van der Waals heterostructure for photocatalysis: Graphitic carbon nitride and Janus transition-metal dichalcogenides

Abstract

Converting solar energy into chemical energy by splitting water is a promising means to generate a sustainable and renewable solution without detrimental environmental impact. The two-dimensional semiconductors serve as potential catalysts in this regard, and here we combine Janus transitionmetal dichalcogenides (MoXY, X/Y = S, Se, Te) and graphitic carbon nitride in a van der Waals heterostructure. Within the first-principles calculations, we investigate the electronic, optical and excitonic properties that determine the photocatalytic activity. Due to the internal electric field, the photogenerated electrons and holes are separated in the MoXY layers, and also generates high overpotentials for the redox reactions. The high optical absorptions span throughout the entire visible and near ultraviolet regime in these heterostructure nanocomposites. Further, the lower exciton binding, calculated within the two-dimensional hydrogenic model, indicates efficient charge separation. Enormous tunability of photocatalytic properties in such heterostructures should attract considerable theoretical and experimental attention in future.

What does graphitic carbon nitride really look like?

“…Indeed, the Van der Waals structures they can form are not just those that are created by stacking with itself, but also by interleaving other species. 41 Within this strategy, interleaving with molybdenum dichalcogenides to allow fast charge separation is of particular experimental 42 and theoretical interest 43 . Here, we focus on the question what particular lamination pattern between gh-C 6 N 9 H 3 layers yields the most stable form of melon.…”

Lifetime of Excitons in Janus Monolayer MoSSe Prepared from Exfoliated MoSe_2

“…Moreover, most theoretical calculations predict even larger exciton transition energies for perfect Janus MoSSe monolayers under ideal conditions. 32,33 We thus conclude, that a trend towards higher energies indicates an improved quality of the material.…”

Engineering 2D Materials for Photocatalytic Water-Splitting from a Theoretical Perspective

“…Due to the separation of photogenerated electron-hole pairs, reaction kinetics, and optical absorption, the heterostructure is widely thought to be a viable solution to large overpotential for HER and OER. As a result, numerous 2D Janus vdW heterojunctions have been designed, such as MoSTe/C 3 N 4 [ 218 ], ZnO/WSSe [ 219 ], MoSSe/SiC [ 220 ], GeC/MoSSe [ 221 ], GaS0.5Se0.5/Arsenene [ 222 ], MoSSe/AlN [ 223 ], MoSSe/GaN [ 223 ], GeC/WSSe [ 221 ], WSSe–SiC [ 220 ], MoSSe/WSSe [ 224 ], MoSSe/C 3 N 4 [ 218 ], and ZnO/MoSSe [ 219 ] heterostructures for photocatalytic water-splitting.…”