Theoretical Study on the Electronic Structure and Magnetic Properties Regulation of Janus Structure of M’MCO2 2D MXenes

Mn2C MXene functionalized by oxygen is a semiconducting antiferromagnet and an efficient visible light absorber

Manganese-based MXenes are promising two-dimensional materials due to the broad palette of their magnetic phases and the possibility of experimental preparation because the corresponding MAX phase was already prepared. Here, we systematically investigated geometrical conformers and spin solutions of oxygen-terminated Mn2C MXene and performed subsequent many-body calculations to obtain reliable electronic and optical properties. Allowing energy-lowering using the correct spin ordering via supercell magnetic motifs is essential for the Mn2CO2 system. The stable ground-state Mn2CO2 conformation is antiferromagnetic (AFM) with zigzag lines of up and down spins on Mn atoms. The AFM nature is consistent with the parent MAX phase and even the clean depleted Mn2C sheet. Other magnetic states and geometrical conformations are energetically very close, providing state-switching possibilities in the material. Subsequent many-body GW and Bethe-Salpeter equation (BSE) calculations provide indirect semiconductor characteristics of AFM Mn2CO2 with a fundamental gap of 2.1 eV (and a direct gap of 2.4 eV), the first bright optical transition at 1.3 eV and extremely strongly bound (1.1 eV) first bright exciton. Mn2CO2 absorbs efficiently the whole visible light range and near ultraviolet range (between 10 and 20%).

Janus MXene nanosheets with a strain-induced reversible magnetic state transition for storing information without electricity

The application of strain induces a transition in the ground-state magnetic configuration of Janus TiVC MXene from A-AFM to FM. A new system and method of solid-state disk information storage without electricity is developed based on the as-discovered reversible magnetic state transition in TiVC, which can achieve efficient storage of information in extremely harsh conditions.

Computational studies on functionalized Janus MXenes MM'CT2, (M, M' = Zr, Ti, Hf, M ≠ M'; T = -O, -F, -OH): photoelectronic properties and potential photocatalytic activities

Motivated by the successful synthesis of Janus monolayers of transition metal dichalcogenides (i.e., MoSSe), we computationally investigated the structural, electronic, optical, and transport properties of functionalized Janus MXenes, namely MM'CT2 (M, M' = Zr, Ti, Hf, M ≠ M', T = -O, -F, -OH). The results of the calculations demonstrate that five stable O-terminated Janus MXenes (ZrTiCO2-I, ZrHfCO2-I, ZrHfCO2-III, HfTiCO2-I, and HfTiCO2-III), exhibit modest bandgaps of 1.37-1.94 eV, visible-light absorption (except for ZrHfCO2-I), high carrier mobility, and promising oxidization capability of photoinduced holes. Additionally, their indirect-gap, spatially separated electron-hole pairs, and the dramatic difference between the mobilities of electrons and holes could significantly limit the recombination of photoinduced electron-hole pairs. Our results indicate that the functionalized Janus MXene monolayers are ideal and promising materials for application in visible light-driven photocatalysis.

Editorial for the Special Issue: "Advanced Nanomaterials for Electrochemical Energy Conversion and Storage"

Developing efficient and low-cost energy conversion and storage devices and technologies is all-important issue in order to achieve a low-carbon society, whose performance essentially depends on the properties of materials [...].