Two-Dimensional Janus Transition Metal Oxides and Chalcogenides: Multifunctional Properties for Photocatalysts, Electronics, and Energy Conversion

Abstract

The fast development of high-performance devices for diverse applications requires nanoscale materials with multifunctional properties, motivating theoretical exploration into novel two-dimensional (2D) materials. In this work, we propose a new family of 2D nanomaterials, Janus transition metal oxides and chalcogenides MXY (M = Ti, Zr, or Hf; X = S or Se; Y = O or S; X ≠ Y) monolayers, for their versatile applications. We find that the Janus MXY monolayers are semiconductors with a wide range of band gaps ranging from 0.739 to 2.884 eV. We show that TiSO, ZrSO, and HfSO monolayers are promising candidates for photocatalysis because of their suitable band gaps and optimal redox potentials for water splitting, and ZrSeS and HfSeS monolayers are suitable candidates for nanoscale electronics because of their high carrier mobility. We further show that TiSO, ZrSO, and ZrSeO monolayers possess large piezoelectric properties because of the broken inversion symmetry stemmed from the different atomic sizes and electronegativities of the X and Y elements, which are better or comparable to other 2D and bulk piezoelectric materials. Our study demonstrates that the 2D Janus MXYs may find versatile applications into photocatalysts, electronics, sensors, and energy harvesting/conversion.

Tunable electronic and magnetic properties of monolayer and bilayer Janus Cr2Cl3I3: a first-principles study

“…Janus MoSSe has tunable carrier mobility and obvious Rashba-type spin splitting 11 caused by spin-orbit coupling. 43 And Janus TiSO 44 and MoSSe have suitable band gaps 11 and optical redox potentials for photocatalysis. 11,44,45 The successful synthesis and novel properties of 2D Janus materials could allow them to work as sensors, 44 field-effect transistors, and ultra-sensitive detectors.…”

“…43 And Janus TiSO 44 and MoSSe have suitable band gaps 11 and optical redox potentials for photocatalysis. 11,44,45 The successful synthesis and novel properties of 2D Janus materials could allow them to work as sensors, 44 field-effect transistors, and ultra-sensitive detectors. 46 On the other hand, the successful experimental realization of 2D magnets [21][22][23]27,28,30,35,47 may provide an exciting new platform for the application of low-dimensional spintronics.…”

Janus transition metal dichalcogenides: a superior platform for photocatalytic water splitting

“…This will substantially enhance the light utilization efficiency. Motivated by these beneficial properties, a large number of 2D Janus single layers (SLs) and bilayers (BLs) have been designed for the application of photocatalytic water splitting, such as III 2 XY (III = Ga and In; X, Y = S, Se, and Te, and X ̸ = Y) SLs [7,8], MXY (M = Mo, W) SL and BL [9][10][11][12][13], ScXY SLs [14], PtSSe SL and BL [15], and MXZ (M = Zr, and Hf; X = S and Se; Z = O and S; X ̸ = Z) SLs [16]. Based on the reaction mechanism, photocatalytic water splitting can be divided into four steps (see figure 1(b)): (1) adsorption of water molecules, (2) utilization of sunlight, (3) charge separation and transport, and (4) surface hydrogen evolution reaction (HER) and oxygen evolution reaction (OER).…”

Predicting two-dimensional topological phases in Janus materials by substitutional doping in transition metal dichalcogenide monolayers

“…Despite graphene's popularity, the lack of an electronic bandgap in graphene has driven the interest in 2D TMD films as a promising alternative. 22,23 Recent theoretical [24][25][26][27][28] and experimental [29][30][31][32][33][34][35] studies show that doping is a viable method for enhancing and tuning electronic and optical properties of TMDs for potential applications. One specific type of doping is substitutional doping, and there have been reports of successful experimental substitution of transition metal 29 or chalcogen atoms.…”