MX Anti-MXenes from Non-van der Waals Bulks for Electrochemical Applications: The Merit of Metallicity and Active Basal Plane

Abstract

Two-dimensional transition-metal compounds (2DTMCs) are promising materials for electrochemical applications, but 2DTMCs with metallicity and active basal planes are rare. In this work, we proposed a simple and effective strategy to extract 2DTMCs from non-van der Waals bulk materials and established a material library of 79 2DTMCs, which we named as anti-MXenes since they are composed of one M atomic layer sandwiched by two X atomic layers. By means of density functional theory computations, 24 anti-MXenes were confirmed to be thermodynamically, dynamically, mechanically, and thermally stable. The metallicity and active basal plane endow these anti-MXenes with potential as excellent electrode materials, for example, as electrocatalysts for hydrogen evolution reactions (HER). Among the noble-metal free anti-MXenes with favorable H-binding, CuS can boost HER at the whole range of H coverages, while CoSi, FeB, CoB, and CoP show promise for HER at some specific H coverages. The active sites are the tetra-coordinating nonmetal atoms at the basal planes, thus rendering a very high density of active sites for these materials. CoB is also a promising anode material for lithium-ion batteries, showing low Li diffusion energy barriers, a very high capacity, and a suitable open circuit voltage. This work promotes the “computational exfoliation” of 2D materials from non-van der Waals bulks and exemplifies the applications of anti-MXenes in various electrochemical processes.

A strategic review of MXenes as emergent building blocks for future two-dimensional materials: recent progress and perspectives

“…These anti-MXenes are demonstrated as excellent electrode materials for HER activity because of their metallicity and an active basal plane. 234 As shown in Fig. 7c, CoP, CoB, CoSi and FeB exhibit excellent HER at some specific H coverages, while CuS can enhance the HER in the whole range of H coverages, while noble-metal free anti-MXenes show favorable H-binding.…”

“…The choice of surface termination was predicted under varying pH values with different electrode potentials and it was found that the -O terminal group is energetically preferable for Nb 2 C and Nb 4 C 3 , while the mixture of -O and -OH groups is favorable for Ti 2 C, Ti 3 C 2 and V 2 C MXenes. 219 Recently Jinxing et al 234 proposed an effective and simple stratagem for anti-MXenes made of one M atomic layer sandwiched between two X atomic layers (see Fig. 7b).…”

Element‐Doped Mxenes: Mechanism, Synthesis, and Applications

“…The reaction mechanism information can be obtained by simulating these reaction processes, and the intrinsic information such as bandgap, energy, and bond length can be obtained by calculating the electronic structure. [128,[208][209][210] From this information, we can predict the physical and chemical properties of the materials.…”

Cobalt anti-MXenes as Promising Anode Materials for Sodium-ion Batteries

“…In a recent study, 20 Jinxing et al discovered a new class of materials called anti-MXenes, with promising electrochemical and catalytic applications. They studied about 79 anti-MXene materials and found that around 24 anti-MXene materials are stable.…”