 In these structures, the C atoms are still sandwiched between the Ti atoms, and the T atoms on both terminals occupy the top site of bottom titanium on both sides. 3,11,25 We note that previous literature reveals that surface terminal groups such as -Cl, -Br, -I, -S, -Te, -NH, -H, -BrI, and -ClBrI [27][28][29][30][31] were identified in several MXenes too. It was recently predicted that the bare Ti 2 C MXene prefers a magnetic ground state that corresponds to antiferromagnetic (AFM) coupled to ferromagnetic (FM) layers.…”

Structure, Properties, and Preparation of MXene and the Application of Its Composites in Supercapacitors

“…The end groups on the surface of MXene also play a key role in energy storage [37]. Generally speaking, =O functional groups are more stable than -OH and -F because they share more electrons with the M element in the MXene layer, and the conversion between the =O and -OH end groups during charge and discharge processes provides a large number of active sites for redox reactions [38,39]. The unique layered structure of 2D MXene means a larger surface area, and the multi-layered structure is more conducive to ion intercalation and transmission [40].…”

Role of Surface Terminations for Charge Storage of Ti3C2Tx MXene Electrodes in Aqueous Acidic Electrolyte

“…In 2020, a molten salt etching synthetic route was proposed to enrich the variety of MXene surface functional groups, leading to a potentially unlimited number of MXene (MS-MXene) materials with distinct properties. [15] Yamada et al [17] demonstrated that various halogen-terminated MS-MXene prepared using this molten salt route exhibit only poor electrochemical performance in aqueous electrolytes. While our recent research demonstrated a significant enhancement in electrochemical performance in aqueous electrolytes by modifying the surface termination of MS-MXene from Cl-to (N-and O-), [18] it has raised several pivotal questions regarding the influence of surface chemistry (N-vs Cl-terminated MXenes) on MXene's electrochemical kinetics and charge storage mechanism.…”