Molecular layer-by-layer re-stacking of MoS2-In2Se3 by electrostatic means: assembly of a new layered photocatalyst

2D-layered transition metal chalcogenides are useful semiconductors for a wide range of opto-electronic applications. Their similarity as layered structures offers exciting possibility to modify their electronic properties by creating new heterojunction assemblies from layer-by-layer restacking of individual monolayer sheets, however, the lack of specific interaction between these layers could induce phase segregation. Here, we employed a chemical method using n-BuLi to exfoliate MoS2 and In2Se3 into their monolayer-containing colloids in solution. The bulky Se atoms can be selectively leached from In2Se3 during Li treatment which gives positively charged surface monolayers in neutral pH whereas the strong polarization of Mo-S with moderate S leaching gives a negatively charged surface. Specific interlayer electrostatic attraction during their selective assembly gives a controllable atomic AB-type of layer stacking as supported by EXAFS, STEM with super-EDX mapping, TAS/TRPL and DFT calculations. Using this simple but inexpensive bottom-up solution method, a new photocatalyst assembled from layers for photo water splitting can be tailor-made with high activity.

Automated summary

2D-layered transition metal chalcogenides are semiconductors with a wide range of opto-electronic applications. By creating new heterojunction assemblies from layer-by-layer restacking, their electronic properties can be modified, but the lack of specific interaction between layers could lead to phase segregation. In this study, MoS2 and In2Se3 were exfoliated into monolayer-containing colloids using a chemical method with n-BuLi. The selective leaching of bulky Se atoms from In2Se3 during Li treatment resulted in positively charged surface monolayers, while the strong polarization of Mo-S with moderate S leaching resulted in a negatively charged surface. Specific interlayer electrostatic attraction during selective assembly gave a controllable atomic AB-type layer stacking, as supported by various characterization techniques. This simple and inexpensive bottom-up solution method enables the tailor-made fabrication of a photocatalyst assembled from layers for high activity in photo water splitting.