Rolling the WSSe Bilayer into Double-Walled Nanotube for the Enhanced Photocatalytic Water-Splitting Performance

For the emerging Janus transition metal dichalcogenides (TMD) layered water-splitting photocatalysts, stacking the monolayers to form bilayers has been predicted to be an effective way to improve their photocatalytic performances. To achieve this, the stacking pattern plays an important role. In this work, by means of the density functional theory calculations, we comprehensively estimate energetical stability, light absorption and redox capacity of Janus WSSe bilayer with different stacking patterns. Unfortunately, the Janus WSSe bilayer with the most stable configuration recover the out-of-plane symmetry, which is not in favor of the photocatalytic reactions. However, rolling the Janus WSSe bilayer into double-walled nanotube could stabilize the appropriate stacking pattern with an enhanced instinct dipole moment. Moreover, the suitable band edge positions, high visible light absorbance, outstanding solar-to-hydrogen efficiency (up to 28.48%), and superior carrier separation promise the Janus WSSe double-walled nanotube the potential for the photocatalytic water-splitting application. Our studies not only predict an ideal water-splitting photocatalyst, but also propose an effective way to improve the photocatalytic performances of Janus layered materials.

Strain Engineering on the Electronic and Optical Properties of WSSe Bilayer

Controllable optical properties are important for optoelectronic applications. Based on the unique properties and potential applications of two-dimensional Janus WSSe, we systematically investigate the strain-modulated electronic and optical properties of WSSe bilayer through the first-principle calculations. The preferred stacking configurations and chalcogen orders are determined by the binding energies. The bandgap of all the stable structures are found sensitive to the external stress and could be tailored from semiconductor to metallicity under appropriate compressive strains. Atomic orbital projected energy bands reveal a positive correlation between the degeneracy and the structural symmetry, which explains the bandgap evolutions. Dipole transition preference is tuned by the biaxial strain. A controllable transformation between anisotropic and isotropic optical properties is achieved under an around - 6%~- 4% critical strain. The strain controllable electronic and optical properties of the WSSe bilayer may open up an important path for exploring next-generation optoelectronic applications.