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.